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 P045, Rear Oxygen Sensor Rich Signal: Notes
PCM provides a .45-volt reference signal to oxygen sensor on circuit No. 1670. When oxygen sensor temperature is less than 392°F (200°C), sensor signal voltage will be about .45 volt and PCM will keep system in open loop operation. When oxygen sensor temperature is greater than 392°F (200°C), sensor will swing from rich to lean rapidly, at least one swing every 2 seconds, if PCM is in good control of air/fuel mixture.
Code P045 sets when sensor stays at a rich voltage for more than 50 seconds during the test conditions. Code P045 will also set when oxygen sensor circuit fails or when air/fuel ratio is actually rich due to fuel control or emissions system fault.
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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.