chk engine light. why?

[bluntface]

Ok, i was driving from arizona to SD california today and my chk engine light comes on when im going up thru the mountins. im thinking its overheating but the temp gage didnt move, i pulled over chked the oil and radiator everything seems fine so i dunno what the problem is. i was driving fast.. like 90 witch is about 4000 rpms on the ti, and i was driving for a good 2 hours.. i dont want to wrek my car. can anyone help? why is the light on?

98 318ti 54000k

[newyorkm3]

Unless that check engine light is blinking...it's not an immediate critical issue. E36's are known to throw the CEL for very minute reasons. It could just be that your gas cap wasn't on snug, or the seal on it is going bad...or it could be a number of other things. Chances are it isn't a HUGE deal though. With that said, if it doesn't go away in a few days; have the CEL checked out to see what's up.

[bluntface]

that makes me feel better. i hope it turns off that whould be really cool, im used to that light being on forever on my other cars but all the others were POS.. thx man

[csk]

One of OBD's big jobs in life is to monitor your engine for emissions control purposes. The MIL (Malfunction Indicator Lamp aka. check engine) is supposed to come on when you have some malfunction that would cause any of your exhaust components[*] to rise above 150% of the legal limit. I'm told that many faults must show themselves on two consecutive driving cycles in order to light up the MIL, otherwise they just log a silent error into the diagnostic computer for your mechanic to fish out... Some faults can only be cleared with an OBD scanner, others will clear themselves after 5 error-free driving cycles.

As for WTF is actually wrong, if your car is a 96 or newer, get an OBD2 scanner. I have one of these scanners that I got on ebay. It's a tiny little thing that has a home in my glove box, and has come in handy many times... like the last time I didn't close my gas cap all the way.
[*] exhaust components like CO, NOx, SOx, unburned fuel or other volatile organics that the EPA doesn't want you pumping into the atmosphere...

[bluntface]

Originally Posted by csk

One of OBD's big jobs in life is to monitor your engine for emissions control purposes. The MIL (Malfunction Indicator Lamp aka. check engine) is supposed to come on when you have some malfunction that would cause any of your exhaust components to rise above 150% of the legal limit. I'm told that many faults must show themselves on two consecutive driving cycles in order to like up the MIL, otherwise they just log a silent error into the diagnostic computer for your mechanic to fish out... Some faults can only be cleared with an OBD scanner, others will clear themselves after 5 error-free driving cycles.

As for WTF is actually wrong, if your car is a 96 or newer, get an OBD2 scanner. I have one of these scanners that I got on ebay. It's a tiny little thing that has a home in my glove box, and has come in handy many times... like the last time I didn't close my gas cap all the way.

hey that is very interesting thanx for the info.. im ganna chk the scanners out

[BMWhartgeM3]

Originally Posted by csk

One of OBD's big jobs in life is to monitor your engine for emissions control purposes. The MIL (Malfunction Indicator Lamp aka. check engine) is supposed to come on when you have some malfunction that would cause any of your exhaust components[*] to rise above 150% of the legal limit. I'm told that many faults must show themselves on two consecutive driving cycles in order to light up the MIL, otherwise they just log a silent error into the diagnostic computer for your mechanic to fish out... Some faults can only be cleared with an OBD scanner, others will clear themselves after 5 error-free driving cycles.

As for WTF is actually wrong, if your car is a 96 or newer, get an OBD2 scanner. I have one of these scanners that I got on ebay. It's a tiny little thing that has a home in my glove box, and has come in handy many times... like the last time I didn't close my gas cap all the way.
[*] exhaust components like CO, NOx, SOx, unburned fuel or other volatile organics that the EPA doesn't want you pumping into the atmosphere...

very good post. dead on!

[hammerfang]

interesting, i might get one of those scananers

[delatlanta1281]

Does the pedal pump in on position not work on the ti's? On mine when my o2 sensor went I pumped the pedal a coulple times and it gave me a blink code.... that doesn't work for obd2?

[csk]

Originally Posted by delatlanta1281

Does the pedal pump in on position not work on the ti's? On mine when my o2 sensor went I pumped the pedal a coulple times and it gave me a blink code.... that doesn't work for obd2?

Nope. The pedal pumps only works for OBD1 (pre '96). The list of quantities measured is much smaller and more coarse making it somewhat reasonable to read the measurements out with blinky lights.

I'd have to do a some digging to find out for sure how many there are, but there are apparently over 200 sensors reporting to OBD2, and at least 470 generic powertrain codes in OBD2 - I only have definitions for 472 of them. The generic codes are the ones all manufacturers use and they mean the same thing. There are also vendor codes. Generic code P0170 (Fuel Trim Malfunction - Bank 1) could be further explained by any of 9 more specific BMW codes. I have definitions for another 500 BMW powertrain codes...

Besides powertrain (intake, fuel management, combustion and exhaust) OBD2 monitors many more things, but a) they don't tend to light up the MIL, and b) some cheap scanners will only pull the powertrain codes. The cheap one I got on ebay will pull both the generic and the vendor codes, but it only includes explanations for the generic codes.

For those who don't know how to read OBD1 codes - http://www.bimmerzone.com/fcodes.htm