Circuit/System Testing

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Do not replace the fuel pump control module based on a history DTC P2635. The DTC P2635 may be stored but that does not indicate a failure of the fuel pump control module. Refer to Strategy Based Diagnosis for further history DTC diagnostics.

Verify that DTCs P018C, P018D, P0231, P0232, or P023F are not set.
- If the DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
Ignition OFF, disconnect the harness connector at the G12 Fuel Pump.
Ignition OFF, test for less than 5.0 Ω between the G12 Fuel Pump low reference circuit terminal A and ground.
- If greater than the specified range, test the G12 Fuel Pump low reference circuit for a high resistance. If the circuit tests normal, replace the K27 Fuel Pump Control Module.
Ignition OFF, install a test lamp between the control circuit terminal D and the low reference circuit terminal A.
Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K27 Fuel Pump Control Module.
- If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K27 Fuel Pump Control Module.
Perform the Fuel System Diagnosis (Without FPCM) , Fuel System Diagnosis (FPCM) to verify proper fuel pressure.
- If the fuel pressure is not normal, replace the G12 Fuel Pump.
If all circuits test normal, replace the K27 Fuel Pump Control Module.