Hello S owners,

I just picked up my first S here in CA and have 3 CEL that I need help with before I can smog the car.

P0325 / P0138 / P0136

I know the P0325 is the knock sensor circuit malfunction so I'm planning to replace the sensor.

P0138 and P0136, I gathered it is related to the O2 sensor in the testpipe but I'm not sure what the fault code is. Would replacing the O2 fix both these two codes?

Thanks a bunch!

 

Actually, will adding a catalytic converter back onto the car fix the P0138 and P0136? Or is it a bad O2 sensor?

 

Bad sensor or a wiring problem. P0136 seems to be a temporary "something's out of whack with the O2 sensor system" code. The ECU then throws something more specific when a problem's been confirmed. Which is for you, code P0138. If you fix P0138 then P0136 should be fixed as well.

P0138 = Secondary HO2S( Sensor2 ) Circuit High Voltage.

A break in the signal wire between the ECU and O2 sensor will throw this code. When I bought my car the last owner ran an AEM EMS; they depinned the stock O2 sensor wire (to use a wideband O2) but didn't replace the stock O2 pin when they put a stock ECU back in.
I threw a similar "Circuit voltage high" code for the primary O2 and it was solved by simply plugging the pin back into the ECU harness.

I'd imagine a sensor failure could cause a similar problem.

I don't think putting a cat in will help with this code, this code is describing an electrical fault, not an efficiency fault like I think you'd get with no cat.
You might still need to get a cat though; once P0138's fixed you may get another code specifically for low catalyst efficiency.
Not to mention if smog involves them sticking a sensor in your tailpipe (hellllooooo!) they're gonna see high/abnormal emissions without a cat, dunno if it will fail but maybe someone else does.

Any good with a multi-meter? The service manual tells you how to test the wiring, might be worth a try instead of spending a bunch on a new O2, just to find out a wire was pinched or cut or whatever, same with the knock.

 

I am going to go under the car tomorrow to see if there are any obvious damage or disconnect to the O2 sensor.

Did the knock sensor today and found there was nothing in the hole. The sensor itself was in the cracks below after it was attempted by the previous owner. Tried to put the new sensor in and lost it when it dropped from my hand. Searched for 30 minutes to no avail. There goes $160.