P0139

DTC P0139: Slow Response in Secondary HO2S (Sensor 2) Circuit

1. Reset the ECM.
2. Start the engine. Hold the engine at 3,000 rpm with no load (in neutral) until the radiator fan comes on.
3. Check the Secondary HO2S (Sensor 2) output voltage at 3,000 rpm with the scan tool.

Does the voltage stay within 0.3 - 0.6 V for two minutes?

YES - Replace the Secondary HO2S (Sensor 2) and the Third HO2S (Sensor 3) *1.
* 1: '02-03 M/T models

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the Secondary HO2S (Sensor 2) and at the ECM.