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Home >> GMC >> 1987 >> Forward Control 7.4 W, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 24 (Engine Controls - Tests W/Codes - 6.5L Diesel) >> Diagnostic Trouble Code Charts >> DTC 29 - Glow Plug Relay Circuit Fault >> Function

DTC 29 - Glow Plug Relay Circuit Fault: Function

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Vandura Special, 1994 GMC Vandura, 1994 GMC Rally Camper Special, 1994 GMC Rally, and 1994 GMC Forward Control. However, it is still accessible from the selected car via links, so may be relevant.

The glow plug system is used to assist in providing the heat required to begin combustion during engine starting at cold ambient temperatures. The glow plugs are heated before and during cranking, as well as initial engine operation. The PCM controls the glow plugs by sending a battery voltage signal. PCM will default to hard start. DTC 29 will set when:

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