Test Procedure
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- AF1 PRELIMINARY DIAGNOSIS
- Key OFF.
- Carry out a visual inspection.
- Key ON, engine OFF.
- Record the freeze frame data.
- Carry out the KOER Glow Plug Monitor self-test.
Is DTC P0670, P0671, P0672, P0673, P0674, P0675, P0676, P0677, P0678, or P0683 present?
Yes No NOTE: IF DTC P0670 and P0683 are present, carry out DTC P0670 diagnosis before diagnosing DTC P0683.For DTC P0671, P0672, P0673, P0674, P0675, P0676, P0677, or P0678GO to AF2.For DTC P0670, GO to AF8.For DTC P0683, GO to AF16.UNABLE to duplicate the condition. CHECK for a loose connection, and damaged or corroded terminals. WIGGLE the harness attempting to recreate the fault. REPAIR as necessary. REFER to SYMPTOM CHARTS - 6.0L DIESEL if a driveability concern exists. - AF2 DIAGNOSTIC TROUBLE CODES P0671, P0672, P0673, P0674, P0675, P0676, P0677, OR P0678 NOTE: Refer to wiring diagram, Figure at the beginning of this pinpoint test.NOTE: Glow plugs are numbered front to rear with even numbers on left side of the engine.NOTE: Use the wiring diagram to match the connector pins with the DTCs.
- Possible causes:
- glow plug circuit open
- glow plug circuit shorted
- GPCM
- glow plug
- Key OFF.
- Disconnect the suspect glow plug bus bar.
- Check for loose, damaged, or backed out terminals.
- Measure the resistance between the suspect glow plug bus bar pin, component side and ground.
Is the resistance between 0.5 and 2 ohms?
Yes No GO to AF4. GO to AF3. - Possible causes:
- AF3 CHECK THE GLOW PLUG CIRCUIT BETWEEN THE BUS BAR CONNECTOR AND THE GLOW PLUG
- Disconnect the bus bar harness from the glow plugs.
- Measure the resistance between the suspect glow plug bus bar pin, harness side and the suspect glow plug pin, harness side.
Is the resistance less than 5 ohms?
Yes No INSTALL a new glow plug. CLEAR the DTCs. REPEAT the self-test. INSTALL a new bus bar. CLEAR the DTCs. REPEAT the self-test. - AF4 CHECK THE GLOW PLUG VOLTAGE
- Disconnect the suspect GPCM connector.
- Key ON, engine OFF.
- Measure the voltage between the GPCM connector VBATT circuit pin 3, harness side and ground.
Is the voltage greater than 10 volts?
Yes No GO to AF5. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - AF5 CHECK THE GLOW PLUG CIRCUIT FOR AN OPEN
- Key OFF.
- Measure the resistance between the suspect glow plug GPCM connector pin, harness side and the glow plug bus bar pin, harness side.
Is the resistance less than 5 ohms?
Yes No GO to AF6. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - AF6 CHECK THE GLOW PLUG CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between the suspect glow plug GPCM connector pin, harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes No GO to AF7. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - AF7 CHECK THE GLOW PLUG CIRCUIT FOR A SHORT TO VOLTAGE
- Key ON, engine OFF.
- Measure the voltage between the suspect glow plug GPCM connector pin, harness side and ground.
Is any voltage indicated?
Yes No REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. INSTALL a new GPCM. CLEAR the DTCs. REPEAT the self-test. - AF8 DIAGNOSTIC TROUBLE CODE P0670 NOTE: Refer to Figure for PCM and component connector pin numbers at the beginning of this pinpoint test.
- Possible causes:
- control line open
- control line shorted to ground or power
- PCM
- GPCM
- Key OFF.
- Disconnect the PCM.
- Disconnect the GPCM (green connector).
- Measure the resistance between the green GPCM connector pin 8, harness side and the PCM engine harness connector pin 3, harness side.
Is the resistance less than 5 ohms?
Yes No GO to AF9. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - Possible causes:
- AF9 CHECK THE CONTROL CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between the green GPCM connector pin 8, harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes No GO to AF10. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - AF10 CHECK THE CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
- Key ON, engine OFF.
- Measure the voltage between the green GPCM connector pin 8, harness side and ground.
Is any voltage indicated?
Yes No REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. GO to AF12. - AF12 CHECK THE GPCM FOR VOLTAGE
- Key OFF.
- Disconnect the GPCM (black connector).
- Key ON, engine OFF.
- Measure the voltage between the black GPCM connector pin 9, harness side and ground.
Is the voltage greater than 10 volts?
Yes No GO to AF13. REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test. - AF13 CHECK THE GPCM CONTROL CIRCUIT NOTE: With the key ON, engine OFF the PCM provides a path to ground for the glow plug control circuit.
- Key OFF.
- Connect the GPCM (black connector).
- Connect the PCM.
- Measure the voltage between the positive battery terminal and the green GPCM connector pin 8, harness side.
- Key ON, engine OFF.
Is the voltage greater than 10 volts?
Yes No INSTALL a new GPCM. CLEAR the DTCs. REPEAT the self-test. INSTALL a new PCM. CLEAR the DTCs. REPEAT the self-test. - AF16 DIAGNOSTIC TROUBLE CODE P0683 NOTE: Refer to Figure for PCM and component connector pin numbers at the beginning of this pinpoint test.
- Possible causes:
- diagnostic line open
- diagnostic line shorted to ground
- diagnostic line shorted to power
- PCM
- GPCM
- Key OFF.
- Disconnect the PCM.
- Disconnect the GPCM (green connector).
- Measure the resistance between the green GPCM connector pin 9, harness side and the PCM engine harness connector pin 17, harness side.
Is the resistance less than 5 ohms?
Yes No GO to AF17. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - Possible causes:
- AF17 CHECK THE DIAGNOSTIC CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between the green GPCM connector pin 9, harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes No GO to AF18. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - AF18 CHECK THE DIAGNOSTIC CIRCUIT FOR A SHORT TO VOLTAGE
- Key ON, engine OFF.
- Measure the voltage between the green GPCM connector pin 9, harness side and ground.
Is any voltage indicated?
Yes No REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. GO to AF19. - AF19 CHECK THE GPCM FOR VOLTAGE
- Key OFF.
- Disconnect the GPCM (black connector).
- Key ON, engine OFF.
- Measure the voltage between black GPCM connector pin 9, harness side and ground.
Is the voltage greater than 10 volts?
Yes No GO to AF20. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. - AF20 CHECK THE GPCM OPERATION
- Key OFF.
- Connect the GPCM.
- Connect a 10-amp fused jumper wire between the PCM engine connector pin 3, harness side and ground.
- Key ON, engine OFF.
- Measure the voltage between the PCM engine harness connector pin 17, harness side and ground.
Is the voltage between 5 and 12 volts?
Yes No INSTALL a new PCM. CLEAR the DTCs. REPEAT the self-test. INSTALL a new GPCM. CLEAR the DTCs. REPEAT the self-test.