P0139low severityPowertrain
O2 Sensor Circuit Slow Response Bank 1 Sensor 2
on 2010 Subaru Forester 2.5L H4 · AWD
What this code means
The downstream O2 sensor on Bank 1 is responding too slowly.
Symptoms
- Check Engine Light
- Failed emissions
Common causes
- Aging sensor
- Contaminated sensor
- Catalyst issue
Diagnostic steps
- Monitor sensor response
- Check catalyst efficiency
Repair notes
Replace downstream O2 sensor.
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