Contour Enthusiasts Group Archives Forums General Troubleshooting o2 sensor help!

can anyone explain in some detail what CEL code P0136 means? It reads: "downstream heated oxygen sensor circuit fault- bank 1."

I've got a '99 contour SVT (v6).

Ask and you shall receive.
From the Service CD:
DTC P0136 and/or P0156 indicates the output voltage of the downstream HO2S is less than some calibratable functional window. (That's easy for them to say, I have no idea what this is saying, really.)

Possible causes:

l Wiring Concerns:

-- Pinched, shorted, and corroded wiring and pins

-- Crossed sensor wires

l Other Concerns:

-- Exhaust leaks

-- Contaminated or damaged sensor


l Are any of the above concerns present?

Yes
REPAIR as necessary. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».

If the above items check out OK, then there is some intermittent problem and the manual sends you to a general Pinpoint Test. Basically, you need to check the above possible causes, then reset the PCM and see if the code returns. If it does, you have some sort of intermittent fault and it's off to a shop that specializes in electrical auto problems.

I just replaced my bank 1 downstream O2 sensor in hopes of remedying a P0420 code. I noticed two things in the process:

• The sensor pigtail (i.e., the wires between the plug and the sensor head) is routed through a metal clip connected to the tranny case (at least, it is on my '98 SVT). If not properly routed, the pigtail could rub against one of the halfshafts or contact a very hot surface, either of which could conceivably end up messing up the circuit.
  
• When I unplugged the old sensor, there was a fair bit of grit in/around the connector, which might interfere with making a good contact.

Anyway, hope this helps. Being able to remedy the problem by replacing the sensor would be far preferable to tracking down a fault deep inside the wiring harness...

special thanks to both of you!