What does it mean?
P1137 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: HO2S-12 Low Voltage During Power Enrichment .
Symptoms
- Malfunction indicator lamp on, often after a spell of hard acceleration
- Loss of power or a flat feeling at full throttle
- Occasional lean surge or hesitation when the engine is pushed
- Ticking or blowing sound from under the vehicle indicating an exhaust leak
- Fuel economy worse than usual on mixed driving
Likely causes
- Exhaust leak between the catalytic converter and the rear sensor drawing in air
- Aged or contaminated rear oxygen sensor that no longer swings to high voltage
- Fuel delivery falling short at wide open throttle because of a weak pump, restricted filter or low rail pressure
- Restricted or partly melted catalyst substrate disturbing flow past the sensor
- High resistance or a poor ground in the rear sensor signal circuit pulling the reading down
- Sensor pigtail chafed against the underbody or heat shield
- Injector flow restriction on that bank limiting the commanded enrichment
How to fix it
- Log the rear sensor voltage during a full throttle pull and confirm it fails to rise with commanded enrichment
- Inspect the exhaust between the converter and the rear sensor, then smoke test to expose small leaks
- Check fuel pressure and volume under load rather than at idle only
- Compare front and rear sensor traces; if the front sensor confirms rich but the rear does not, the rear circuit or sensor is suspect
- Measure the rear sensor signal and ground circuits for resistance and continuity to the PCM
- Inspect the pigtail for chafing and heat damage along its routing
- Replace the rear sensor after the exhaust and fuel sides prove good, then repeat the enrichment test