P0674

DTC P0671 - P0674

CIRCUIT DESCRIPTION
The glow control system is operated when the engine coolant temperature is low, which allows easier engine starting. If the ignition switch is turned ON when the engine coolant temperature is low, the engine control module (ECM) illuminates the glow indicator lamp and turns ON the glow plugs via the glow plug controller. After a fixed time passes, the ECM turns OFF the glow indicator lamp and the glow plugs via the glow plug controller. The glow plug controller has the ability to perform internal checks, an open or a short circuit on each of the glow plug circuits. If the glow plug controller senses a problem in a glow pug circuit, the glow plug on the affected cylinder will be disabled and the glow plug controller will send an error message to the ECM via the controller area network (CAN) communication bus. DTC P0671 - P0674 will set depending upon which cylinder failed. This DTC will only run once per ignition cycle within the enabling condition.

Condition for Running the DTC
- DTCs U0073 and U0106 are not set.
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.

Condition for Setting the DTC
- The glow plug controller detects an open or a short circuit in the glow plug circuit.

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records

Condition for Clearing the MIL/DTC
- The ECM turns OFF the MIL after 3 consecutive driving cycles when 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 after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
If an intermittent condition is suspected, the following may cause an intermittent:
- Faulty glow plug(s)
- Poor connections
- Misrouted harness
- Rubbed through wire insulation
- Broken wire inside the insulation

Check for the following conditions:
- Poor connection at glow plug controller: Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness: Inspect the wiring harness for damage. If the harness appears to be OK, observe the "DTC P0671 - P0674 Last Test" display on the scan tool with engine running while moving connectors and wiring harness. A change in the display will indicate the location of the fault.

NOTE: Each Diagnostic Trouble Code (DTC) agrees with the engine cylinder order.
P0671: Cylinder No. 1
P0672: Cylinder No. 2
P0673: Cylinder No. 3
P0674: Cylinder No. 4

DTC P0671 - P0674
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views

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