Check engine light is on but car is running fine

[bobbyt454]

Hi all,
My check engine light came on this morning on my way to work but the car is running fine. Any thoughts? I didn't give it ample time to warm up this morning, and the computer thinks the oil hasn't been changed in quite some time (I don't have the reset tool) but in reality it's been changed every 5k.
Just listing a couple things that may or may not be related.
Is there a way to get a read out on what the malfunction is?
Thanks!

[1997328IS]

Take it to Advance Auto/ Pepboys, or whatever you have locally to get the code read. May or may not show everything you need to know about it.

All you need is a paperclip to reset your inspection lights. Do a quick google search for it.

[kalinrs]

The check engine is on on my 525i due to a breather valve. It has run fine for over 6 months now because I am too cheap to replace a $80 part the size of an egg :). I don't think a small magnetic valve should cost $80 either.

So it could be a lot of things - most likely something stupid like that since the car still runs fine.

[bobbyt454]

Thanks for the tips guys. I'll head over to advance on my lunch and try to paper clip reset!

[paniolo]

Yeah, the check engine light primarily tests emissions control systems, not the overall state of engine. Though sometimes it can indicate a sensor failure that does impact drivability, quite often you don't really notice anything. As said, hit up a local parts store and ask them to read the codes. Every one I've been to does it for free to try and sell the parts.

[TCarlisle]

I always suggest people buy their own OBD-II code reader. Yes, you can get codes read free at some chain auto stores, but how feasible is it to run to have the codes read anytime you want to troubleshoot or diagnose?

A basic code reader is well under $100 and will pay for itself in quick time by giving you the visibility you need into the OBD-II system to make quick, accurate diagnostics instead of throwing random parts at the problem.

And no, I am not a code reader salesguy.... :D

[bobbyt454]

Hi all,
A) The inspection display cleared just as you said with the paper clips :), thanks again!
B)Just got back from the autozone and the read out was "insufficient coolant temperature for closed loop fuel control". My first instinct is that the t-stat might be stuck open or beginning to fail as my engine temp is running a little cooler than usual. Thoughts?
Thanks again!

QUICK UPDATE!
I turned the key from on to off three times to clear the check engine light. When I started the car the light was gone. I did this assuming that if it was just a hiccup or glitch that it would clear and not return, and if it was a real issue it would return when it achieved it's operating temp. Is this assumption correct?
I drove it for about 15 minutes (highway and city). The light never came back on and the car is running at normal operating temperature.
Should I be concerned that I still have an issue or will the check engine light return if the problem persists?
Thanks again!

[medic1dl]

Clearing the code does not fix the initial problem. If the problem is still there the CEL will come back on. There are (I'm pretty sure) 2 temp sensors. One for the temp gauge and one for the computer. If the code was that the temp of the engine was too low for closed loop then that temp sensor is probably faulty. If this is so, your car will be running in open loop all the time and this will significantly hurt your gas mileage. There are ways to test the sensor. I say do it and see if the sensor needs to be changed.

[bobbyt454]

I have noticed that my gas mileage has gotten a little worse lately. I thought I was driving with a heavier foot. Any tips on how to check it?
Thanks!

[medic1dl]

Just look in the Bentley's manual. There is a way to test it and it will show you how to do it.

If you don't have the manual do a search on the forum for it there is a link to it.

[flyfishvt]

Just giving my backing to the sensor causing your problem. medic1dl's logic on this is spot on.

[ThaiRacer]

Lol at the thread. Sometimes e36 owners have no common sense. I mean a check engine light comes on and u rather post a thread then have some1 diagnose the code. Then rather fixing it u reset the computer thinking the car will fix itself lol.

[bobbyt454]

Hey Thai Racer,
I never thought it would fix itself. I've been working on cars for twenty years and am new to the e36. I thought it may have been a hiccup, and I wanted to be sure that the check engine light would return if it WASN'T and if it was an actual problem.
I appreciate everyones help as I am new to the bmw world and am working my way throughout but I'm sure NO ONE appreciates your type of post. If you read through the posts you'd know I first posted regarding HOW TO get a read from the check engine sensor and then the appropriate steps to take after, regarding this specific issue.
This is a forum for people to help each other, not to berate, and if you COULD READ then you'd know exactly what I was asking, but I'll consider your hasty ill-informed post to be a sign of your illiteracy and poor education.
Thank you to everyone who has helped and contributed positive feedback and support.

[ThaiRacer]

Working on cars for 20 years? Common sense would have told u to take your car to get it scan. Then u fix the issue. Simple as that. It doesn't matter BMW or Honda if a code comes up something is wrong rather it be big or litle.

[bobbyt454]

Hi all,
I replaced the coolant temp. sensor and while my gas mileage has gone back to normal (if not better) the check engine light is still on and throwing the same code. The car will eventually reach it's normal operating temperature at 12 o'clock and I am getting heat from the vents so I'm not sure that it's the thermostat failing or stuck open and my coolant is at the proper cold level. Any other suggestions for what to look for? It's about 20 degrees here right now but I can't imagine that it being cold outside would keep the coolant from reaching it's standard operating temperature.

[Crime Wave]

I wish I had OBDI; much easier to diagnose.

[flyfishvt]

I still say its the tstat. Its very possible its not closing completely. This would cause it to take longer to warm up. That's exactly what that code is telling you. The engine isn't getting to correct operating temp fast enough. At 20F it takes about 5-10 miles at 50mph for my 325 to get to full operating temp.

[lukee36]

Have you tried keying up (dont turn it over) and pumping the gas pedal a full 5 times, the CEL will read you a code. Look that code up online you should find your problem. Its a good trick but I think your car has to be pre-'96

[RNeil]

It sounds like the car is getting hot enough. Are you sure you replaced the right sensor. There are 2. The better scanners will tell the temperature the ECU thinks it is. Then you can see if it is resonable. Did you reset the CEL? Some faults take time before the CEL resets itself.

[bobbyt454]

Hi all,
Thanks for all the input here. I really appreciate it. On the '99's apparently there is only one coolant temp. sensor that feeds both the gauge and ECU. Still having the same problem and I haven't had a chance to swap out the T-Stat yet. Also, 2 more codes of popped up. P1188 and P1189 which are Bank 1 Sensor 1 and Bank 2 Sensor 1 codes. I think these refer to the 02 sensors before the cat (is that correct?). Could the car not running in closed loop mode cause an error at these sensors? The check engine light has been coming on and off (without me clearing it), turning on when it's very cold, an then turning off on warm days. I think I need to just replace the t-stat as flyfishvt said, but I wanted to run the other two codes by you guys first.
Thanks again!

[flyfishvt]

Check out some of the links in this search result.

http://search.mywebsearch.com/mywebsearch/GGmain.jhtml?searchfor=P1188+&tpr=sbt&st=bar&ptnrS=ZUxdm3995RUS&ptb=nL5hv0BMfFTXvyiJFIvaVQ&ss=sub&gcht=&n=77d00207&ps=P1188+check+engine+light


all of them say its a Fuel/Air mix problem. In other words you have air that is leaking into the system and not going through the MAF. At the very least you need to check all the connections between the MAF and the throttle body. Chances are you have a crack in the tubing or a loose connection. There are other causes discussed in some of these but it all comes down to the same thing. Unmetered air is getting in somewhere. Its also possible that a faulty Pre Cat O2 sensor could cause this but that's probably not the case with your car since you are getting 1188 and 1189 codes. That indicates to me that the problem is on the intake side.

[ChuckDizzle]

Thanks for the tips guys. I'll head over to advance on my lunch and try to paper clip reset!

when was the last time you filled up your gas tank. Air in the gas tank will set off the CEL. Doesn't do anything, but the computer just doesn't like the reading. I'd still get the codes scanned to be sure.

[sunbrn]

when was the last time you filled up your gas tank. Air in the gas tank will set off the CEL. Doesn't do anything, but the computer just doesn't like the reading.

really? and you read this where?

[ChuckDizzle]

really? and you read this where?

Experience, not reading and speculation. More common with e46s but has been known to happen with the e36. Comes up as a fuel bank error

[bobbyt454]

That makes perfect sense. Part of the intake hose directly behind the MAF is cracked. I had to take the tape off when I was replacing the coolant temp. sensor and my guess is that I didn't close the crack up all the way when I was done. Thanks again. Next stop T-Stat. Oh, also the attendant at the auto parts store said that I could be throwing the insufficient coolant temp for closed loop op. code because my water pump may be malfunctioning, in that the fins may have separated and not be delivering the fluids during idle. Any thoughts?
Thanks again!

P.s. I got gas just two days ago. I'll check that hose and then take it from there. Will that air eventually work it's way out of the gas tank?

[sunbrn]

Experience, not reading and speculation. More common with e46s but has been known to happen with the e36. Comes up as a fuel bank error
I could see with a loose or faulty gas cap causing this but not a half empty gas tank. Millions of people run their tanks low all the time and I don't see this as a rampant problem. But then again I have been known to be wrong once before.

[ChuckDizzle]

I could see with a loose or faulty gas cap causing this but not a half empty gas tank. Millions of people run their tanks low all the time and I don't see this as a rampant problem. But then again I have been known to be wrong once before.

No, not cause you have a 1/2 tank.

Its when air enters the gas tank when you're filling up. The gas tank is sensitive as are the sensors (the e36 is just a touchy and emotional bitch overall). Its got nothing to do with fuel level

[sunbrn]

That makes perfect sense. Part of the intake hose directly behind the MAF is cracked. I had to take the tape off when I was replacing the coolant temp. sensor and my guess is that I didn't close the crack up all the way when I was done.
But didn't you have the fault BEFORE you even started working on it when you removed the tape?

[ChuckDizzle]

P.s. I got gas just two days ago. I'll check that hose and then take it from there. Will that air eventually work it's way out of the gas tank?

Yes

[bobbyt454]

Real quick question that I'm sure you guys know the answer to. How many miles of driving does it take for the ECU to run a full diagnostic loop (and what type of driving). I can't seem to find the answer on here, maybe I'm looking for the wrong thing. But I fixed a leak inbetween the MAF and the throttle body and I'd like to run a full loop so I can see if the sensor 1 codes will go away.
Thanks again for all your help! I'll be changing the T-Stat out next week and will be sure to let you know how it goes!

@ sunbrn: I had the insufficient coolant temp codes, but not the sensor 1 codes. They came up after I replaced the coolant temp sensor and to do so I had to move the intake bellow and remove the tape closing the crack, which I admittably did not do a great job of retaping when I was done the job.

[sunbrn]

Mine took about 100 miles or so to return with a CEL.

[bobbyt454]

Hey guys,
Just wanted to say thanks again for all your help! This weekend I replaced the t-stat (and housing), flushed and changed the coolant and the car is back to normal. The check engine light went off too (I'm going to have it scanned tomorrow to be sure but so far so good). Only about two gallons of coolant drained out, and it only took about two gallons to fill it. I did some substantial bleeding and massaging of hoses so I'm thinking maybe not all of the coolant drained out initially. I'm going to check the coolant level tomorrow morning to be sure but I drove it about 30 miles afterward on the highway at around 80mph and there was no sign of overheating at all.
Thanks again for all your help and guidance you guys were totally clutch! Hopefully someday when I'm not a complete newb I can return the favor.
Cheers!
Bob