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.
Est Signal
When in the EST mode, ECM controls EST and compensates for all driving conditions. If ECM has an internal failure of the EST system, this will cause ECM to operate in an ignition timing back-up mode. The "SERVICE ENGINE SOON" light will illuminate. If the EST fault is present the next time the engine is started, Code 42 will be set. An open or grounded EST circuit will cause engine to stall. Engine will restart; however, engine will stall again once by-pass line tries to reactivate EST mode.
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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.