DCAWD.com

So yesterday morning I get a check engine light as I'm driving to work. Before heading home I stopped at an Advance Auto Parts store and used their code reader to determine it was a "P0031 - Heater Circuit Low" fault.

This is apparently from the front A/F (O2) sensor on the exhaust header. Doing some light searching on teh innerw3bs finds that most people just replace the sensor for a part cost of $150-$200. A few others have found wires leading to the sensor were melted.

I'm thinking either the connectors were knocked loose from some of the recent work I've had done (turbo replacement and A/C repair) or I may actually need to get a new sensor. Thanks to ScoobyMods.com, replacing the sensor looks to be a fairly straightforward job (notwithstanding the actual removal of the sensor which, as others can attest to, can be a stubborn part to dislodge). So this weekend I can inspect the sensor and wires to see if they're simply knocked loose, or get a new sensor and do the replacement.

My question to the council is: Any thoughts as to other causes of this fault code?

--Alan

Not much that it could be other than that. Looks like the heater element has gone out. Since it's only used during starts, it should cause any problems for you. Now if the whole O2 sensor goes out, you'll start getting crappy mileage and it will run rough.

For those that don't know: An O2 sensor needs to heat up before it becomes accurate in detecting your AFR's. Even though the one that Alan is talking about is very close to the engine (~16"), it still needs to have a heater element to bring it up to temperature before the exhaust would do it normally. This is especially true during the winter, for obvious reasons.

Damnit, I wish I had read the boards last night! I would have brought my spare O2 sensor along with the , um 'other things' to work today. That way you could at least confirm it is the sensor itself, and not the circuit...
Shame on Julian for not remembering that I whored the sensor out to him before for troubleshooting

Oops, I did forget about that

Even with some PB Blaster I couldn't get the sensor out. And even if I could, I can't get a good enough view to figure out how to detach the cable from the little metal heat shield - thingy. So I think I'm going to let a shop do it.

Stay tuned...

--Alan