P0138

DTC P0138 O2 Sensor Circuit High Voltage




CIRCUIT DIAGRAM




INSPECTION PROCEDURE

TROUBLESHOOTING HINTS
1. If the heated oxygen sensor is defective abnormally, high emissions may occur.
2. If the heated oxygen sensor check has been normal, but the sensor output voltage is out of specification, check the following items related to the air fuel ratio control system.
- Faulty injector.
- Air leaks in the intake manifold.
- Faulty mass air flow sensor, EVAP valve and engine coolant temperature sensor.
- Wiring connection problem.
3. When O2 sensor output voltage is maintained as following for above 50 seconds.
- Upstream: 0.4V - 0.6V
- Downstream : 0.4V - 0.5V

When the lean/rich period is above 2.6seconds in the condition that fully warm-up engine is 2,000 - 3,000 r.p.m and engine is above middle load.