P0139

Tests 276 - 279:

Tests 280 - 281:

SYMPTOM
P-0139 1/2 O2 SENSOR SLOW RESPONSE

WHEN MONITORED
With engine temperature > 147 degrees F, after reaching a vehicle speed of 10 mph, and the throttle remaining open (off idle) for two minutes, bring the vehicle to a stop, allow engine to idle with the transmission in drive (auto) or in neutral (manual).

SET CONDITION
The oxygen sensor signal voltage is switching from below 0.27 volts to above 0.62 volts and back fewer times than required.

POSSIBLE CAUSES
- 1/2 O2 sensor ground circuit open
- Oil or coolant consumption
- 1/2 O2 sensor defective
- 1/2 O2 sensor terminal observable defect
- Exhaust system leaks
- PCM terminal observable defect