Re: PO139 WTF
1. Reset the ECM/PCM
2. Start the engine . Hold the engine at 3,000 rpm without load until the radiator fan comes on.
3. Check the secondary HO2S (sensor 2) output voltage with a scan tool.
Is there 0.3- 0.8 volts?
YES- Replace the secondary HO2S (sensor 2) and the third HO2S (sensor 3). They must be replaced together.
NO- Intermittent failure, check for lose connections at the secondary HO2S and at the ECM/PCM.