Service Engine Light

I have a 97' Pontiac GT with 102k on it. The service engine soon light has come on for about the 3rd time in the last year. The first two times was because a piece of carbon got on the oxygen sensor. Who much does it cost to replace the sensor because the last time they cleaned it didn't work?

What code are you getting? I have a 2000 GP that kept throwing a code showing low votage to bank 1 O2 sensor. After multiple sensor changes, etc. it turned out to be a fuel filter. The engine was getting insufficient fuel apparently even though the pressure was fine. It had a lot of people, dealer included, stumped. Car has been fine since.

I think Delco O2 sensor replacements (4 wire, heated) are in the $80-100 range.

You can generally change it if you can get access to a 7/8" or 22mm box end wrench inside the vehicle. It does not require all the torque that this size wrench can potentially provide when installing the new one. I would also make sure they did not gob on the anti-seize compound as excess can enter and kill off the sensor. It just needs a light "precision" coat of anti-seize to the threads only....I use the grey nickel-based formulation.

If new O2 sensors don't resolve the SES problem, there's a chance there is a bad ground connection somewhere. O2 feedback is a millivolt signal, and so it doesn't take much resistance to screw up that signal.

helicopter23,

It doesn't do much good removing and cleaning the 02 sensor over and over again when you have another issue causing the SES/CEL light. I recall at one time you had a P0135 DTC which is an issue with the heater element of the pre-CAT 02 sensor so obviously cleaning it is not helping. First get it scanned again as suggested and if the same DTC is present start by the checking the 12 volt input to the heater portion of the 02 sensor at the electrical connector. Also, post any other DTCs if present.

If the 02 sensor turns out to be bad you can get an AC Delco replacement, PN: AFS109 at vendors on Ebay or our typical Grand Prix suppliers. Also, the Denso brand 02 sensor works fine as a suitable replacement. You're looking at around $40-$50 for either brand. The GM dealers will be more expensive.

helicopter23,

It doesn't do much good removing and cleaning the 02 sensor over and over again when you have another issue causing the SES/CEL light. I recall at one time you had a P0135 DTC which is an issue with the heater element of the pre-CAT 02 sensor so obviously cleaning it is not helping. First get it scanned again as suggested and if the same DTC is present start by the checking the 12 volt input to the heater portion of the 02 sensor at the electrical connector. Also, post any other DTCs if present.

If the 02 sensor turns out to be bad you can get an AC Delco replacement, PN: AFS109 at vendors on Ebay or our typical Grand Prix suppliers. Also, the Denso brand 02 sensor works fine as a suitable replacement. You're looking at around $40-$50 for either brand. The GM dealers will be more expensive.


I drove the car today and the service light disappered, how could that be?

Keep you posted

Oh well. :lol:

It sounds like you have been having this intermittent problem on and off for awhile. It is possible for the SES/CEL light to clear after a few or several drive cycles or when the PCM runs the test on the sensor and it passes. There are different types or classifications of DTCs. Type A, B, C, etc. Even with the SES light off you can still have a code stored in history. If it were me I would run a real-time or live sensor data (PID) diagnostics with a full function scan tool or program like Autotap or similar.

$100