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.
Electronic Control Module (ECM)
According to signal received from O2 sensor, ECM judges, by comparing actual mixture against stoichometric range, whether exhaust gas at the manifold is rich or lean and issues signals to duty solenoids.
Air/fuel ratio is judged to be rich when voltage produced by the O2 sensor is higher than a set specified level. As a result, ECM issues signals to the duty solenoids to by-pass a greater quantity of air into the carburetor. This additional air leans the air/fuel mixture.
Air/fuel ratio is judged to be lean when voltage produced by the O2 sensor is lower than a set specified level. As a result, ECM issues signals to the duty solenoids to by-pass a lesser quantity of air into the carburetor. The elimination of air enriches the air/fuel mixture.
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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.