Allison

CIRCUIT DESCRIPTION:
SS3 is a Normally Closed (N/C) solenoid that provides control main pressure to stroke Shift Valve 3 (SV3) to attain a particular range needed for the next upshift or downshift. A pressure switch is located at the end of the shift valve to send valve position status back to the TCM.

The TCM sends control current to SS3 from High Side Driver 2 (HSD2) via wire 171. HSD2 is continuously on unless the TCM detects a fault condition. The TCM regulates the amount of current to SS3 by switching the low side driver on and off. Wire 151 completes the circuit between SS3 and its low side driver. DTC P0979 indicates that the TCM processor has detected a short-to-battery condition in the low side of the electrical circuit.

ACTION TAKEN WHEN THE DTC SETS:
When the DTC P0979 is active, the following conditions occur:
1. If the failure occurs while in a forward range a shift to 1st, 3rd, or 5th range is made.
2. While diagnostic response is active, if shift selector is moved to N (Neutral), transmission shifts to neutral; if the shift selector is moved to R (Reverse), transmission shifts to reverse. If the shift selector is moved to D (Drive) range or R (Reverse) and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
3. Torque Converter Clutch (TCC) engagement is inhibited.
4. The DTC is stored in the TCM history.
5. The CHECK TRANS light illuminates (non-OBD II strategy).
6. The TCM forces Variable Modulated Main off.
7. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC 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:
The following procedures are not documented in any OEM procedures or in any OEM Troubleshooting or Service information and should not be used as a method to diagnose any transmission DTCs, function, or shift quality concern:

1. Back-probing any connections used for transmission features or functions may damage and/or unlock terminals from the back-probed connector creating permanent or intermittent shorts and/or open circuits. If possible, use the J-39700 Breakout Box, the appropriate harness adapters, and appropriate magnetic overlays to troubleshoot the vehicle.

2. Load-testing any transmission-related circuits with any other electrical devices such as vehicle lamps or relays, especially with the TCM connected to the harness. Use J-39700 Breakout Box and appropriate harnesses with the diagnostic tool to monitor the circuit performance in question unless otherwise specified in the various Troubleshooting information.

3. Piercing a wire to check for voltages, shorts-to-grounds or other wires anywhere in the circuit but especially at the TCM. This creates a leak path for moisture and damages the wire and insulation.

An intermittent circuit condition can allow this DTC to set. Make sure you check for the following conditions at the OEM harness first, then at the transmission internal harness:

Inspect the wiring for poor electrical connections at the TCM and the transmission main connector. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

Inspect OEM wiring harness routing. Look for possible contact points where chafing could occur leading to an open circuit condition. Moving parts on the vehicle could be contacting the harness; this includes parking brake drum, suspension components, transmission shift linkage etc.

When diagnosing for an intermittent open condition, massage the wiring harness while watching the test equipment for a change. It may be necessary to check continuity at individual wires within a harness to isolate an intermittent open condition.

You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time, etc. This data can be useful in reproducing the failure mode when the DTC was set.

CIRCUIT DESCRIPTION:
SS1 is a Normally Closed (N/C) solenoid that provides control main pressure to stroke Shift Valve 1 (SV1) to attain a particular range needed for the next upshift or downshift. A pressure switch is located at the end of the shift valve to send valve position status back to the TCM.

The TCM sends control current to SS1 from High Side Driver 2 (HSD2) via wire 171. HSD2 is continuously on unless the TCM detects a fault condition. The TCM regulates the amount of current to SS1 by switching the low side driver on and off. Wire 152 completes the circuit between SS1 and its low side driver. DTC P097A indicates that the TCM processor has detected an open condition in the electrical circuit. The open condition may exist in the high side (wire 171) or low side (wire 152).

ACTION TAKEN WHEN THE DTC SETS:
When the DTC P097A is active, the following conditions occur:
1. If the failure occurs while in a forward range a shift to 1st, 3rd, or 5th range is made.
2. While diagnostic response is active, if shift selector is moved to N (Neutral), transmission shifts to neutral; if the shift selector is moved to R (Reverse), transmission shifts to reverse. If the shift selector is moved to D (Drive) range or R (Reverse) and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
3. TCC engagement is inhibited.
4. The DTC is stored in the TCM history.
5. The CHECK TRANS light illuminates (non-OBD II strategy).
6. The TCM forces Variable Modulated Main off.
7. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC 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:
The following procedures are not documented in any OEM procedures or in any OEM Troubleshooting or Service information and should not be used as a method to diagnose any transmission DTCs, function, or shift quality concern:

1. Back-probing any connections used for transmission features or functions may damage and/or unlock terminals from the back-probed connector creating permanent or intermittent shorts and/or open circuits. If possible, use the J-39700 Breakout Box, the appropriate harness adapters, and appropriate magnetic overlays to troubleshoot the vehicle.

2. Load-testing any transmission-related circuits with any other electrical devices such as vehicle lamps or relays, especially with the TCM connected to the harness. Use J-39700 Breakout Box and appropriate harnesses with the diagnostic tool to monitor the circuit performance in question unless otherwise specified in the various Troubleshooting information.

3. Piercing a wire to check for voltages, shorts-to-grounds or other wires anywhere in the circuit but especially at the TCM. This creates a leak path for moisture and damages the wire and insulation.

An intermittent circuit condition can allow this DTC to set. Make sure you check for the following conditions at the OEM harness first, then at the transmission internal harness:

DTC P097A indicates an open in the electrical circuit for the SS1. In addition to SS1, HSD2 also supplies power to SS2, PCS2, and SS3. If DTC P097 A is accompanied by DTC P097B and/or DTC P097C and/or DTC P0964, the open is most likely in the high side of the circuit.

Inspect the wiring for poor electrical connections at the TCM and the transmission main connector. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

Inspect OEM wiring harness routing. Look for possible contact points where chafing could occur leading to an open circuit condition. Moving parts on the vehicle could be contacting the harness; this includes parking brake drum, suspension components, transmission shift linkage, etc.

Inspect internal transmission harness wiring for possible contact areas where chafing may occur leading to an open circuit condition.

When diagnosing for an intermittent open condition, massage the wiring harness while watching the test equipment for a change. It may be necessary to check continuity at individual wires within a harness to isolate an intermittent circuit ground condition.

You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time, etc. This data can be useful in reproducing the failure mode where the DTC was set.

CIRCUIT DESCRIPTION:
Shift Solenoid 2 (SS2) is a Normally Closed (N/C) solenoid that provides control main pressure to stroke Shift Valve 2 (SV2) to attain a particular range needed for the next upshift or downshift. A pressure switch is located at the end of the shift valve to send valve position status back to the TCM.

The TCM sends control current to SS2 from High Side Driver 2 (HSD2) via wire 171. HSD2 is continuously on unless the TCM detects a fault condition. The TCM regulates the amount of current to SS2 by switching the low side driver on and off. Wire 133 completes the circuit between SS2 and its low side driver. DTC P097B indicates that the TCM processor has detected an open condition in the electrical circuit. The open condition may exist in the high side (wire 171) or low side (wire 133).

ACTION TAKEN WHEN THE DTC SETS:
When the DTC P097B is active, the following conditions occur:
1. If the failure occurs while in a forward range a shift to 1st, 3rd, or 5th range is made.
2. While diagnostic response is active, if shift selector is moved to N (Neutral), transmission shifts to neutral; if the shift selector is moved to R (Reverse), transmission shifts to reverse. If the shift selector is moved to D (Drive) range or R (Reverse) and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
3. Torque Converter Clutch (TCC) engagement is inhibited.
4. The DTC is stored in the TCM history.
5. The CHECK TRANS light illuminates (non-OBD II strategy).
6. The TCM forces Variable Modulated Main off.
7. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC 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:
The following procedures are not documented in any OEM procedures or in any OEM Troubleshooting or Service information and should not be used as a method to diagnose any transmission DTCs, function, or shift quality concern:

1. Back-probing any connections used for transmission features or functions may damage and/or unlock terminals from the back-probed connector creating permanent or intermittent shorts and/or open circuits. If possible, use the J-39700 Breakout Box, the appropriate harness adapters, and appropriate magnetic overlays to troubleshoot the vehicle.

2. Load-testing any transmission-related circuits with any other electrical devices such as vehicle lamps or relays, especially with the TCM connected to the harness. Use J-39700 Breakout Box and appropriate harnesses with the diagnostic tool to monitor the circuit performance in question unless otherwise specified in the various Troubleshooting information.

3. Piercing a wire to check for voltages, shorts-to-grounds or other wires anywhere in the circuit but especially at the TCM. This creates a leak path for moisture and damages the wire and insulation.

An intermittent circuit condition can allow this DTC to set. Make sure you check for the following conditions at the OEM harness first, then at the transmission internal harness:

DTC P097B indicates an open in the electrical circuit for the SS2. In addition to SS2, HSD2 also supplies power to SS1, PCS2 and SS3. If DTC P097B is accompanied by DTC P097A and/or P097C the open is most likely in the high side of the circuit.

Inspect the wiring for poor electrical connections at the TCM and the transmission main connector. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

Inspect OEM wiring harness routing. Look for possible contact points where chafing could occur leading to an open circuit condition. Moving parts on the vehicle could be contacting the harness; this includes parking brake drum, suspension components, transmission shift linkage etc.

Inspect internal transmission harness wiring for possible contact areas where chafing may occur leading to an open circuit condition.

When diagnosing for an intermittent open condition, massage the wiring harness while watching the test equipment for a change. It may be necessary to check continuity at individual wires within a harness to isolate an intermittent open condition.

You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time, etc. This data can be useful in reproducing the failure mode when the DTC was set.

CIRCUIT DESCRIPTION:
SS3 is a Normally Closed (N/C) solenoid that provides control main pressure to stroke Shift Valve 3 (SV3) to attain a particular range needed for the next upshift or downshift. A pressure switch is located at the end of the shift valve to send valve position status back to the TCM.

The TCM sends control current to SS3 from High Side Driver 2 (HSD2) via wire 171. HSD2 is continuously on unless the TCM detects a fault condition. The TCM regulates the amount of current to SS3 by switching the low side driver on and off. Wire 151 completes the circuit between SS3 and its low side driver. DTC P097C indicates that the TCM processor has detected an open condition in the electrical circuit. The open condition may exist in the high side (wire 171) or low side (wire 151).

ACTION TAKEN WHEN THE DTC SETS:
When the DTC P097C is active, the following conditions occur:
1. If the failure occurs while in a forward range a shift to 1st, 3rd, or 5th range is made.
2. While diagnostic response is active, if shift selector is moved to N (Neutral), transmission shifts to neutral; if the shift selector is moved to R (Reverse), transmission shifts to reverse. If the shift selector is moved to D (Drive) range or R (Reverse) and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
3. Torque Converter Clutch (TCC) engagement is inhibited.
4. The DTC is stored in the TCM history.
5. The CHECK TRANS light illuminates (non-OBD II strategy).
6. The TCM forces Variable Modulated Main off.
7. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC 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:
The following procedures are not documented in any OEM procedures or in any OEM Troubleshooting or Service information and should not be used as a method to diagnose any transmission DTCs, function, or shift quality concern:

1. Back-probing any connections used for transmission features or functions may damage and/or unlock terminals from the back-probed connector creating permanent or intermittent shorts and/or open circuits. If possible, use the J-39700 Breakout Box, the appropriate harness adapters, and appropriate magnetic overlays to troubleshoot the vehicle.

2. Load-testing any transmission-related circuits with any other electrical devices such as vehicle lamps or relays, especially with the TCM connected to the harness. Use J-39700 Breakout Box and appropriate harnesses with the diagnostic tool to monitor the circuit performance in question unless otherwise specified in the various Troubleshooting information.

3. Piercing a wire to check for voltages, shorts-to-grounds or other wires anywhere in the circuit but especially at the TCM. This creates a leak path for moisture and damages the wire and insulation.

An intermittent circuit condition can allow this DTC to set. Make sure you check for the following conditions at the OEM harness first, then at the transmission internal harness:

DTC P097C indicates an open in the electrical circuit for SS3. In addition to SS3, HSD2 also supplies power to SS1, PCS2 and SS2. If DTC P097C is accompanied by DTC P097A and/or DTC P097B and/or DTC P0964, the open is most likely in the high side of the circuit.

Inspect the wiring for poor electrical connections at the TCM and the transmission main connector. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

Inspect OEM wiring harness routing. Look for possible contact points where chafing could occur leading to an open circuit condition. Moving parts on the vehicle could be contacting the harness; this includes parking brake drum, suspension components, transmission shift linkage etc.

Inspect internal transmission harness wiring for possible contact areas where chafing may occur leading to an open circuit condition.

When diagnosing for an intermittent open condition, massage the wiring harness while watching the test equipment for a change. It may be necessary to check continuity at individual wires within a harness to isolate an intermittent open condition.

You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time, etc. This data can be useful in reproducing the failure mode when the DTC was set.

CIRCUIT DESCRIPTION:
SS3 is a Normally Closed (N/C) solenoid that provides control main pressure to stroke Shift Valve 3 (SV3) to attain a particular range needed for the next upshift or downshift. A pressure switch is located at the end of the shift valve to send valve position status back to the TCM.

The TCM sends control current to SS3 from High Side Driver 2 (HSD2) via wire 171. HSD2 is continuously on unless the TCM detects a fault condition. The TCM regulates the amount of current to SS3 by switching the low side driver on and off. Wire 151 completes the circuit between SS3 and its low side driver. DTC P0980 indicates that the TCM processor has detected a short-to-battery condition in the low side of the electrical circuit.

ACTION TAKEN WHEN THE DTC SETS:
When the DTC P0980 is active, the following conditions occur:
1. If the failure occurs while in a forward range a shift to 1st, 3rd, or 5th range is made.
2. While diagnostic response is active, if shift selector is moved to N (Neutral), transmission shifts to neutral; if the shift selector is moved to R (Reverse), transmission shifts to reverse. If the shift selector is moved to D (Drive) range or R (Reverse) and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
3. Torque Converter Clutch (TCC) engagement is inhibited.
4. The DTC is stored in the TCM history.
5. The CHECK TRANS light illuminates (non-OBD II strategy).
6. The TCM forces Variable Modulated Main off.
7. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC 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:
The following procedures are not documented in any OEM procedures or in any OEM Troubleshooting or Service information and should not be used as a method to diagnose any transmission DTCs, function, or shift quality concern:

1. Back-probing any connections used for transmission features or functions may damage and/or unlock terminals from the back-probed connector creating permanent or intermittent shorts and/or open circuits. If possible, use the J-39700 Breakout Box, the appropriate harness adapters, and appropriate magnetic overlays to troubleshoot the vehicle.

2. Load-testing any transmission-related circuits with any other electrical devices such as vehicle lamps or relays, especially with the TCM connected to the harness. Use J-39700 Breakout Box and appropriate harnesses with the diagnostic tool to monitor the circuit performance in question unless otherwise specified in the various Troubleshooting information.

3. Piercing a wire to check for voltages, shorts-to-grounds or other wires anywhere in the circuit but especially at the TCM. This creates a leak path for moisture and damages the wire and insulation.

4. DTC P0980 indicates a short-to-battery in the electrical circuit for SS3.

Inspect the wiring for poor electrical connections at the TCM and the transmission main connector. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

Inspect OEM wiring harness routing. Look for possible contact points where chafing could occur leading to an open circuit condition. Moving parts on the vehicle could be contacting the harness; this includes parking brake drum, suspension components, transmission shift linkage etc.

When diagnosing for an intermittent open condition, massage the wiring harness while watching the test equipment for a change.

You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time, etc. This data can be useful in reproducing the failure mode when the DTC was set.

CIRCUIT DESCRIPTION:
This DTC sets if the TCM determines the primary shift selector calibration is invalid.

ACTION TAKEN WHEN THE DTC SETS:
1. The CHECK TRANS light illuminates.
2. DTC is stored in the TCM history.
3. Display may be in the wrong language and/or units (English/Metric) could be formatted incorrectly.

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.

DIAGNOSTIC AIDS:
None

CIRCUIT DESCRIPTION:
The TCM can be calibrated to receive throttle information from a PWM signal. DTC P1891 sets when the TCM detects PWM throttle signal less than calibrated percent for a calibrated time.

ACTION TAKEN WHEN THE DTC SETS:
When the DTC P1891 is active, the following conditions occur:
1. The CHECK TRANS light is not illuminated (non-OBD II strategy).
2. The DTC is stored in the TCM history.
3. The TCM freezes shift adapts (DNA).
4. TCM uses default throttle values.
5. The TCM forces Variable Modulated main off.
6. TCM inhibits the Torque Converter Clutch (TCC).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC for the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
The TCM detects the throttle source automatically during the initial series of engine starts. The TCM may have auto-detected the wrong throttle source type. Use the diagnostic tool to reset auto-detect or select the appropriate throttle source if PWM-type sensor is not being used.

Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.

You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time etc. This data can be useful in reproducing the failure mode where the DTC was set.

CIRCUIT DESCRIPTION:
The TCM can be calibrated to receive throttle information from a Pulse Width Modulated (PWM) signal. DTC P1891 sets when the TCM detects PWM throttle signal greater than calibrated percent for a calibrated time.

ACTION TAKEN WHEN THE DTC SETS:
When the DTC P1892 is active, the following conditions occur:
1. The CHECK TRANS light is not illuminated (non-OBD II strategy).
2. The DTC is stored in the TCM history.
3. The TCM freezes shift adapts (DNA).
4. TCM uses default throttle values.
5. The TCM forces Variable Modulated main off.
6. TCM inhibits the Torque Converter Clutch (TCC).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC for the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
The TCM detects the throttle source automatically during the initial series of engine starts. The TCM may have auto-detected the wrong throttle source type. Use the diagnostic tool to reset auto-detect or select the appropriate throttle source if PWM-type sensor is not being used.

Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.

You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time etc. This data can be useful in reproducing the failure mode where the DTC was set.

CIRCUIT DESCRIPTION:
SEM allows the TCM to request torque reduction from the engine controller. By reducing torque, shifts can be made quicker, at a more consistent output torque which reduces clutch temperature and increases clutch life. DTC P2637 sets when the TCM detects one of the following conditions for a minimum of four upshifts (consecutive or nonconsecutive) during one drive cycle:
1. Engine Control Module (ECM) is not responding to SEM torque reduction signal request from the TCM.
2. A non-approved J1939 device is interfering with the SEM torque reduction signal request.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P2637 is active, the following conditions occur:
1. The CHECK TRANS light illuminates (non-OBD II strategy).
2. The TCM forces Variable Modulated Main off.
3. The TCM will not allow full throttle 3rd to 4th, 4th to 5th range or 5th to 5th range upshifts.
4. The DTC is stored in the TCM history.

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC 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:
1. Poor engine performance can allow this code to set. Have the OEM inspect for possible exhaust manifold pressure sensor concern or other engine related subsystems.
2. It will be necessary to drive the vehicle with heavy to moderate throttle settings for at least four upshift cycles in order to set DTC P2637.
3. If DTC P0614 is set in combination with DTCs P2637 and/or DTC P2641, engine control software is not correct. Verify the proper software is installed.