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, Non-Heated O2 Sens CKT, Rich Exhaust Indicated: Notes
ECM supplies approximately .45 volt between ECM terminals D6 and D7. If voltage is measured with a 10-megohm DVOM, reading may be as low as .32 volt. Oxygen (O2) sensor produces a varying voltage to ECM as engine reaches normal operating temperature. Voltage varies between .1 (lean) and 1.0 (rich) volt depending on conditions of exhaust gases in exhaust manifold.
O2 sensor will not produce voltage until sensor reaches 600°F (316°C). When sensor is less than specified, open loop condition exists.
- Code 45 will set when O2 sensor signal voltage is fixed at greater than .75 volt (750 mV) and with the following conditions:
- Throttle Position (TP) sensor is greater than 3 percent.
- No Code 21 or Code 33.
- System is operating in closed loop.
- Engine coolant temperature is greater than 155°F (69.5°C).
- Short term fuel trim is not at 128.
- Vehicle Speed Sensor (VSS) is greater than 3 MPH.
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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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