PDF Troubleshooting Manual Allison Transmission 1000 & 2000 Series Electronic Controls - 1 MB

Diagnose and resolve issues with your Allison 1000 and 2000 series transmissions using this electronic controls troubleshooting manual.

This highly detailed guide provides diagnostic codes, troubleshooting flowcharts, and repair procedures.

It is an essential resource for technicians working on the complex electronic control systems of these transmissions.

Solve problems efficiently and accurately with this expert manual.

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--- Page 1 ---
1000/2000/2400 ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
                                  PREFACE


Welcome to the TS3192EN Troubleshooting Manual. We make every effort to keep our service
information current and accurate. Because of the time lag involved with writing and printing processes,
the transmission TCM may report a code that has not yet been added to this document. If you encounter
a code that is not yet in this publication, please call the Allison Transmission Technical Assistance Center
at 1-800-252-5283.

Go to the Table of Contents.


                                       Copyright© 2004 General Motors Corp.

--- Page 3 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                                    GENERAL DESCRIPTION
           The TCM shift calibration determines the available forward ranges for each selector position.
           Although specific installations vary, typical selector positions for the 1000 and 2000 Product
           Families are:

           P — Park. Parking pawl or parking brake is engaged, if available. This position is not available
           on all shift selectors.
           R — Reverse.
           N — Neutral. May be used when starting the engine and for stationary operations. The NSBU
           Switch disables the starter switch if a range other than N (Neutral) or P (Park) is selected before
           starting the vehicle.
           OD — Overdrive. The highest forward range used for normal driving. The transmission shifts to
           first range for starting, then automatically upshifts through the ranges (as operating conditions
           permit) until the highest range is attained.
           D, 2, 1 — Forward Range. The transmission shifts to first range for starting. The range selected
           on the shift selector is the highest range which will be attained during automatic shifting.

      B.   Manual Selector Valve
           The manual shift selector shaft is attached to the manual selector valve within the transmission
           main control valve body. The selector valve has three positions: Reverse, Neutral, and Forward.

           NOTE: For transmissions equipped with a Park position, the selector valve remains in
                 the Neutral position when the selector is moved to Park.

           The Neutral and Reverse selector valve positions (refer to Appendix H—Hydraulic Schematics)
           exhaust the C1 and C2 rotating clutches. By exhausting C1 and C2 clutches, forward range is
           inhibited. This provides the capability for the operator to override the electronically commanded
           ranges if N (Neutral) is required.

      C.   NSBU Switch
           The installation of a transmission-mounted neutral start/reverse signal switch is required. This
           switch, commonly called an “NSBU Switch” (Figure 1–5), mounts directly onto the transmission
           housing from the outside and detects the angular position of the shift selector shaft. This
           position is communicated to the TCM so that certain vehicle control functions can be
           coordinated with the position of the shift controls. The NSBU switch has redundant circuitry to
           alert the TCM in the event of a single wire or switch failure.

           The neutral signal output of the NSBU switch is typically used as confirmation that the
           transmission is in N (Neutral) before the engine starter is engaged. The NSBU switch is
           interfaced to the starter circuit with weatherproof electrical connectors. The reverse signal
           provision may be used to activate vehicle back-up lights and/or reverse warning devices.


                                                                                                           V05729.01.00


                                          Figure 1–5. NSBU Switch


1–4                                 Copyright© 2004 General Motors Corp.

--- Page 4 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                       DEFINITIONS AND ABBREVIATIONS

2–4.    ABBREVIATIONS
 A/N           Assembly Number
 ABS           Anti-lock Brake System—OEM-provided means to detect and prevent wheel stoppage to
               enhance vehicle handling. Retarder and engine brakes will not apply when ABS is active.
 Amp           Ampere—Unit of electrical current
 CAN           Controller Area Network—A network for all SAE J1939 communications in a vehicle
               (engine, transmission, diagnostics, ABS, etc.)
 CC            Calibration Compatibility—First two digits of the CIN
 CIN           Calibration Identification Number—Used to identify transmission controls software level
 CT            Closed Throttle
 DNA           Does Not Adapt—Adaptive shift control is disabled.
 DNS           DO NOT SHIFT—Refers to the DO NOT SHIFT diagnostic response during which the
               CHECK TRANS light is illuminated and the transmission will not shift and will not respond
               to the Shift Selector.
 DTC           Diagnostic Trouble Code
 DVOM          Digital volt/ohmmeter
 ECM           Engine Controller Module—Available on electronically-controlled engines—provides some
               relevant data to TCM.
 EMI           ElectroMagnetic Interference
 GPI           General Purpose Input—Input signal to the TCM to request a special operating mode or
               condition.
 GPO           General Purpose Output—Output signal from the TCM to control vehicle components
               (such as PTOs, backup lights, etc.) or allow a special operating mode or condition.
 IPC           Instrument Panel Controller
 J1939         High-speed vehicle serial data communications link.
 LED           Light-Emitting Diode—Electronic device used for illumination.
 LRTP          Low-Range Torque Protection—A feature limiting engine torque in lower ranges to protect
               the transmission from damage when a stall condition occurs.
 NNC           Neutral No Clutches—Neutral commanded with no clutches applied.
 NSBU Switch   Neutral Start Backup Switch
 NVL           Neutral Very Low—The TCM has sensed turbine speed below 150 rpm. This is usually
               caused by a dragging C1 or C3 clutch or a failed turbine speed sensor. When attained, the
               C4 and C5 clutches are applied to lock the transmission output.
 OBD II        On Board Diagnostics Second generation. EPA mandated specification for vehicle
               diagnostics.
 OEM           Original Equipment Manufacturer—Maker of vehicle or equipment.
 Ohm           Unit of electrical resistance.
 PC            Personal Computer
 PCCS          Production Calibration Configuration System
 PCM           Powertrain Controller Module—Electronic device used on some vehicles.
 PDM           Parallel Data Module


2–4                              Copyright© 2004 General Motors Corp.

--- Page 5 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                                          BASIC KNOWLEDGE
        PCCS Load Station is used to reset Autoselect function, to do this it is necessary to clear all power-off data
        currently stored in the TCM.
             • Go to the Maintenance button and select “Erase Power-off Data”
             • After selecting “Erase Power-off data”, a message will indicate “PCCS is going to erase Power-off
               data”. Select “Yes”. Selecting “No” will abort the clearing of Power-off Data.
             • After clearing Power-off Data, there will be a prompt to cycle the ignition.
        The TCM is now reset to Autoselect and will start looking for supporting engine software.
        Drive the vehicle; confirm DTCs have not returned.

NOTE:     Transmission shifts will now be in the unadaptive (base) state, so it will be necessary to drive the
          vehicle to allow shifts to converge.
        Autoselect reset function will be incorporated into the Allison DOC™ For PC service tool at a later date,
        along with an indication of the current SEM Autoselect status.


3–8                                   Copyright© 2004 General Motors Corp.

--- Page 6 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                         DIAGNOSTIC TROUBLE CODES (DTC)
5–5.    DIAGNOSTIC TROUBLE CODES (DTCs)
                       DTC LIST AND DESCRIPTION INDEX
                                                                                   CHECK
                                                                                   TRANS
 DTC                                       Description                              Light    Page
P0122  Pedal Position Sensor Circuit Low Voltage                                     Yes    5–16
P0123  Pedal Position Sensor Circuit High Voltage                                    Yes    5–20
P0218  Transmission Fluid Over Temperature Condition                                 No     5–24
P0561  Unrealistic Variations In Vehicle System Voltage                              Yes    5–27
P0562  System Voltage Low                                                            Yes    5–31
P0563  System Voltage High                                                           Yes    5–34
P0602  TCM Not Programmed                                                            Yes    5–37
P0606  Controller Internal Performance—Not enabled for Pickups or med duty “04”      Yes    5–38
P0614  Torque Control Data Mismatch—ECM/TCM                                          Yes    5–39
P0701  Transmission Control System Performance                                       No     5–41
P0703  Brake Switch Circuit Malfunction—GMT800 only                                  No     5–43
       Transmission Range Sensor Circuit (PNRDL input)
P0705âśť                                                                              N/A
       Not production enabled/could be in development cals
       Transmission Range Sensor Circuit (Performance)
P0706âśť                                                                              N/A
       Not production enabled/could be in development cals
P0708 Transmission Range Sensor Circuit High Input                                  Yes     5–46
       Transmission Fluid Temperature Sensor Circuit
P0710âśť                                                                              N/A
       Not production enabled/could be in development cals
P0711 Transmission Fluid Temperature Sensor Circuit Performance                     No      5–50
P0712 Transmission Fluid Temperature Sensor Circuit Low Input (High Temperature)    No      5–54
P0713 Transmission Fluid Temperature Sensor Circuit High Input (Low Temperature)    No      5–58
P0716 Turbine Speed Sensor Circuit Performance                                      Yes     5–62
P0717 Turbine Speed Sensor Circuit No Signal                                        Yes     5–65
P0719 Brake Switch ABS Input Low                                                    N/A     5–69
P0721 Output Speed Sensor Circuit Performance                                       Yes     5–71
P0722 Output Speed Sensor Circuit No Signal                                         Yes     5–75
P0726 Engine Speed Input Circuit Performance                                        No      5–79
P0727 Engine Speed Input Circuit No Signal                                          No      5–82
P0731 Incorrect 1st Gear Ratio                                                      Yes     5–85
P0732 Incorrect 2nd Gear Ratio                                                      Yes     5–88
P0733 Incorrect 3rd Gear Ratio                                                      Yes     5–91
P0734 Incorrect 4th Gear Ratio                                                      Yes     5–94
P0735 Incorrect 5th Gear Ratio                                                      Yes     5–97
P0736 Incorrect Reverse Ratio                                                       Yes     5–100
P0741 Torque Converter Clutch System Stuck Off                                      Yes     5–104
P0742 Torque Converter Clutch System Stuck On                                       Yes     5–107
P0743 Torque Converter Clutch PWM Solenoid Circuit—Electrical (Previously P1860)    Yes     5–110
P0746 Solenoid A Controlled Clutch Stuck Off (Previously P1720)                     Yes     5–115
P0747 Solenoid A Controlled Clutch Stuck On (Previously P1723)                      Yes     5–118
P0748 Pressure Control Solenoid A Electrical                                        Yes     5–121
P0763 Shift Solenoid C Electrical                                                   Yes     5–126


5–6                              Copyright© 2004 General Motors Corp.

--- Page 7 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                              DIAGNOSTIC TROUBLE CODES (DTC)
                        DTC P0122 Pedal Position Sensor Circuit Low Voltage


                                     J2 HARNESS CONNECTOR
                                             (RED)
                                                                J2-9


                                                                                             TCM
                  TPS
               CONNECTOR
                                                      J2-20            J2-19


                                                                         J2

                                                                                       J1
                                         A
                                     B
                                 C


                                                              219
                                                  C                            J2-19    5V
                                                                                              TCM
                            THROTTLE                          209                       ANALOG
                            POSITION              B                            J2-9
                                                                                        INTERFACE
                             SENSOR
                              (TPS)                           220
                                                  A                            J2-20


                                                                                                        V06225.01.00


Circuit Description

The Transmission Control Module (TCM) receives input on throttle position from either a Throttle Position Sensor
(TPS) or a signal transmitted by the engine electronic controls.

Vehicles not equipped with electronically-controlled engines have a TPS attached to the engine fuel control linkage.
The TPS continuously sends the exact throttle position to the transmission TCM.

The TPS is a sliding resistor sensor (potentiometer) actuated by a mechanical linkage. The TCM delivers a
constant voltage to one terminal of the TPS resistive strip. The other TPS terminal connects to ground. The resistor
contacts of the TPS are connected to provide a regulated voltage signal input to the TCM.

When actuated by the mechanical throttle cable, the contacts of the resistor move along the resistive strip. As the
contacts slide along the resistive strip, a voltage is sent to the TCM. At each increment of 0.178 mm (0.007 inch)
along the resistive strip, the contacts deliver a different voltage to the TCM. The different voltages are interpreted as
throttle sensor movement. The TCM converts travel distance (mm) into throttle opening percentage.

Conditions for Running the DTC
•   The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater
    than 18V and less than 32V (24V TCM).
•   DTC P0123 Pedal Position Sensor Circuit High Voltage is not active.

5–16                                         Copyright© 2004 General Motors Corp.

--- Page 8 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                             DIAGNOSTIC TROUBLE CODES (DTC)

              DTC P0218 Transmission Fluid Over Temperature Condition (cont’d)
 Step                             Action                                        Yes                    No
  2   1. Install  the Scan Tool.                                            Go to Step 3         Go to A/T Fluid
      2. Turn ON the ignition, with the engine OFF.                                            Checking Procedure.
      3. Record the Failure Record data.                                                          (Appendix P)
      4. Clear the DTC.
      5. Perform the A/T Fluid Checking Procedure (Appendix P).
      Was the A/T fluid level check performed?
  3   1. Inspect the engine cooling system for the following                Go to Step 6          Go to Step 4
         conditions:
         • Air flow restrictions
         • Air flow blockage
         • System fluid level and condition
         • Debris
      2. Inspect the transmission cooling system for the following
         conditions:
         • Air flow restrictions
         • Air flow blockage
         • System fluid level and condition
         • Debris
         • Damaged cooler lines or hoses
      Did you find and correct the condition?
  4   Perform    the Main Pressure Check Procedure. Refer to                Go to Step 6          Go to Step 5
      Appendix B.
      Did you find and correct a pressure problem?
  5   Check   for a possible torque converter stator malfunction.           Go to Step 6          Go to General
      A stuck stator would be indicated by no cool-down in neutral                               Troubleshooting
      after stalling the transmission. Refer to Section 7.                                         (Section 7)
      Did you find and correct the condition?
  6   Perform the following procedure in order to verify your            Begin the diagnosis       System OK
      repair:                                                                   again.
      1. Clear the DTC.                                                     Go to Step 1
      2. Using the Scan Tool, monitor the transmission fluid
         temperature.
      3. Operate the vehicle under the following conditions.
      4. Turn ON the ignition, with the engine OFF.
      5. The TFT must be less than 126°C (258°F) for at least
         10 seconds.
      6. Using the Scan tool, verify that the test to detect this code
         has run.
      Has the test run and passed?


5–26                                  Copyright© 2004 General Motors Corp.

--- Page 9 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                            DIAGNOSTIC TROUBLE CODES (DTC)
                               DTC P0563 System Voltage High (cont’d)
Step                      Action                              Value(s)             Yes                No
 2   1. Install the Scan Tool.                           See Conditions for    Go to Step 4       Go to Step 3
     2. Turn ON the ignition, with the engine OFF.        Setting the DTC
     3. Record the failure records.
     4. Clear the DTC.
     5. Start vehicle engine and inspect the ignition
        voltage value on the Scan Tool.
       NOTE: This DTC sets when ignition voltage
       is detected above 18V for 12V systems or
       32V for 24V systems for 6 out of 10 seconds.
        Is the ignition voltage above specified value?
  3    1. Start the vehicle, if possible.                        —             Go to Step 4      Go to Diagnostic
       2. If the DTC is not active, drive the vehicle.                                                 Aids
          Attempt to duplicate the same operating
          conditions observed in failure records.
       Did the DTC return?
  4    Test the vehicle charging system per the OEM              —            Go to Diagnostic     Repair the
       recommended testing procedure.                                               Aids         charging system
       Is the charging system operating properly?                                                and go to Step 5
  5    In order to verify your repair:                           —               Begin the         System OK
       1. Clear DTC.                                                          diagnosis again.
       2. Drive vehicle under conditions shown in                               Go to Step 1
          failure records when DTC set.
       Did the DTC return?


5–36                                 Copyright© 2004 General Motors Corp.

--- Page 10 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                                 DIAGNOSTIC TROUBLE CODES (DTC)
                    DTC P0708 Transmission Range Sensor Circuit High Input

                 J2 HARNESS CONNECTOR
                         (RED)                                                        TCM
                          J2-7             J2-6
                         J2-8              J2-5


                                                                        J2

                                             J2-20                               J1

                                                           4-PIN AND 7-PIN

                            NSBU SWITCH                                                     TCM
                                                                  208
                                   P              4C   8                     J2-8
                                                                  207
                                   C              4B   6                     J2-7
                                                                                            DIGITAL
                                                                  206                       INTERFACE
                                   B              4D   4                     J2-6
                                                                  205
                                   A              4A   5                     J2-5
                                                                  220
                                                  7D   7                     J2-20      GND

                                                              12-PIN
                                                              SINGLE CONNECTOR
                                                              NSBU
                                          FORMER                                        CURRENT
                                       NSBU SWITCH                                    NSBU SWITCH
                                       4- AND 7-PIN                                      12-PIN


                                                                                                        V06217.01.00


Circuit Description
The installation of a transmission-mounted Neutral Start/Back-Up (NSBU) switch is required. This switch mounts
directly onto the transmission housing from the outside and detects the angular position of the shift selector shaft.
This position is communicated to the Transmission Control Module (TCM) so that certain vehicle control functions
can be coordinated with the position of the shift controls. The NSBU switch has redundant circuitry to alert the TCM
in the event of a single wire or switch failure.

The neutral signal output of the NSBU switch is typically used as confirmation that the transmission is in
N (Neutral) before the engine starter is engaged. The NSBU switch is interfaced to the starter circuit with
weatherproof electrical connectors. The reverse signal provision may be used to activate vehicle back-up lights
and/or reverse warning devices.

Conditions for Running the DTC
•   The components are powered and ignition voltage is greater than 9V and less than 18V.
•   Engine speed is greater than 200 rpm and less than 7500 rpm for 5 seconds.

5–46                                     Copyright© 2004 General Motors Corp.

--- Page 11 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                            DIAGNOSTIC TROUBLE CODES (DTC)

            DTC P0712 Transmission Fluid Temperature Sensor Circuit Low Input
                                  (High Temperature)
Step                   Action                                 Value(s)            Yes                 No
 1   Was the Beginning The Troubleshooting                       —            Go to Step 2           Go to
     Process (Paragraph 5–4A) performed?                                                         Beginning The
                                                                                                Troubleshooting
                                                                                                    Process
                                                                                               (Paragraph 5–4A)
  2    Perform the A/T Fluid Checking Procedure                  —            Go to Step 3      Go to A/T Fluid
       (Appendix P).                                                                                Checking
       Is the transmission fluid level correct?                                                    Procedure
                                                                                                  (Appendix P)
  3    1. Turn the ignition OFF.                            4.75–5.25V        Go to Step 4       Go to Step 11
       2. Disconnect J2 connector at the TCM and
          install J 39700 Breakout Box and J 43799
          Breakout Box Adapter at J2 connector.
       3. With the engine OFF, turn the ignition to the
          ON position. Measure voltage at J2
          connector pins 10 and 20.
       Is voltage within the specified value?
  4    1. Install the Scan Tool.                           150°C (302°F)      Go to Step 5         Go to
       2. With the engine OFF, turn the ignition to the                                        Diagnostic Aids
          ON position.
       3. Record the Failure Record data.
       4. Clear the DTC.
       5. Select TFT on the Scan Tool. Drive the
          vehicle and inspect for unrealistic TFT
          readings.
       Is the TFT reading at or above the specified
       value?
       This DTC may indicate a short to ground at wire
       210.
  5    1. Disconnect the wiring harness from the main     3398–3582 Ohms      Go to Step 6       Go to Step 8
          transmission connector.                          at 20°C (68°F)
       2. Using a DVOM, measure resistance at main             Refer to
          transmission connector pins G and H.*             TFT Sensor
       Is resistance within the specified values?         Resistance Table
                                                             Page 5–13)
  6    1. Reconnect the wiring harness to the main        3398–3582 Ohms         Go to           Go to Step 7
          transmission connector.                          at 20°C (68°F)    Diagnostic Aids
       2. Disconnect J2 connector from the TCM.                Refer to
       3. Using a DVOM, measure resistance at J2            TFT Sensor
          connector pins 10 and 20.                       Resistance Table
       Is the resistance within the specified values?        Page 5–13)


5–56                                 Copyright© 2004 General Motors Corp.

--- Page 12 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                             DIAGNOSTIC TROUBLE CODES (DTC)
•   When unrealistic low turbine speed is detected.
    — Engine is running.
    — Shift is not in process.
    — Range attained is not neutral.
    — Transmission fluid temperature is above –25°C (–13°F).
    — Transmission output speed is at or above 150 rpm or engine speed is at or above 400 rpm.

Conditions for Setting the DTC

DTC P0717 is set when one of the following conditions occur:
•   Unrealistic large change in turbine speed. A Failure pending is set if an unrealistic change in transmission
    turbine speed is detected at or above 800 rpm. The failure pending response is to lock in the current range.
•   Unrealistic low value in turbine speed. A failure pending is set if turbine speed is detected below 61 rpm. A
    failure is set when turbine speed is below 61 rpm and output speed is detected above 500 rpm for more than
    1 second.

Action Taken When the DTC Sets
•   When DTC P0717 is active, the following conditions will occur:
    — If failure occurs while in a forward range and a shift has been completed, the transmission will remain in the
      current range.
    — If failure occurs while in a forward range and a shift is in progress, the transmission will return to the
      previous range, except in post-shift state; then the transmission will continue to the commanded range.
    — If failure occurs under other conditions, the transmission shifts to 1st, 3rd, or 5th.
    — If the shift selector is moved to N (Neutral), R (Reverse), or any other forward range, the transmission will
      lock in N (Neutral).
•   DTC P0717 is stored in the TCM history.
•   The CHECK TRANS light illuminates.
•   The TCM freezes shift adapts (DNA).
•   The TCM inhibits TCC engagement.

Conditions for Clearing the DTC/CHECK TRANS Light
A Scan Tool may be used to clear the code from the TCM history. The TCM automatically clears the DTC from the
TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

Diagnostic Aids
•   Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
    — A bent terminal.
    — A backed-out terminal.
    — A damaged terminal.
    — Poor terminal tension.
    — A chafed wire.
    — A broken wire inside the insulation.
•   You may have to drive the vehicle in order to experience a fault.

5–66                                  Copyright© 2004 General Motors Corp.

--- Page 13 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                             DIAGNOSTIC TROUBLE CODES (DTC)
•   When unrealistically low output speed is detected.
    — Engine is running.
    — Shift is not in process.
    — Range attained is not neutral.
    — Transmission fluid temperature is above –25°C (–13°F).
    — Transmission turbine speed is at or above 1050 rpm.
    — Manual selector valve is not being moved to a forward range.

Conditions for Setting the DTC
DTC P0722 is set when one of the following conditions occur:
•   Unrealistic large change in output speed. A failure pending is set if an unrealistic change in transmission output
    speed is detected at or above 600 rpm. A failure is set if neutral range is attained.
•   Unrealistic low value in output speed. A failure pending is set if output speed is detected below 61 rpm. A
    failure is set when output speed is below 61 rpm and transmission range is 3rd, 4th, or 5th for more than
    1 second.

Action Taken When the DTC Sets
•   When DTC P0722 is active, the following conditions will occur:
    — If failure occurs while in a forward range and a shift has been completed, the transmission will remain in the
      current range.
    — If failure occurs while in a forward range and a shift is in progress, the transmission will return to the
      previous range, except in post-shift state; then the transmission will continue to the commanded range.
    — If failure occurs under other conditions, the transmission shifts to 1st, 3rd, or 5th.
    — If the shift selector is moved to N (Neutral), R (Reverse), or any other forward range while the diagnostic
      response is active, the transmission will lock in N (Neutral).
    — If a latched inhibit is present, the transmission locks in neutral.
•   DTC P0722 is stored in the TCM history.
•   The CHECK TRANS light illuminates.
•   The TCM freezes shift adapts (DNA).
•   The TCM inhibits TCC engagement.

Conditions for Clearing the DTC/CHECK TRANS Light
A Scan Tool may be used to clear the code from the TCM history. The TCM automatically clears the DTC from the
TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

Diagnostic Aids
•   Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
    — A bent terminal.
    — A backed-out terminal.
    — A damaged terminal.
    — Poor terminal tension.
    — A chafed wire.
    — A broken wire inside the insulation.
•   You may have to drive the vehicle in order to experience a fault.

5–76                                  Copyright© 2004 General Motors Corp.

--- Page 14 ---
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

                               DIAGNOSTIC TROUBLE CODES (DTC)
Test Description
The numbers below refer to the step numbers on the diagnostic table.
       3. This step tests ignition voltage.
       4. This step tests for current first range ratio.
       5. This step tests speed sensor readings.
       6. This step tests for clutch slippage in first range.
       7. This step checks for evidence of clutch failure.

                                     DTC P0731 Incorrect 1st Gear Ratio
 Step                       Action                                Value(s)           Yes               No
  1       Was the Beginning The Troubleshooting                      —           Go to Step 2         Go to
          Process (Paragraph 5–4A) performed?                                                     Beginning The
                                                                                                 Troubleshooting
                                                                                                     Process
                                                                                                (Paragraph 5–4A)
   2      Perform the A/T Fluid Checking Procedure                   —           Go to Step 3    Go to A/T Fluid
          (Appendix P) and correct the fluid level if                                                Checking
          necessary.                                                                                Procedure
          Did you perform the procedure?                                                           (Appendix P)
   3      1. Start the engine.                                      9–18V        Go to Step 4       Resolve
          2. Record the DTC Failure Record data.                 (12V TCM);                     voltage problem

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