Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

DTC P0671-P0678

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics
1	Did you perform the Diagnostic System Check - Engine Controls?	-	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Is DTC P0670 set?	-	Go to DTC P0670	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition. Turn ON the ignition, with the engine OFF. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records. Did the DTC fail this ignition?	-	Go to Step 4	Go to Intermittent Conditions
4	Turn ON the ignition, with the engine OFF. Probe the terminal on the affected glow plug, with an unpowered test lamp connected to the ground. IMPORTANT: The glow plugs can only be commanded ON once per ignition cycle. Turn the ignition OFF and ON to command the glow plugs ON each time with a scan tool. Command the glow plugs ON, with a scan tool. Does the test lamp illuminate with the glow plugs commanded ON?	-	Go to Step 5	Go to Step 6
5	Turn OFF the ignition. Disconnect the glow plug connector at the affected glow plugs. Probe the terminal on the glow plug with an unpowered test lamp connected to battery voltage. Does the glow plug illuminate the test lamp?	-	Go to Step 8	Go to Step 11
6	Test the affected glow plug harness between the glow plug controller and the glow plug for the following conditions: An open A short to ground A short to voltage Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 7
7	Test for an intermittent and for a poor connection at the harness connector of the glow plug controller. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 12
8	IMPORTANT: The DMM and test leads must be calibrated to 0 ohms in order to prevent misdiagnosis. Use the DMM to perform this test. Refer to the DMM User Manual for calibration procedure. Measure the resistance between the affected glow plug terminal of the glow plug and a good ground on the engine with a DMM.Does the DMM display a resistance below the specified value?	1 ohm	Go to Step 9	Go to Step 11
9	IMPORTANT: The DMM and test leads must be calibrated to 0 ohms in order to prevent misdiagnosis. Use the DMM to perform this test. Refer to the DMM User Manual for calibration procedure. Disconnect the glow plug controller harness connector. Measure the resistance from the affected glow plug supply voltage circuit between the glow plug harness connector and the glow plug controller harness connector with a DMM. Does the DMM display a resistance below the specified value?	1 ohm	Go to Step 12	Go to Step 10
10	Repair or replace the glow plug harness. Refer to Wiring Repairs in Wiring Systems. Is the action complete?	-	Go to Step 13	-
11	Replace the glow plug. Refer to Glow Plug Replacement - Bank 1 or Glow Plug Replacement - Bank 2 . Did you complete the replacement?	-	Go to Step 13	-
12	Replace the glow plug controller. Refer to Glow Plug Controller Replacement . Did you complete the replacement?	-	Go to Step 13	-
13	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records. Did the DTC fail this ignition?	-	Go to Step 2	Go to Step 14
14	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List	System OK