Diagnostic Code Interpretation.

[Mr. Curious]

My SC400 is throwing codes 21 (Main O2S & Heater Signal) and 28 (Main O2S). Which O2 sensors are the main sensors? The pair before or after that cats? What is the "Heater Signal"? Can I solve the code 28 by replacing the malfuntioning O2 sensor(s)? Where's the place to get an O2 sensor for my SC for a good price?

Thanks.

[BMAN1113]

If I remember right someone on here said that only the O2's before the cats go bad. So I would guess that it would be one of the front two. I would just replace them both to make sure everything is running smooth. Often these sensors will stop functioning properly, to some degree, even before the cars diagnostics system catches them. There are a lot of internet sources just Google search "O2 sensor SC400". I'm about to have to get some too I think. I'm getting slight "bucking" at low speed and its just not as spunky as it used to be. Just try the two before the cats first.

[BMAN1113]

Also, I would definately stick with the Denso line.

[SKperformance]

get a motorvac,

mention the year of the car next time

[Mr. Curious]

Also, I would definately stick with the Denso line.

what makes you say that? actually, i cant find any place that sells the applicable denos sensors; i can only find bosch, acdelco, and standard motor products sensors for my sc.

[BMAN1113]

I've had friends who would buy Bosch parts for Porsche and VW. The life seems too short. I just think Denso is a higher quality. You can find Denso all over the net. I just think Bosch is over rated... Like a lot of items from Germany.