: Emissions System



Yaemish
11-20-03, 11:33 PM
A few weeks ago my service light went on and the control center flashed the message that it was the emissions system, a day later both messages went away and just the other day they came back. Any ideas on why this may have happened? I do quite a bit of in town driving and I never get on the gas hard, could this have anything t odo with it?

Allante North *
11-21-03, 03:43 PM
Check the codes to see if anything comes up. You might need O2 sensor replaced. Let us kno what you find, and someone can offer some advice.

mcowden
11-24-03, 01:13 PM
A few weeks ago my service light went on and the control center flashed the message that it was the emissions system, a day later both messages went away and just the other day they came back.
Yaemish, that is exactly the symptom I had when it was time to replace O2 sensor(s). Allante North* is exactly right. On a '96, there are 4 O2 sensors. One on the exhaust manifold for both cylinder banks (2), one before the catalytic converter, and one after the cat. The one that seems to go bad most frequently is the one before the catalytic. It's very easy to get to and change, assuming you have or can borrow an O2 sensor socket from AutoZone, Pep Boys, Advance Auto Parts, etc. The sensors range in price from $60-$85 each, and I think Bosch is the most common brand. When you go to buy new ones, remember that the pre- and post-catalytic sensors are called "rear" or "heated" O2 sensors and are different from the other two in that they have electric heaters in them. (That helps get them up to operating temperature so the system can go into closed loop operation sooner and more accurately control fuel usage) The two on either side of the engine do not have heaters and the wiring harness is different. I was able to change all 4 of them on my '96 SLS without much of a problem. I think I borrowed a long 3/8" extension from my neighbor to get at the one on the back side of the engine, but the two under the car were both very easy. Once the bad sensor(s) have been replaced, reset the PCM codes and the "Check Emissions System" message should not come back. As an added bonus, your mileage and performance should also be better, and you'll probably pass an emissions test! Don't let this problem go on for much longer or you risk clogging or burning up the catalytic converter and causing any number of engine problems and bad gas mileage.

Let us know if that answers your question and gets you going in the right direction. We'll do what we can to help...