Known Issues - FPCM System

While the FPCM has the capability of detecting failure modes, the faults are not always reported out as intended. Some vehicles have incorrect calibrations that will read the FPCM messages incorrectly and set the DTCs incorrectly. On these vehicles it is best not to rely on the DTC, or DTC Description when deciding which portion of the system to diagnose. In these cases it is best to read and understand how the system operates, then diagnose the entire system to determine where the failure lies by performing the Complete Fuel Pump Control Module System Diagnostics (Not DTC Specific)  procedure. This diagnostic can also be used to diagnose the FPCM command, feedback and fuel pump control circuits on vehicles with the correct calibration software since to tests the overall operation of the system.

The vehicles listed below will set faults incorrectly for the model years listed and should always be diagnosed using the Not DTC specific system approach.

• DS - model years 2016-2019
• RU - model years 2017-2018
• JL - model year 2018
• JT - model year 2020

The exceptions to the information above are the Loss of Communication, Fuel Rail Pressure Sensor and Fuel Pump Relay Control circuit faults. These faults should typically set correctly since they are detected by the PCM directly, not the FPCM.

Some of the DTCs have changed on vehicles equipped with the 3.0L GMET6 engines.

• The DTCs P025A (FPCM 1) and P027A (FPCM 2) have been used for detecting a missing or invalid command signal from the PCM to the FPCM. These DTC have been split.
  • For FPCM 1, P025A will set for an invalid command signal. P023F will now set for a missing command signal.
  • For FPCM 2, P027A will set for an invalid command signal. P2632 will now set for a missing command signal.
• The P062A DTC that was used for fuel system pressure out of range has been replaced with DTC P2635.