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.
Diagnostic Aids
Perform this circuit test when directed by other CIRCUIT TESTS. This test is intended to diagnose only the following:
- ECA
- Throttle plate linkage
1) Check For Codes 23, 53, 63, 121, 122 Or 123 If vehicle is equipped with a speed control, speed control servo must be electrically disconnected. This prevents speed control system from affecting throttle plate movement during Output State Check. Rerun QUICK TEST or Output State Check.
Turn ignition off and wait 10 seconds. Perform KOEO SELF-TEST. If Codes 23, 53, 63, 121, 122 or 123 are displayed, go to appropriate KOEO SELF-TEST CODES chart under SERVICE CODE REFERENCE CHARTS and service code(s) as necessary. If no code is displayed, go to TEST QA, step 1). If Code 11/111 (pass code) is displayed, go to next step.
2) Check Throttle Linkage Check throttle and linkage for sticking or binding. If throttle and linkage are okay, replace TPS and repeat QUICK TEST. If throttle and linkage are binding, repair as necessary and repeat QUICK TEST.
Use the Manual With the Right Hardware
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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.
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