Faulty Glow Plug Control Module (GPCM)
Glow Plug Control Module harness is open or shorted
Glow Plug Control Module circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
The Glow Plug Control Module (GPCM) has the ability to perform internal diagnostics for the temperature sensor circuit. The GPCM monitors the internal temperature sensor voltage and if the voltage is less than 0.21 V or greater than 4.94 V. The GPCM will send a message to the Engine Control Module (ECM) to set the appropriate Diagnostic Trouble Code (DTC). A DTC is detected when one of the GPCM temperature sensors voltage falls outside the calibrated threshold for greater than 1.3 s.