Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Test Procedure
- AJ1 CHECK FOR DTCS
Are DTCs P0685, P068A, P2506, P2507 or P2508 present?
Yes No GO to AJ2 . For symptoms without DTCs, GO to AJ3.
For all others, RETURN to ENGINE CONTROLS - SYMPTOM CHARTS (DIESEL) (SECTION 3) , Symptom Charts for further direction. - AJ2 CHECK THE BATTERY AND CHARGING SYSTEM
- Check the battery and charging system voltages. Refer to the Charging System article, Inspection and Verification.
Are the battery and charging system voltages within specifications?
Yes No GO to AJ3 . REPAIR as necessary. REFER to the Charging System article, Symptom Chart to diagnose the system voltage low or battery is discharged symptom or the system voltage high symptom.
Clear the PCM DTCs. REPEAT the self-test. - AJ3 CHECK THE PCM POWER RELAY
- Carry out the PCM power relay component test. Refer to the OEM Wiring Diagrams Component Testing article for testing procedure.
Did the PCM power relay pass the component test?
Yes No GO to AJ4 . INSTALL a new PCM Power Relay. Clear the PCM DTCs. REPEAT the self-test. - AJ4 CHECK THE B+ CIRCUITS FOR VOLTAGE
- Ignition OFF.
- PCM Power Relay connector disconnected.
- Measure the voltage between:
(+) PCM Power Relay Connector, Harness Side (-) B+ - Pin 2, 3 Ground
Is the voltage greater than 10.5 V?
Yes No GO to AJ5 . REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - AJ5 CHECK THE PCMRC CIRCUIT FOR AN OPEN
- PCM-B connector disconnected.
- Measure the resistance between:
(+) PCM-B Connector, Harness Side (-) PCM Power Relay Connector, Harness Side PCMRC - Pin 38 PCMRC - Pin 1
Is the resistance less than 5 ohms?
Yes No GO to AJ6 . REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - AJ6 CHECK THE PCMRC CIRCUIT FOR A SHORT TO GROUND
Is the resistance greater than 10K ohms?
Yes No GO to AJ7 . REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. - AJ7 CHECK THE PCMRC CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition ON, engine OFF.
- Measure the voltage between:
(+) PCM-B Connector, Harness Side (-) PCMRC - Pin 38 Ground
Is any voltage present?
Yes No REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. GO to AJ8 . - AJ8 CHECK THE ISP-R CIRCUIT FOR VOLTAGE
- Ignition OFF.
- PCM Power Relay connector connected.
- Ignition ON, engine OFF.
- Measure the voltage between:
(+) PCM-B Connector, Harness Side (-) ISP-R - Pin 42 Ground
Is the voltage greater than 10.5 V?
Yes No GO to AJ9 . REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - AJ9 CHECK THE ISP-R CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Measure the voltage between:
(+) PCM-B Connector, Harness Side (-) ISP-R - Pin 42 Ground
Is any voltage present?
Yes No REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. GO to AJ10 . - AJ10 CHECK THE VPWR CIRCUIT FOR AN OPEN
- PCM Power Relay connector disconnected.
- Measure the resistance between:
(+) PCM-B Connector, Harness Side (-) PCM Power Relay Connector, Harness Side VPWR - Pin 67, 68, 69 VPWR - Pin 5
Are the resistances less than 5 ohms?
Yes No GO to AJ11 . REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - AJ11 CHECK THE PWRGND CIRCUITS FOR AN OPEN
- Measure the resistance between:
(+) PCM-B Connector, Harness Side (-) PWRGND - Pin 70, 71, 72, 73, 74 Ground
Are the resistances less than 5 ohms?
Yes No GO to AJ12 . REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - Measure the resistance between:
- AJ12 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Visually inspect for:
- pushed out pins
- corrosion
- Connect all the PCM connectors and make sure they seat correctly.
- Carry out the PCM self-test.
- Verify the concern is still present.
Is the concern still present?
Yes No INSTALL a new PCM.
REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) .The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.