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.
Circuit Description
When engine is first started, engine operates in open-loop operation, ignoring O2S signal and calculating air/fuel ratio based on inputs from the ECT, TP and MAP sensors only. PCM will begin using O2S signal for controlling fuel delivery (closed-loop) when O2S has a varying voltage output showing that it is hot enough to operate properly and ECT has increased a minimum amount based on ECT at engine start-up.
For duplication of DTC, ensure:
- DTCs P0107, P0108, P0117, P0118, P0122, P0123, P0131, P0132, P0134, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0325, P0336, P0440, P0442, P0446, P0502, P0601, P0602, P1441 or P1621 are not set.
- Engine running for greater than 65 seconds.
- Engine speed at 1200-3400 RPM.
- TP sensor angle is 10-40 percent.
- ECT greater than 149°F (65°C).
- Above conditions have been met for 2 seconds.
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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.