Oxygen O2 Sensor Circuit Low Voltage
Three-Way Catalyst (TWC) system is used to control emissions.
PCM uses signal from Heated Oxygen Sensor (HO2S) located behind TWC to read efficiency of TWC. PCM will set DTC P0137 if TWC oxygen storage
capacity is less than a predetermined threshold.
There may be no visible symptoms to the driver, other than the MIL, Check Engine light.
- Faulty o2 sensor Exhaust leak near the rear sensor
- Plugged catalyst
- Short to voltage on O2 signal circuit
- High resistance or open on O2 signal circuit
- Vacuum leak
- Replace O2 sensor
- Repair exhaust leak near the rear sensor
- Check for restriction in catalyst and replace as necessary
- Repair short, open, or high resistance on o2 signal circuit
- Check for vacuum leaks at intake manifold, throttle body, EGR
system and crankcase ventilation system.
- Disconnect MAF sensor connector and see if lean
condition is corrected. If lean condition is corrected, replace MAF