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 (DOHC) - O2 Sensor Rich Fuel Mixture (Heated Sensor): Notes
The ECM supplies a voltage of approximately .45 volt between ECM terminals D6 and D7 (if measurement is taken with a 10-megohm DVOM, reading may be as low as .32 volt). The O2 sensor varies voltage from approximately .1 volt (lean exhaust) to 1.0 volt (rich exhaust). When sensor temperature is less than 600°F (316°C), the sensor acts like an open circuit and will not produce voltage. An open sensor circuit or cold sensor will cause an open loop condition.
- Code 45 will set when sensor voltage signal is greater than .75 volt under following conditions:
- Coolant temperature is greater than 157°F (69.5°C).
- Integrator count is not at 128.
- No Code 21A, 21B, 33A or 33B is set.
- TPS is greater than 10 percent (A/T) or 8 percent (M/T).
- System is in closed loop.
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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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