Refer to
DIESEL PCM, GLOW PLUGS, FUSE-RELAY
Circuit Description
The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. The glow plugs are heated before and during cranking, as well as initial engine operation. The PCM controls the glow plug ON times by monitoring coolant temperatures and glow plug voltage.
Conditions for Running the DTC
The ignition switch in the ON position.
Conditions for Setting the DTC
| • | The PCM has commanded glow plugs ON and the glow plug signal voltage is less than 4.0 volts. |
| or |
| • | The PCM has commanded glow plugs OFF and the glow plug signal voltage is greater than 4.0 volts. |
| or |
| • | When the PCM has commanded glow plugs ON and there is more than a 2 volt difference between glow plug voltage and ignition voltage. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records will store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after three consecutive trips without a fault condition. |
| • | A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures |
| • | The use of a scan tool. |
Diagnostic Aids
If glow plug relay is stuck in the ON position, check for proper operation of glow plugs, refer to Glow Plug System Check . When glow plugs are commanded ON by the Scan tool, an internal PCM timer protects the glow plugs from damage by cycling them ON for 3 seconds and the OFF for 12 seconds.
The glow plug output feed wire nut and battery feed wire nut at the relay should be checked for proper torque (5 N·m 44 lb in) and for corrosion.
An intermittent may be caused by the following:
| • | Poor connections. |
| • | Rubbed through wire insulation. |
| • | Broken wire inside the insulation. |
Test Description
The number(s) below refer to the Step number(s) on the Diagnostic Table.
-
This step will determine if P0380 is a hard failure.
-
This step will determine if the PCM is requesting the glow plug system ON.
-
This step will determine if the glow plug relay has been activated and the output voltage has been seen by the PCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing any DTCs, use the scan tool Capture Info to save freeze frame and failure records for reference, as the Scan tool loses data when using the Clear Info function. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Does the Scan Tool display the Glow Plug System as enabled? | -- | |||
Does the Scan Tool display the Glow Plugs at the specified value? | B+ | |||
4 | Does the Scan Tool display Glow Plug voltage present all the time? | -- | ||
5 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids If any additional DTCs were stored, refer to those table(s). Were there any additional DTCs stored? | -- | Go to the Applicable DTC Table | Go to Diagnostic Aids |
6 |
Is the test light ON? | -- | ||
7 |
Is the test light ON? | -- | ||
8 |
Is the voltage at the specified value? | B+ | ||
9 |
Is the test light ON? | -- | ||
Is the test light ON when the Scan Tool commands the glow plugs ON? | -- | |||
11 | Repair an open or a short to ground in glow plug relay ignition feed circuit. Is the action complete? | -- | -- | |
12 | Repair any open or poor connections in the glow plug relay ground circuit. Is the action complete? | -- | -- | |
13 |
Was a problem found? | -- | ||
14 | Check the glow plug relay control circuit for a proper connection at the PCM and replace the terminal if necessary. Was a problem found? | -- | ||
15 |
Was a problem found? | -- | ||
16 | Check the glow plug relay signal circuit for a proper connection at the PCM and replace the terminal if necessary. Was a problem found? | -- | ||
17 |
Is the test light ON all the time? | -- | ||
18 | Repair the short to voltage on the glow plug relay control circuit. Is the action complete? | -- | -- | |
19 | Replace the glow plug relay. Refer to Glow Plug Relay Replacement . Is the action complete? | -- | -- | |
20 | Repair an open or a short to ground in the battery positive feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
21 | Replace the PCM. Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
22 |
Does the Scan tool indicate the diagnostic Passed? | -- | ||
23 | Does the Scan tool display any additional undiagnosed DTCs? | -- | Go to the Applicable DTC Table | System OK |
