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
- B1 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTCS)
Are DTCs P0686, P0687, P0689, P0690, P2531, P2533 or P2535 present?
Yes No GO to B2. RETURN to SYMPTOM CHARTS for further direction. - B2 CHECK FOR BCM DTCS
- Carry out the BdyCM self-test.
Are any DTCs present?
Yes No REFER to the Service Information, Multifunction Electronic Modules to diagnose the BCM DTCs.
Clear the PCM DTCs. REPEAT the self-test.GO to B3. - B3 CHECK THE KEYST PIDS
- Ignition ON, engine OFF.
- Access the PCM and monitor the KEYST (MODE) PID.
Does the PID indicate ON?
Yes No GO to B6. GO to B4. - B4 CHECK THE ISP-R CIRCUIT
- Ignition OFF.
- PCM connector disconnected.
- Ignition ON, engine OFF.
- Measure the voltage between:
(+) PCM Connector, Harness Side (-) ISP-R - Pin B8 Ground
Is the voltage greater than 10.5 V?
Yes No GO to B5. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - B5 CHECK THE ISP-R CIRCUIT FOR A SHORT TO VOLTAGE
Is any voltage present?
Yes No REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. GO to B13. - B6 CHECK THE B+ VOLTAGE TO PCM POWER RELAY
- Ignition OFF.
- PCM Power Relay connector disconnected.
- Measure the voltage between:
(+) PCM Power Relay Connector, Harness Side (-) B+ - Pin 1, 3 Ground
Is the voltage greater than 10.5 V?
Yes No GO to B7. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - B7 CHECK THE PCM POWER RELAY
- PCM Power Relay connector disconnected.
- Carry out the PCM power relay component test. Refer to the OEM WIRING DIAGRAMS COMPONENT TESTING article.
Is a concern present?
Yes No INSTALL a new PCM Power Relay. Clear the PCM DTCs. REPEAT the self-test. GO to B8. - B8 CHECK THE PCMRC CIRCUIT FOR AN OPEN
- Ignition OFF.
- PCM connector disconnected.
- Measure the resistance between:
(+) PCM Power Relay Connector, Harness Side (-) PCM Connector, Harness Side PCMRC - Pin 2 PCMRC - Pin B1
Is the resistance less than 5 ohms?
Yes No GO to B9. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - B9 CHECK THE PCMRC CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between:
(+) PCM Power Relay Connector, Harness Side (-) PCMRC - Pin 2 Ground
Is the resistance greater than 10K ohms?
Yes No GO to B10. REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. - Measure the resistance between:
- B10 CHECK THE PCMRC CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition ON, engine OFF.
- Measure the voltage between:
(+) PCM Power Relay Connector, Harness Side (-) PCMRC - Pin 2 Ground
Is any voltage present?
Yes No REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. GO to B11. - B11 CHECK FOR AN OPEN VPWR CIRCUIT BETWEEN THE PCM AND THE PCM POWER RELAY
- Ignition OFF.
- Measure the resistance between:
(+) PCM Power Relay Connector, Harness Side (-) PCM Connector, Harness Side VPWR - Pin 5 VPWR - Pin B11, B12
Is the resistance less than 5 ohms?
Yes No GO to B12. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - B12 CHECK FOR A SHORT TO VOLTAGE ON THE VPWR CIRCUITS BETWEEN THE PCM AND THE PCM POWER RELAY
- Ignition ON, engine OFF.
- Measure the voltage between:
(+) PCM Power Relay Connector, Harness Side (-) VPWR - Pin 5 Ground
Is any voltage present?
Yes No REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. GO to B13. - B13 CHECK FOR CORRECT PCM OPERATION
- Ignition OFF.
- 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) , Programming the VID Block for a Replacement PCM. The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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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.
