P0139

DTC P0139: Secondary HO(2)S (Sensor 2) Circuit Slow Response

1. Reset the PCM.
2. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
3. Check the secondary HO(2)S (Sensor 2) output voltage at 3,000 rpm with the scan tool.

Does the voltage stay within 0.3 - 0.8 V for 2 minutes?

YES - Replace the secondary HO(2)S (Sensor 2).

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the secondary HO(2)S (Sensor 2) and the PCM.