Glow Plug Monitor (GPM)
The 6.0L diesel engine uses a GPM system designed to detect failed glow plugs or failed wiring in the glow plug system. DTCs indicate which cylinder has failed glow plugs or failed glow plug wiring.
The glow plug system is composed of a solid state glow plug control module (GPCM), glow plugs, and the associated wiring harness. The glow plug on-time is controlled by the PCM and is a function of oil temperature, barometric pressure, and battery voltage. The PCM enables the GPCM which powers the individual glow plugs. Glow plug on-time varies between 1 to 120 seconds. In addition to the PCM control, the GPCM limits the glow plug operation to 180 seconds regardless of the PCM commanded on-time. The power to the glow plugs is provided through the GPCM solid state drivers directly from the vehicle battery. The GPCM monitors and detects individual glow plug functionality, and the control and communication links to the PCM. The failures detected by the GPCM are passed to the PCM using a serial communication signal on the diagnostic line.
The key on engine off (KOEO) test is carried out in order to test the GPCM control circuit for failure. The glow plugs are not operated during this test.
The glow plug monitor self-test is a functional KOER test of the PCM carried out on demand with the engine running and the A/C off. The PCM activates the GPCM which monitors the glow plugs. The accelerator pedal may be used to increase the engine speed to increase voltage if needed. A fault must be present at the time of testing for the test to detect a fault. The DTCs are sent to the PCM on the diagnostic line and output to the diagnostic tool.
The following is an example of some of the input and output components monitored by the PCM. The components monitored belong to the engine system.
- Inputs:
engine oil temperature (EOT), barometric pressure sensor (BARO)
- Outputs:
GPCM
- The MIL is activated after a fault if the fault detected affects emissions.