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For 1990-2009 cars only

DTC P0380 Californiaand RPO NF4, VCL

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 Engine Control Module (ECM) controls the glow plug ON times by monitoring coolant temperature and glow plug voltage. The California Glow Plug system has eight individual glow pllug supply circuits between the controller and the glow plugs. If the feedback voltage from the controller to the ECM is not within range, DTC P0380 will set.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

    • The glow plugs are commanded OFF and the glow plug feedback is more than 2.0 volts.
        or
    • The glow plugs are commanded on and the glow plug feedback is not between 5.0 volts and 6.2 volts.

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.

Diagnostic Aids

Important:  If the glow plug relay is stuck in the ON position, check for proper operation of the glow plugs. When the glow plugs are commanded ON by the scan tool, an internal engine control module (ECM) timer protects the glow plugs from damage by cycling them ON for 3 seconds and the OFF for 12 seconds. The glow plug relay battery feed wire nut at the relay should be tested for proper torque. The California glow plug system will send the following voltages, or signals to the ECM:

Signal Voltage

Glow Plugs Failed Open

5.00-6.00

None

2.00-3.00

1

1.00-2.00

2

0.80-1.70

3

Less than 1.3

4 or more

An intermittent may be caused by the following:

    • Poor connections (terminal tension)
    • Rubbed-through wire insulation
    • Broken wire inside the insulation
    • A short to battery positive voltage on the glow plug relay control circuit

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step will determine if diagnostic trouble code (DTC) P0380 is a hard failure.

  2. This step will determine if there is a short to voltage on the signal circuit.

  3. This step will determine if there is ignition voltage at the glow plug relay.

  4. This step will determine if the glow plug control circuit and ECM are working properly.

  5. This step will determine if there is a short to voltage on the relay control circuit.

  6. This step will determine if the glow plugs or the glow plug harness is causing the DTC P0380.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

--

2

Important : If this DTC set after an ECM reflash.

  1. Connect a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the Glow Plug System Type parameter on the scan tool.

Does the scan tool display the Glow Plug System Type as California?

--

Go to Step 3

Go to DTC P0380

3

  1. Connect a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to command the glow plugs ON and OFF.
  4. Observe the glow plug feedback parameter on the scan tool.

Does the scan tool display the glow plug feedback voltage parameter is within the specified range?

5.0-5.6 V

Go to Step 7

Go to Step 4

4

Does the scan tool display a glow plug feedback voltage parameter more than the specified value?

5.6 V

Go to Step 20

Go to Step 5

5

Does the scan tool display a glow plug feedback voltage parameter more than the specified value?

0.45 V

Go to Step 10

Go to Step 6

6

  1. Turn ON the ignition, with the engine OFF.
  2. Touch the battery feed stud on the glow plug relay with an unpowered test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 23

7

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If any additional DTCs were stored, refer to those tables.

Were there any additional DTCs stored?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Diagnostic Aids

8

  1. Disconnect the glow plug relay middle connector.
  2. Turn ON the ignition, with the engine OFF.
  3. With an unpowered test lamp connected to ground, probe the glow plug relay harness ignition feed circuit.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 15

9

  1. Turn ON the ignition, with the engine OFF.
  2. Connect an unpowered test lamp to B+, probe the glow plug relay harness ground circuit.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 16

10

  1. Turn ON the ignition, with the engine OFF.
  2. Verify that the glow plug relay harness is disconnected.
  3. With an unpowered test lamp connected to ground, probe the glow plug relay control circuit at the glow plug relay harness connector.
  4. Use a scan tool in order to command the glow plugs ON and OFF.

Does the test lamp illuminate with the scan tool command ON?

--

Go to Step 12

Go to Step 11

11

Does the test lamp illuminate all of the time?

--

Go to Step 22

Go to Step 17

12

  1. Verify that the glow plug relay is still disconnected.
  2. Turn ON the ignition, with the engine OFF.
  3. Using the J 35616 Connector Test Adapter Kit, jumper the glow plug control circuit to the glow plug signal circuit scan tool.
  4. Use a scan tool in order to command the glow plugs ON.
  5. Observe the scan tool while the glow plugs are commanded ON.

Does the glow plug parameter voltage measure near the specified value?

Battery Voltage

Go to Step 13

Go to Step 19

13

  1. Turn OFF the ignition.
  2. Disconnect the right and left bank glow plug output circuit connectors at the glow plug relay.
  3. With an unpowered test lamp connected to B+, probe each circuit.

Does the test lamp illuminate for each circuit?

--

Go to Step 25

Go to Step 14

14

  1. Turn OFF the ignition.
  2. Disconnect each glow plug connector at the glow plug that did not illuminate the test lamp.
  3. With an unpowered test lamp connected to B+, probe the terminal on the glow plug.

Does each glow plug illuminate the test lamp?

--

Go to Step 25

Go to Step 24

15

Repair an open or a short to ground in the glow plug relay ignition 1 voltage circuit.

Did you complete the repair?

--

Go to Step 28

--

16

Repair the open circuit or poor connections in the glow plug relay harness ground circuit.

Did you complete the repair?

--

Go to Step 28

--

17

Inspect the glow plug relay control circuit for an open or short to ground and repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 28

Go to Step 18

18

Inspect the glow plug relay control circuit for a proper connection at the ECM and replace the terminal if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 28

Go to Step 27

19

Inspect the glow plug relay signal circuit for an open or short to ground and repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 28

Go to Step 26

20

Inspect the glow plug relay signal circuit for a proper connection at the ECM and replace the terminal if necessary.

Did you find an improper connection and make the necessary replacement?

--

Go to Step 28

Go to Step 21

21

Inspect for a short to voltage in the glow plug relay signal circuit and repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find the improper condition?

--

Go to Step 28

Go to Step 25

22

Inspect for a short to voltage in the glow plug control circuit and repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find the improper condition?

--

Go to Step 28

Go to Step 27

23

Repair the open or poor connection on the battery voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 28

--

24

Replace any glow plug that did not illuminate the test lamp.

Did you complete the replacement?

--

Go to Step 28

--

25

Inspect for an open or poor connection in the glow plug harness. Refer to Wiring Repairs in Wiring Systems.

Did you find and correction the condition?

--

Go to Step 28

Go to Step 26

26

Replace the glow plug relay. Refer to Glow Plug Relay Replacement .

Did you complete the replacement?

--

Go to Step 28

--

27

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 28

--

28

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 29

Go to Step 2

29

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK

DTC P0380 Federal RPO FE9, NG1

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 engine control module (ECM) controls the glow plug ON times by monitoring coolant temperature and glow plug voltage.

Conditions for Running the DTC

The ignition switch in the ON position.

Conditions for Setting the DTC

    • The ECM has commanded glow plugs ON and the glow plug signal voltage is less than 4 volts.
        or
    • The ECM has commanded glow plugs OFF and the glow plug signal voltage is more than 4 volts.

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.

Diagnostic Aids

If the glow plug relay is stuck in the ON position, check for proper operation of the glow plugs, refer to Glow Plug System Diagnosis . When glow plugs are commanded ON by the scan tool, an internal ECM timer protects the glow plugs from damage by cycling them ON for 3 seconds and then 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 numbers below refer to the step numbers on the diagnostic table.

  1. This step will determine if DTC P0380 is a hard failure.

  2. This step determines if there is a relay control circuit or ECM fault that will not energize the relay.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Confirm that the glow plugs are commanded OFF with the scan tool.

Does the scan tool display glow plug feedback signal voltage present all the time?

--

Go to Step 9

Go to Step 3

3

Important: The DMM may indicate a bias voltage on the circuit before the relay is energized. This is normal.

  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the glow plug relay.
  3. Probe the glow plug relay control circuit at the glow plug relay harness connector with a DMM connected to ground. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
  4. Command the glow plug relay ON with a scan tool.

Does the voltage measure near the specified value when the relay is commanded ON?

B+

Go to Step 4

Go to Step 8

4

  1. Turn ON the ignition, with the engine OFF.
  2. Probe the battery positive voltage circuit of the glow plug relay with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 12

5

Probe the ground circuit of the glow plug relay with a test lamp connected to battery voltage. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 13

6

  1. Reconnect the glow plug relay.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the glow plug signal circuit at the glow plug relay connector with a test lamp connected to a good ground.
  4. Command the glow plug relay ON and OFF with a scan tool.

Does the test lamp illuminate when the scan tool commands the glow plugs ON?

--

Go to Step 7

Go to Step 17

7

  1. Turn OFF the ignition.
  2. Disconnect the ECM. Refer to Engine Control Module Replacement .
  3. Test the glow plug signal circuit for an open or short to ground.

Did you find a problem?

--

Go to Step 14

Go to Step 18

8

  1. Test the glow plug relay control circuit for an open or short to ground.
  2. If the glow plug relay control circuit is open or shorted to ground, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

9

  1. Disconnect the glow plug relay connector. Refer to Glow Plug Relay Replacement .
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the glow plug relay control circuit with a test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate all of the time?

--

Go to Step 10

Go to Step 11

10

  1. Turn OFF the ignition.
  2. Disconnect the ECM. Refer to Engine Control Module Replacement .
  3. Turn ON the ignition.
  4. Probe the glow plug relay control circuit with a test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 16

Go to Step 20

11

Probe the glow plug signal circuit at the harness connector with a test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 15

Go to Step 19

12

Repair the open or short to ground in the battery positive voltage circuit to the glow plug relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

13

Repair the open in the glow plug relay ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

14

Repair the open or short to ground in the glow plug signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

15

Repair the short to voltage in the glow plug signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

16

Repair the short to voltage in glow plug relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

17

  1. Check for poor connections at the glow plug relay. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 19

18

  1. Check for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 20

19

Replace the glow plug relay. Refer to Glow Plug Relay Replacement .

Did you complete the replacement?

--

Go to Step 21

--

20

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 21

--

21

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 22

Go to Step 1

22

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK