P0131moderate severityPowertrain
O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
on 1998 BMW 528i 2.8L I6 M52 · RWD
What this code means
The upstream O2 sensor voltage on Bank 1 is staying below 0.45V, indicating a lean condition or sensor fault.
Symptoms
- Check Engine Light
- Lean running
- Poor fuel economy
- Rough idle
Common causes
- Vacuum leak
- Faulty O2 sensor
- Exhaust leak before sensor
- Low fuel pressure
- Faulty fuel injector
Diagnostic steps
- Check for vacuum leaks
- Monitor O2 sensor voltage
- Test fuel pressure
- Perform smoke test on intake
- Inspect O2 sensor
Repair notes
Fix vacuum or exhaust leak. Replace O2 sensor if confirmed faulty.
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29CC
Misfire Cylinder 1
29CD
Misfire Cylinder 2
29CE
Misfire Cylinder 3
29CF
Misfire Cylinder 4
29D0
Misfire Cylinder 5
29D1
Misfire Cylinder 6
29D2
Misfire Cylinder 7
29E0
Lambda Additive/Idle Adaptation Limit, Bank 1
29E1
Lambda Additive/Idle Adaptation Limit, Bank 2
29E2
Lambda Multiplicative Part-Load Adaptation Limit, Bank 1