I have had the light on for a couple of weeks now. No problems with the engine. I am assuming it is a O2 sensor of the MAF. Car has 90k on it. I went to Autozone to use the scan tool, and apparently the Peoples Republic of California has forbid auto parts stores from renting the OBD tool. What are the odds it is the MAF.

You will want to check your intake boots, both the one going to the airbox and the one going to the throttle body/ icv. On my X5, the boot had disintegrated slightly and over long periods of time would activate the CEL for creating a lean condition. While you're there, buy MAF cleaner (not brake cleaner) and follow those instructions to free up some mileage. Also a good time to check the air filter!

Original CEL/SES light was for the emissions but over time the connector became more "computerized"... think of it as an USB port to your car... with proper software you can control the lights, the suspension, other things with a computer connected to the OBD connector...

so, when the light is on, it is best not to guess, as to what might be wrong but to get the proper reader and check the codes... also, one needs to bear in mind, that some codes might be secondary to a problem, say you have a problem upstream, somewhere in the air intake but the code is reading a problem downstream, in the cats... an experienced mechanic can differentiate between the real downstream issue and the issue upstream that sets off downstream indicator...

get a real code reader - or get a USB-to-OBD cable, get the INPA software along with the SSS and the rest, get yourself an old laptop with XP Pro, and do the testing/reading yourself... you will also be able to read errors in the other modules, you will be able to program some minor things to your liking...

I have checked the intakes and they look good. Within the last two years I have had a new throttle body installed and had the CVV checked out. The mech said the CVV and hoses all looked good and it was only a bad valve cover gasket. With that said the MAF looks good, but is original with 90k on it. The car has been a California desert car so that has helped, except for the interior.

wow - blast from the past!

No kidding.

So, how's your 4.4i been the last few years?

My SES light is permamently on, it is due to the fact that I have added LPG fuel system to the car.So the fault code always tells me there is a problem with my speedo/tach/fuel sensor cos the car is doing 250miles more per tank of fuel than is possible :D:D.poor thing cant compute that im going so far on one tank of petrol.
The light sometimes goes out after I fill both tanks to the brim, but normally returns again within a few days.

had ses light come one once at me... took out my diagnostic stuff, reset everything and been fine for the next 5 months. Winning! first clear the light to see if it goes back on. and no i did not take out the bulb.

:iagree:
well, read the code, and then clear it - at least you would not if the next time the light comes on for the same problem you cleared or for something else... and besides, it will give you food for thought, to think about what could have set off the code in the first place...

Lets clear up wha the point of the SES is. Its an indicator that something bad happened to your car. It could be any one of a number of things, 90% of which are emissions related. However, since emissions are affected by 90% of the components of the car, it stands to reason that its going to catch most anything.

What has to happen is that the computer has to see a fault occur (lets use a mis-fire), it has to happen more than once per driving cycle, or it has to be a major fault. If not, it simply stores the code as a shadow code (pending) until it hits the parameters to trigger. (02 sensors may be a fault within 4 trips, vac leak every 2 trips, etc...).

ok - the light has lit. now what. read the code, clear the code. If it comes back right away, you have a problem you need to address. If you clear it and it doesnt come back, it may have been a one time thing. But dont IGNORE the code.

common issue in the winter - P0128. Thermostat fails open. People ignore the warning. Then they freeze and car runs like crap.

or 02 sensors fail. System runs in closed loop mode, runs rich, gas goes down, power goes down, etc...

Check Engine light is your cars way of telling you it needs to see the doctor.

the good news is that you can review and clear the codes yourself.



PS - most of the auto parts stores will not read and clear codes anymore. My guess was that it was two fold 1) the liability of mis-diagnosing an issue and 2) they were getting pressure from the repair shops that they get 50+% of their business from to stop so customers would have to bring the cars in.

there may also have been inspection related issues as well.