Intermittant/Bad O2 sensor?

jcs44 · 03-27-07, 08:36 AM

Is it possible to have an intermittant (or bad) O2 sensor that would cause an occasional misfire, causing the service engine light to come on, but NOT set a code? I've had this situation going on for about a month now, but it only happens after the car has not been driven for a few days.

Thanks, JCS44
96 LT4 Vert

bradfordsvettes · 03-27-07, 09:48 PM

i do not think a n o2 would give you a misfire but i supose anything is possible can you grab a code when the light is on ? I would suspect a bad ground or some other part failing maybe even ecm if it is not storing codes Steve

jcs44 · 03-28-07, 10:11 AM

What I've got is the service engine soon light coming on but not setting a code. The light goes off within a day, and it may then stay off for a few days, but eventually it comes back on. This began after having the plugs, water pump, and distributor cap and rotor replaced.

David-F · 03-31-07, 01:44 PM

What are you using to check for codes? If the service engine soon light comes on a code should set, especialy with a rough idle, unless there is a problem with the PCM if there is an internal problem in the PCM a light could come on and the engine run poorly and not set any codes you will need to have a scan tool hooked up to check for this you can also jump 4 to 12 on the ALDL connector to actavate the CCM diagnostics and check for codes in other modules were they may have lost communacation with the PCM, this is a good quick check to find falty PCMc in 90 to 96 in most cases you will set a code 41 in the CCM.

David Fulcher