6.2L & 6.5L GM Diesel Glow Plug Controller

How to Replace the Glow Plug Controller on a 6.2L or 6.5L Detroit Diesel

The glow plug controller on a 6.2L/6.5L diesel is nothing more than a relay that is energized in order to activate the glow plug preheat sequence. The glow plug system is cycled when the key is switched to the "run" position and the wait-to-start (WTS) light will be illuminated during this time. A post-heat cycle will be initiated under certain conditions, at which point the glow plugs will be cycled in short 1 to 2 second bursts while the engine is running.

Applicable model years: 1985+ 6.2L & 6.5L GM/Detroit diesel engines
1985 - 1993 6.5L diesel glow plug controller: Airtex 1R1332
1994+ 6.5L diesel glow plug controller: Airtex 1R1372

Glow plug cycle time is dependent on engine coolant temperature. On pre-1994 model engines, a glow plug inhibit switch disables the glow plug system if the coolant temperature exceeds 125 °F. On 1994 and newer engines, the ECM will initiate the glow plugs for a predetermined period of time based on engine coolant temperature. The WTS light will be illuminated anytime the glow plug system is activated, including during any post-heat cycles. The glow plug controller for all 1992 - 1993 engines and 1994+ non-electronic (fully mechanical injection pump, no electronic pump mounted driver) engines uses a 4 pin connector. All 1994+ engines with an electronic injection system (electronic pump mounted driver) use a 3 pin glow plug controller. You can verify your controller type by simply pulling the electrical connector off and counting the male pins. The following procedures are applicable to all 1985+ 6.2L and 6.5L GM diesels. For a complete list of glow plug system diagnostics and troubleshooting strategies, see: 6.2L & 6.5L GM diesel glow plug system troubleshooting.

The following procedures are based on a 6.5L turbocharged engine. The steps are identical for 6.2L and naturally aspirated 6.5L engines, however there are subtle differences (such as the absence of a wastegate solenoid).

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glow plug controller location, 6.2 and 6.5 GM/Detroit diesel

• Disconnect both negative battery cables.

• Remove the plastic "Turbo Power" engine cover (if applicable).

• Locate the glow plug controller on the driver side, rear of the engine. It is mounted to the right of and behind the fuel filter housing on a bracket near the firewall.

glow plug controller terminals

• Remove the positive input and output terminals with a 13 mm socket.

• The glow plug controller studs are shared with the wastegate solenoid. Remove the nuts from both glow plug controller studs and the third nut holding down the wastegate solenoid bracket. A 15 mm socket is required.

• Gently remove the wastegate solenoid bracket from the mounting studs and push it aside without putting any strain on the lines/harness.

glow plug controller removal

• Lift the glow plug controller off of the mounting studs and carefully rotate it until the connector release is accessible. Do not put any strain on the connector wires/harness.

• Pull the blue safety/retaining clip from the connector (if applicable), then release and remove the connector from the glow plug controller.

3 pin 6.5 diesel glow plug controller

• Install the glow plug controller in reverse. Use dielectric grease on the connector pins and input/output lugs.

• Reconnect the negative battery cables and test for proper glow plug operation.