PO139 WTF
 

anyways the CEL came on after a very grueling 16 hour work day In my 05 civic SE

checked it when i got home po139 meaning o2 sensor ckt #2 slow response.

What does this mean? is it just dirty? usually if it was gone it would say no activity, so im stumped.

Any input?

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.