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 auxiliary pump relay control circuit sending power to the Hybrid pump driver (HPD). The SGCM monitors all of the circuits of the auxiliary transmission fluid pump control circuits.

The Hybrid Wake Up signal is ON.

P0B09

P2796

SGCM detects an open or short to ground in any circuit of the auxiliary transmission fluid pump control circuit.

DTCs P0B09 and P2796 are Type B DTCs.

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

Schematic Reference

Connector End View Reference

Component Connector End Views

Description and Operation

Starter/Generator Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the transmission fluid pump relay ON and OFF with a scan tool. Listen for the auxiliary transmission fluid pump running and that the trans pump relay clicks. A stethoscope may be necessary to hear pump running.

1. Ignition OFF, disconnect the Auxiliary Transmission Fluid Pump Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the relay switch supply circuit and ground.

⇒	If the test lamp illuminates, test the relay controlled output circuit for a short to voltage.

3. Verify that a test lamp illuminates between the relay coil B+ circuit and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

⇒	If the circuit tests normal and the B+ circuit fuse is open, test the relay coil control circuit for a short to ground. If the circuit tests normal, test or replace the Auxiliary Transmission Pump Relay.

4. Verify that a test lamp illuminates between the relay switch B+ circuit and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

5. Disconnect the harness connector at the Hybrid Pump Driver (HPD).
6. Test for less than 10 ohm of resistance between the HPD ground circuit terminal E and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

7. Test for less than 10 ohm of resistance at bare ground cable attached to Starter Generator Control Module and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

8. Ignition OFF, disconnect the Auxiliary Trans Pump Relay. Test for 72-82 ohms of resistance between terminals 85 and 86.

⇒	If not within the specified range, replace the relay.

9. 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.

10. Install a 5A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay.

11. Test for less than 10 ohm of resistance between the pump control circuit terminal B and terminal 15 of the SGCM.

⇒	If greater than the specified range, test the pump control circuit for an open/high resistance.

12. Test for less than 10 ohms of resistance between the transmission pump driver error circuit terminal A of the HPD and terminal 14 of the SGCM.

⇒	If greater than the specified range, test the transmission pump driver error circuit for an open/high resistance.

13. Test for less than 10 ohms of resistance between the pump motor voltage circuit terminal C of the HPD and terminal 1 of the SGCM.

⇒	If greater than the specified range, test the transmission pump driver error circuit for an open/high resistance.

14. Disconnect Auxiliary Trans pump connector and test for 0.5-3.0 ohm of resistance between transmission pump high reference circuit terminal A and the transmission pump low reference terminal B.

⇒	If not within the specified range, replace the Auxiliary Trans Pump.

15. Disconnect the HPD connector and test for less than 1 ohm of resistance between the Transmission pump high reference circuit terminal G and terminal A and the transmission pump low reference circuit terminal F and terminal B for an open/high resistance.

⇒	If greater than the specified range, test the transmission pump low and high reference circuits for an open/high resistance.

16. If all circuits test normal, replace SGCM and/or HPD module.

Relay Test

1. Ignition OFF, disconnect the Auxiliary Trans Pump Relay.
2. Test for 72-82 ohms 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. Install a 5A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the repair.