I was driving around last night, when my CEL came on what seemed random to me. I pull over, check everything out that I can. I can't find or hear anything out of the ordinary. Well I take my car to Advanced Auto Parts, and they retrieve the engine code for me. I engine code I got was P0138, Secondary Heated Oxygen Sensor Circuit High Voltage (Sensor 2). I have a K&N Typhoon Cold Air Intake and a Megan Racing Test Pipe. I have three spark plug anti-foulers installed for the use of my test pipe. Two of them are long, and the third one is shorter and came with the test pipe from the previous owner. I've probably put on close to 2,500 miles since I installed the test pipe. Will an engine code like that put my car in "limp mode"? Any suggestions?

 

P0138 is for a secondary 02 sensor circuit high voltage. You'll need to check the connector at the 02, make sure it's locked in. The secondary heated oxygen sensor (HO2S) (Sensor 2) is installed downstream of the three way catalytic converter (TWC). The HO2S detects the oxygen content in the exhaust gas downstream of the TWC during stoichiometric air/fuel ratio feedback control by the engine control module (ECM) from the primary heated oxygen sensor (HO2S) (Sensor 1) output voltage, and its output voltage is used to control the air/fuel ratio so that the TWC efficiency is optimized. Experiences I've had with bad O2 sensors have been REALLY bad gas and the O2 sensors getting fouled. Check the wires too. Bare wire shorting out happens.

 

I think you have the sensor spaced out too far. Two spacers have served me well for about ~8K miles.

 

yep, too many spacers. one long, and one short is perfect.
i have 50k+ miles on that exact setup, and no light. youll be just fine. 3 is overkill.

 

More is not better here. If you take the 2' O2 sensor out of the exhaust stream, it'll trigger a CEL. Maybe aim to keep the tip ~1/2cm-1cm recessed. Anything farther will make the ECU think the O2 sensor is faulty.

 

loose that dirty test pipe ...or just screw the world

 

I'm about to just remove the test pipe, and put my catalytic converter back on. I'm pretty sure I got it fixed though. Two of the spark plug anti-foulers were loose. Just got to reset the CEL, and hope it doesn't come back on.

 

Boycott NHRA and NASCAR, too.

 

I like my test pipe.