Hey guys maybe you can shead some light on my problem. I have a 98 Z28. My check engine light came on three days ago. I scaned the code and it came up as P0135 (Oxygen sensor heater circuit malfunction pre-converter sensor, left bank). I have long tube headers with the off road Y-pipe. I have Casper o2 simulators. I also had the car tuned a year ago and the guy that tuned it said he deleted the o2 sensor codes so I dont even need simulators but I left them on anyways. I've had this set up for about a year now and never had a check engine light. I checked all the wires and they look intacted and pulled the o2 sensors wiped a little carbon build up off them but not much. The o2 simulators have these red lights on them that blink off and on when the car is on, not sure if thats normal or what. Any info is much appreciated. Thanks

 

The pre cat is the first o2 sensor, left bank is drivers side IIRC,(the one the pcm uses to adjust the fuel trims) the rears having been tuned out shouldn't throw any codes
FWIW I used the bosch 13111 o2 sensors on my headers and havent had any problems with codes
You might just need to replace the front o2s

 

are the front sensors on the collector of the headers or up higher by the engine?

 

If you don't have headers, then yes the o2's are further up. Otherwise if you have headers they should be at the collectors.

 

The front sensors are on the collectors of the headers, and right by the manifolds if you have stockers.

Your problem lies in the heater, which is common to people with LT headers. A simple fix is to swap out to new Bosch PN 13111 O2 sensors. These are corvette REARS and have a stronger heater due to them being placed so far back in the corvette's exhaust system. Here's a link to the cheapest I've ever seen them....

http://rep.speedycarparts.com/parts/...gory=C&dp=true