I have a perplexing problem that has been haunting my 1994 850 Turbo Wagon for several years. The Check Engine light is on most of the time. My dealer always finds that the code indicates a bad Knock Sensor. The sensors have been replaced 3 times and the ECU 1 time without any change in the warning light behavior. The problem started a few months after purchasing the car new. The car was in an accident early in its life but the timing of the light is not directly matched to the accident (but close).

Although the car runs fine, I’m tired of looking a light that has become meaningless. Can anyone suggest a course of action other that removing the light bulb?

I looked through the archives and could not find anything that directly addressed my problem but I did see mention of wiring updates. I have also heard that grounding problems can cause weird behavior.

Thanx for your help.

Eric

Have had the check engine light on for several months... I reset it and it comes back on... I changed the oil on Sunday and the light went out immediately... On startup, the car blew a little puff of smoke and then cleared and has run clean ever since. I'm baffled, but cautiously happy. I do know that I have a few vacuum leaks, and my transmission fluid needs replacing (due this weekend), but it's running..

Very Good Luck to You!

Shawn

dude, I feel your pain on the knock sensor. You can ck the knock sensor by putting a ohm meter on it. I went ahead and replace the knock sensor which involve removing the intake manifold. Two days later the ck engine light came back on and found out the connection was dirty. All you need to do is clean the connection, place electric grease, and reset the ecu(or it will do it by itself). If u don't know where the connection is - it is about middle of radiator and zip tie to bottom of cross bar.

good luck.

Thanks for the great tip! Was about to have an Indy replace the front knock sensor; 94 850T. While changing the oil cleaned both contacts from the front knock sensor (2 wired connection) cleared codes last 2 months no CEL.

Yes I know how you feel I too have the same problem with code 143 front knock sensor I so I buy and up grade kit and replace it comepletely... after 2 day hard work the light come back on again and again....

I keep clear it out but it keep come back so I said screw it the car run fine I just ignor it what else can we do..

I reset clean the connector ever thing there is to do...

You can put a small piece of Black tape over the light....


If you realy want to remove the light go to bay13 it show you all the detail

but why ?? just put tape over the light...

Eric,
The check engine lamp will be triggered if any fault is found (and hopefully stored) that can effect the exhaust emissions. Even some transmission faults can effect the emission output, causing the lamp to light up. Has the dealer check for ALL fault codes. If so, start thinking about things you have not maintained or are over due for replacement that could effect the emmisions. Anything from bad gas to faulty plugs to a dirty air filter could effect the emmisions.

Eric,
The check engine lamp will be triggered if any fault is found (and hopefully stored) that can effect the exhaust emissions. Even some transmission faults can effect the emission output, causing the lamp to light up. Has the dealer check for ALL fault codes. If so, start thinking about things you have not maintained or are over due for replacement that could effect the emmisions. Anything from bad gas to faulty plugs to a dirty air filter could effect the emmisions.