P1131moderate severityPowertrain
HO2S Circuit Low Variance Lean Indication
on 1996 Volvo 960 2.9L I6 · FWD
What this code means
The ECM detected that the upstream O2 sensor is showing a persistent lean-biased signal with insufficient switching activity. The sensor is stuck or sluggish on the lean side.
Symptoms
- Check Engine Light
- Poor fuel economy
- Rough idle
- Failed emissions test
Common causes
- Aging O2 sensor with degraded response
- Exhaust leak before O2 sensor
- Vacuum leak causing actual lean condition
- Contaminated O2 sensor
- Wiring issue affecting sensor output
Diagnostic steps
- Monitor O2 sensor signal switching with scan tool
- Check for exhaust leaks
- Perform smoke test for vacuum leaks
- Inspect O2 sensor for contamination
- Test sensor wiring
Repair notes
Replace the upstream O2 sensor if switching response has degraded.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1