P0138

Tests 1 - 5:

Tests 6 - 11:

Test 12:

SYMPTOM
P0138 1/2 O2 SENSOR SHORTED TO VOLTAGE

WHEN MONITORED
With battery voltage greater than 10.4 volts, engine running for more than 4 minutes and coolant temperature above 180 °F.

SET CONDITION
The oxygen sensor voltage is above 1.5 volts.

POSSIBLE CAUSES
- O2S heater feed circuit open
- O2S heater ground circuit open
- O2S sensor ground circuit open
- O2S signal circuit open
- O2S signal circuit shorted to voltage
- Wiring harness intermittent defect
- PCM internal short
- O2S shorted to voltage