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: Notes
Start engine and idle until vehicle reaches operating temperature. If engine does not start or stalls after starting, continue to perform this KOEO Self-Test. DO NOT depress the throttle on gasoline engine vehicles. Turn key off and wait 10 seconds. Activate self-test procedure by using a jumper wire or with appropriate test equipment. Turn key on, leaving engine off. Record all KOEO and Continuous Memory Codes.
If a Code 11 (pass code) is not received in the KOEO portion of the test, service the KOEO codes. See KOEO, KOER or CONTINUOUS CODE/TEST MENUS. If ECA will not output codes, go to TEST QA, step 1). If service codes are received, check the following procedures:
- If CHECK ENGINE or SERVICE ENGINE SOON light was on when the vehicle arrived for service, use recorded Continuous Memory Codes and reference code charts before addressing any other symptoms.
- If engine runs rough or idles rough, go to TEST A, step 1), except vehicles equipped with Distributorless Ignition System (DIS) or Electronic Distributorless Ignition System (EDIS) ignition systems. For vehicles equipped with DIS or EDIS ignition systems, use recorded Continuous Memory Codes and reference code charts.
- On DIS and EDIS vehicles only do the following: if Continuous Memory Codes 45, 46 or 48 were received during KOEO Self-Test, go to TEST N, step 13), on (DIS vehicles). If Codes 45, 46 or 48 were not received, go to TEST S, step 2).
- If vehicle is a no start, go to TEST A, step 1), except vehicles equipped with EDIS ignition. For EDIS vehicles, go to TEST AA, step 1).
- If vehicle displays a Code 11 (pass code) and has no symptoms as described in the previous steps, go to COMPUTED TIMING CHECK.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.
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