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.
KOEO Self-Test
Ensure engine is at normal operating temperature. If engine does not start (or stalls after starting), continue KOEO SELF-TEST. DO NOT depress throttle on gasoline vehicles. Turn ignition off. Wait 10 seconds. Ensure test equipment is properly attached. Turn ignition on (engine off). Record all KOEO and Continuous Memory Codes.
If a Code 11 or 111 (pass code) is not retrieved in KOEO portion of test, service KOEO codes at this time. Service any engine codes recorded before servicing transmission codes (codes No. 566 and 629). If PCM will not output codes, see appropriate TESTS W/CODES article in ENGINE PERFORMANCE. If service codes are retrieved observe the following procedures:
- If CHECK ENGINE or SERVICE ENGINE SOON light is on, service codes in order retrieved.
- On vehicles equipped with DIS and EDIS ignition systems, see appropriate SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
- If Continuous Memory Code 211, 212, 215, 216, 217, 232 or 238 is retrieved during KOEO SELF-TEST. Repair ignition system as necessary.
- If vehicle has a no-start condition, go to CIRCUIT TEST AA, AB or AC in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section.
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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.