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.
Code 45 - Rich Exhaust Indication: Notes
The ECM supplies a voltage of about .45 volts between circuits No. 412 and 413. The O2 sensor varies the voltage from one volt (rich exhaust) to .10 volt (lean exhaust). The sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is below 600°F (316°C). An open sensor circuit or cold sensor causes open loop operation.
Code 45 is set when O2 sensor signal at ECM is above .75 volts for 50 seconds and time since engine start is one minute or more. Code 45 indicates a rich exhaust and diagnosis should begin with these items: fuel pressure, leaking injector, HEI shielding, canister purge saturation, coolant sensor, MAP sensor, O2 sensor contamination and TPS intermittent output.
- Checks to see if O2 sensor is registering a rich condition.
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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.