This is about the 4th set of front Oxygen sensors I've had on my car and the passenger side always goes out. I've only had the new ones in for about 3 weeks and it keeps throwing the heater circuit malfuntion code for the passenger side O2 sensor. What keeps causing this? At 1st I thought it was because I had a different spark plug in the passenger side (got an NGK Iridium in the mail with a broken tip so put old Bosch +4 back in until new one arrived) but have since put the new one in and it still malfunctions. It's happened since I've had my PCM reprogrammed, deleted EGR and AIR, put on Dynatech 1.75" long tube headers where the O2's go in the collectors, and have just recently done Opti, coil, and ignition control module. Could there be something wrong with my O2 plug in wire extensions? I'm not sure what else it could be.

 

Yeah, I would check the terminals in your extensions. Make sure you get power on the pink wire (cavity "D") to ground when the key is ON. If you have a scanner or scan software, you can also check what it says for O2 voltage with the key ON (not started).

 

Well I took the extension out to just look at it and see if there was a wire burnt and it looks like it did hit the header at some point and the purple wire was burnt through and stuck to the other wires. So I seperated the wires and electrical taped them all one by one and routed the extension differently now by going down the side of the tranny as opposed to the firewall. Seems to run better already.