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.
O2 Sensor Circuit
Diagnostic conditions
- Exhaust temperature between 250°C and 750°C
- Battery voltage between 10 V and 16 V
- Time elapsed after engine start-up greater than 200 seconds
- No secondary air
- No diagnosis of secondary air system
- No fuel tank ventilation
- No diagnosis of fuel tank ventilation system
- No other oxygen sensor faults
Possible cause of fault
- Short circuit to ground in signal wire
- Intercore short circuit
Affected terminals
DME control module connector II, pin 8 and oxygen sensor jack, bank 1, pin 3
DME control module connector II, pin 14 and oxygen sensor jack, bank 1, pin 4
Diagnosis/troubleshooting
- Do not use contact spray on the oxygen sensor plug connections as this may cause irreparable damage to the wiring (contamination of the oxygen sensor via the reference air channel).
Use the Manual With the Right Hardware
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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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