System Check - Glow Plugs

Glow Plug System Check:

Circuit Description
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. A DTC 29 will be set when the glow plug relay output is found to have a fault. This can be found by comparing glow plug volts to system voltage.

Chart Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if the glow plugs are faulty or if the problem lies in the wiring portion of the circuit.
2. If the relay contacts are shorted together, there will be 12 volts supplied to the glow plugs at all times. Since these are 6 volt glow plugs, they will be damaged by the constant high voltage.