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P2796




DTC P0B09 or P2796

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC P0B09
- Auxiliary Transmission Fluid Pump Positive Voltage Relay Control Circuit

DTC P2796
- Auxiliary Transmission Fluid Pump Control Circuit

Diagnostic Fault Information





Circuit/System Description

The auxiliary transmission fluid pump is an electrical device that is used with the auxiliary transmission fluid pump relay to maintain transmission fluid line pressure to the transmission during Engine Idle Off mode. The ECM monitors the transmission fluid pressure switch (TFP) to verify that the auxiliary transmission pump is maintaining the proper amount of pressure. The auxiliary transmission fluid pump attaches to the transmission side cover assembly. The auxiliary transmission fluid pump relay receives voltage through the battery positive voltage circuit. The starter generator control module (SGCM) controls the auxiliary pump by providing the ground path on the transmission pump relay coil control circuit, sending power to the automatic transmission auxiliary fluid pump control module (AFPCM). The SGCM monitors all of the circuits of the AFPCM.

Conditions for Running the DTC

The Hybrid Wake Up signal is ON.

Conditions for Setting the DTC

P0B09
* The SGCM detects an open, short to ground, or short to voltage on the transmission pump relay coil control circuit for 320 milliseconds.
* The SGCM detects an open, short to ground, or short to voltage on the hybrid control module pump control circuit between the SGCM and the AFPCM for 320 milliseconds.

P2796

SGCM detects an open or short to ground in the transmission pump switch control circuit.

Action Taken When the DTC Sets

* DTCs P0B09 and P2796 are Type B DTCs.
* The SGCM inhibits Auxiliary Transmission Pump Relay control.
* The SGCM inhibits auxiliary transmission fluid pump operation.
* The SGCM inhibits Hybrid operation.

Conditions for Clearing the DTC

DTCs P0B09 and P2796 are Type B DTCs.

Diagnostic Aids

It is possible to have loose connectors at the AFPCM and the SGCM that may set these DTCs. Be sure connectors are fully engaged.

Reference Information
Schematic Reference

* Automatic Transmission Controls Schematics (4T45-E - Automatic Transmission)
* Hybrid Cooling Schematics ()

Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Starter/Generator Description and Operation ()
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

* J 35616 - GM-Approved Terminal Test Kit
* EL-49741 - 9 V+ Power Source Harness

Circuit/System Verification

1. Verify that the Trans Pump MTR fuse, underhood fuse block - fuse 52, is not open.
2. Key ON. Engine OFF.
3. Using a scan tool, command the Aux. Trans. Pump ON and OFF. When commanded ON you should be able to hear the auxiliary transmission fluid pump running. When commanded OFF the auxiliary transmission fluid pump should stop running. A stethoscope may be necessary to hear pump running.

Circuit/System Testing

1. Key OFF.
2. Verify all connectors at the, SGCM, AFPCM, and automatic transmission fluid pump are fully engaged.
3. Disconnect the X1 connector at the SGCM.
4. Using the BN probe J 35616-6, test for B+ (+0.0/-1.0 V) between the transmission pump relay coil control circuit, SGCM X1 pin 2 and a good ground.

• If the voltage is less than the specified value, test the transmission pump relay coil control circuit for an open/high resistance or short to ground condition, and the transmission pump switch control circuit for a short to ground. If all circuits and connections test normal, test the Pump MTR Relay.

5. Connect the X1 connector at the SGCM.
6. Disconnect the X1 connector at the automatic transmission auxiliary fluid pump control module (AFPCM).
7. Remove the Trans Pump MTR Relay, underhood fuse block relay 53.
8. Key ON. Engine OFF.
9. Using the PU probe J 35616-4A, test for less than 10 ohm between the two ends of the transmission pump switch control circuit, underhood fuse block - relay 53 terminal 87 and AFPCM X1 pin H.

• If the resistance is greater than the specified value, test the affected circuit for an open/high resistance.

10. Using the PU probe J 35616-4A, test for greater than 1M ohm between the transmission pump switch control circuit, AFPCM X1 pin H and a good ground.

• If the resistance is less than the specified value, test the affected circuit for an short to ground.

11. Using the PU probe J 35616-4A, test for 0.0 V between the transmission pump switch control circuit, AFPCM X1 pin H and a good ground.

• If the voltage is greater than the specified value, test the affected circuit for an short to voltage.

12. Key OFF.
13. Install the Trans Pump MTR Relay.
14. Key ON. Engine OFF.
15. Using the PU probe J 35616-4A and a fused jumper wire, test for B+ (+0.0/-1.0 V) between the following circuits and the positive terminal of the battery:

* Transmission pump driver error circuit, AFPCM X1 pin A
* Hybrid control module pump control circuit, AFPCM X1 pin B
* Ground circuit, AFPCM X1 pin E

• If the voltage is less than the specified value, test the affected circuit for an open/high resistance, short to ground or short to voltage. If all circuits and connections test normal, replace the AFPCM.

16. Using the PU probe J 35616-4A and a fused jumper wire, test for 12-13 V between the Traction Control Switch Signal circuit, AFPCM X1 pin C, and the negative terminal of the battery.

• If the voltage is less than the specified value, test the affected circuit for an open/high resistance, short to ground or short to voltage. If all circuits and connections test normal, replace the AFPCM.

17. Using the PU probes J 35616-4A, test for 0.5-3.0 ohm between the transmission pump high reference circuit, AFPCM X1 pin G and the transmission pump low reference circuit, AFPCM X1 pin F.

• If the resistance is greater than the specified range, test the affected circuits for an open/high resistance. If all circuits and connections test normal, test the automatic transmission auxiliary fluid pump.
• If the resistance is less than the specified range, test the affected circuits for an short together condition. If all circuits and connections test normal, test the automatic transmission auxiliary fluid pump.

18. If all circuits and connections test normal, replace SGCM assembly including the AFPCM module.

Component Testing

Relay Test
1. Ignition OFF, disconnect the Auxiliary Trans Pump Relay.
2. Using the PU probes J 35616-5, test for 72-82 ohm of resistance between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

• If not the specified value, replace the relay.

4. Using the PU probes J 35616-5, connect the 9 V power source EL-49741 harness between relay terminal 85 and 86. You should be able to hear the relay activate. Test for less than 2 ohm of resistance between terminals 30 and 87.

• If greater than the specified value, replace the relay.

Auxiliary Fluid Pump Test
1. Ignition OFF.
2. Disconnect the X1 connector at the automatic transmission Auxiliary Fluid Pump.
3. Using the PU probe J 35616-4A, connect a jumper wire between the transmission Pump Low Reference, Auxiliary Fluid Pump harness X1 pin B and a good ground.
4. Using the PU probe J 35616-4A, connect a fused jumper wire to the automatic transmission Pump High Reference, Auxiliary Fluid Pump harness X1 pin A.
5. Touch the other end of the fused jumper wire to a 12V source. You should be able to hear the Auxiliary Fluid Pump start running. A stethoscope may be necessary to hear pump running.

• If the Auxiliary Fluid Pump does not start running, test the Auxiliary Fluid Pump pigtail harness for an open/high, short to ground or short together condition. If all circuits and connections test normal, replace the Auxiliary Fluid Pump.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the repair.

* Control Module References (Programming and Relearning) for SGCM or AFPCM replacement, setup, and programming.
* Auxiliary Fluid Pump Replacement (Auxiliary Fluid Pump Replacement)

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