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.
Testing Procedure
O2 Signal - Connect DVOM between left cylinder bank ME-SFI control module connector 1 terminals No. 40 and 42 (socket box terminals No. 40 and 42). Start engine and idle. Keep engine speed between 2000-3000 RPM for approximately 2 minutes after engine coolant temperature reaches more than 176°F (80°C). Allow engine to idle. Voltage must exceed or drop to less than 450-500 millivolts within one minute. If voltage is okay, test is complete. If voltage is not okay, possible causes are left O2 sensor (after TWC) heater failure, wiring harness failure, defective left O2 sensor (after TWC - G3/5) or defective left cylinder bank ME-SFI control module (N3/11). To check left O2 sensor (after TWC) heater failure, go to DTC P0161: O2 SENSOR HEATING OF LEFT O2 SENSOR DOWNSTREAM TWC (G3/5) .
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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.