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.
Malfunction Indicator Light (MIL)
1) Check MIL operation. Turn ignition on. If MIL is on, MIL circuit is okay. Go to next step. If MIL is off, go to TEST MIL. After performing TEST MIL, return to this procedure.
2) Connect a jumper wire between ground and PCM STI terminal of Data Link Connector (DLC). See Figure. Turn ignition on. Observe MIL and record pulses to determine KOEO codes stored.
3) If codes are not present, go to next step. If codes are present, go to step 5).
4) If engine starts, go to step 7) to begin KOER self-test. If engine does not start, go to appropriate BASIC TESTING article in this section.
5) Erase codes from PCM memory. See CLEARING CODES. Repeat step 2) to identify hard faults. If code does not reappear, fault is intermittent. Go to step 7) to begin KOER self-test. If code reappears, indicating hard fault, repair fault as necessary. See appropriate CODE REFERENCE CHART table to determine circuit test to perform. Go to next step.
6) Repeat step 5) until no code appears. Terminate KOEO self-test by turning ignition off and disconnecting jumper wire from PCM STI terminal. Go to next step to begin KOER self-test.
7) Start and operate engine at 2000 RPM for 3 minutes to ensure HO2S/O2S sensor is operating. Ensure vehicle is at normal operating temperature. Connect jumper wire between ground and PCM STI terminal of DLC. Observe MIL. Record pulses to determine KOER codes stored. Use appropriate CODE REFERENCE CHART table to determine circuit test to perform.
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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.