Circuit/System Testing
Monitor the GPCM Data Display Ignition 1 Signal parameter for battery voltage with a scan tool.
- If the Ignition 1 Signal parameter is not battery voltage, test the battery positive voltage circuit to the glow plug control module for an open, or short to ground. If the circuits test normal replace the GPCM.
- If the Ignition 1 Signal parameter is battery voltage, replace the GPCM.