Ensure engine is warmed to 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. See SERVICE CODE REFERENCE CHARTS . If ECA will not output codes, go to CIRCUIT TEST QA. If service codes are retrieved:

If CHECK ENGINE or SERVICE ENGINE SOON light is on, service codes in order retrieved. See SERVICE CODE REFERENCE CHARTS .
On DIS and EDIS models, see IGNITION SYSTEM in I - EEC-IV SYS/COMP TESTS article in the ENGINE PERFORMANCE Section if Continuous Memory Code 45, 46, 48, 215, 216, 217, 232 or 238 is retrieved during KOEO SELF-TEST.
If vehicle has a no-start condition, go to CIRCUIT TEST AA (TFI), CIRCUIT TEST AB (DIS) or CIRCUIT TEST AC (EDIS).
If vehicle displays a Code 11 or 111 (pass code) and does not have any of symptoms described in previous steps, go to COMPUTED TIMING CHECK.

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.

Safety Warning

KOEO Self-Test

Use the Manual With the Right Hardware

When to See a Mechanic