P0138

Description
HO2S 2 CIRCUIT VOLTAGE HIGH

Three-Way Catalyst (TWC) system is used to control emissions.
PCM uses signal from Heated Oxygen Sensor (HO2S) behind TWC to read
efficiency of TWC. PCM will set DTC P0137 if TWC oxygen storage
capacity is less than a predetermined threshold.
Symptoms
There may be no noticeable symptoms except for MIL light. Engine might be running rich.

Causes

• Faulty O2 sensor
• Short to battery voltage in O2 sensor signal circuit
• High fuel pressure

Possible Solutions

• Replace O2 sensor
• Repair short to battery voltage in o2 sensor signal circuit
• Disconnect MAF sensor connector and see if rich condition is corrected. If rich
  condition is corrected, replace MAF sensor.