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
The DIS ignition module sends a reference signal to the ECM when the engine is cranking. If the engine is under 400 RPM, The DIS ignition module controls ignition timing. When engine speeds exceeds 400 RPM, the ECM applies 5 volts to the by-pass line to switch spark timing to ECM control.
An open or grounded EST circuit will result in engine operating in a back-up ignition timing mode and the "SERVICE ENGINE SOON" warning light will come on. If EST fault is present the next time engine is started, Code 42 will be set.
NO RELATED
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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.