Circuit Description
The glow plug controller has the ability to perform internal checks, an open or a short to ground on each of the glow plug circuits. If the glow plug controller senses a problem in a glow plug circuit, the glow plug on the affected cylinder will be disabled and the glow plug controller will send an error message to the engine control module (ECM). If this condition exists, the DTC will set.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC P0671 Glow Plug 1 Control Circuit |
| • | DTC P0672 Glow Plug 2 Control Circuit |
| • | DTC P0673 Glow Plug 3 Control Circuit |
| • | DTC P0674 Glow Plug 4 Control Circuit |
| • | DTC P0675 Glow Plug 5 Control Circuit |
| • | DTC P0676 Glow Plug 6 Control Circuit |
| • | DTC P0677 Glow Plug 7 Control Circuit |
| • | DTC P0678 Glow Plug 8 Control Circuit |
Conditions for Running the DTC
| • | DTC U0073 or U0106 are not set. |
| • | The ignition is ON. |
| • | DTC P0671-P0678 runs continuously. |
Conditions for Setting the DTC
The glow plug controller detects an open or a short to ground in the glow plug circuit for less than 1 second.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | 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. |
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||||
2 | Is DTC P0670 set? | -- | Go to DTC P0670 | Go to Step 3 | ||||||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||||||||
4 |
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. Does the test lamp illuminate with the glow plugs commanded ON? | -- | Go to Step 5 | Go to Step 6 | ||||||||||||
5 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 11 | ||||||||||||
6 |
Important:
Test the affected glow plug harness between the glow plug controller and the glow plug for the following conditions:
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 ohms | 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.
Does the DMM display a resistance below the specified value? | 1 ohms | 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 |
Important: If a glow plug is replaced and the tip is missing or burned off, the cylinder head must be removed and all debris must be cleaned out of the cylinder. 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 Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||||
13 |
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 - Vehicle in Vehicle DTC Information | System OK | ||||||||||||
