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.
Catalytic Converter Damaging Misfire
If the engine control module (ECM) detects a certain number of misfires during 200 engine revolutions, this is interpreted as misfiring which damages the three-way catalytic converter (TWC). The number of misfires that the engine control module (ECM) allows before interpreting it as misfiring depends on the load and engine speed range. the malfunction indicator lamp (MIL) flashes when the misfire occurs, and shines constantly once the diagnostic trouble code (DTC) is stored.
The engine control module (ECM) does not store specific diagnostic trouble codes (DTCs) for emission or catalytic converter damaging related misfires.
The engine control module (ECM) registers and stores the engine speed and load range and whether the engine is warm or cold when misfiring is detected.
If the misfire stops, the requirements for the engine speed, load parameters and engine temperature must be met without misfiring before the engine control module (ECM) will begin counting down to extinguish the malfunction indicator lamp (MIL) and erase the stored diagnostic trouble codes (DTCs) for misfiring
The number of misfires can be read off.
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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