.:: Question about check engine light

Syn · 03-01-2011, 02:36 AM

Hello all,

Looking to purchase a 2001 330i and when I went to see the vehicle it was in very good condition but the check engine light was on, asked the owner how long thats been there and he said his wife put 87 octane gas (regular) in the vehicle and because of not fueling with premium unleaded gas that the engine light came on. He said he had a scanner and could show me that it was just "low octane emission".

Spoke to him 2 days later and the check engine light is off.

Is this true with BMW's? I thought it was only with turbo vehicles.

Sorry for the newbie question, and thank you in advance.

propr'one · 03-01-2011, 05:27 AM

What he said is possible but not very likely. An OBD2 code scanner is like 30$, worth the investment if you're going to buy a used car.

dcramer · 03-01-2011, 08:09 AM

Sounds pretty suspicious to me.... I'd walk unless it's a really good deal.

BimmerGuys · 03-01-2011, 09:01 AM

"low octane emission" no scanner can tell you that

arsevader · 03-01-2011, 10:00 AM

Won't pass emissions with a check engine light on anyway so you won't be able to get plates until it's sorted out. Be suspicious.

tg07lq · 03-01-2011, 10:09 AM

^ check engine light doesnt have any effect on safety/etest. i had mine on for both, not even mention of it.

Syn · 03-01-2011, 11:34 AM

Quote:

Originally Posted by propr'one

What he said is possible but not very likely. An OBD2 code scanner is like 30$, worth the investment if you're going to buy a used car.

Can check engine light happen in a BMW if correct gas is not used?

Renboy · 03-01-2011, 11:42 AM

Quote:

Originally Posted by tg07lq

^ check engine light doesnt have any effect on safety/etest. i had mine on for both, not even mention of it.

Legally a shop is not allowed to do an etest on a vehicle with a CEL on. CEL comes on for emissions related problems and it WILL NOT be triggered by running 87 octane. I run that gas all winter long and never a CEL.

When you go look at the car again, go for a long test drive and see if the CEL comes back on. Given his 'octane' explanation I'd be pretty suspicious, and it wouldn't surprise me if he turned the CEL off with a scanner before you got there.

Syn · 03-01-2011, 12:10 PM

Quote:

Originally Posted by Renboy

Legally a shop is not allowed to do an etest on a vehicle with a CEL on. CEL comes on for emissions related problems and it WILL NOT be triggered by running 87 octane. I run that gas all winter long and never a CEL.

When you go look at the car again, go for a long test drive and see if the CEL comes back on. Given his 'octane' explanation I'd be pretty suspicious, and it wouldn't surprise me if he turned the CEL off with a scanner before you got there.

Yea I would def go for a test, and he did say he had a scanner so possibility of him turning it off is def there. He is an older guy and seems straight forward but I don't want to spend major $$ on repairs after purchasing a bmw

arsevader · 03-01-2011, 12:27 PM

Quote:

Originally Posted by Syn

Yea I would def go for a test, and he did say he had a scanner so possibility of him turning it off is def there. He is an older guy and seems straight forward but I don't want to spend major $$ on repairs after purchasing a bmw

Turning it off actually doesn't get rid of the code in the system. There is a specific cycle of driving test that have to happen before the code actually is removed so it's possible to find out what the issue was.

The thing is, why is he selling a car with a light on to begin with. If it was such a minor thing then why not wait till the 'gas issue' resolved itself before listing it?

I hear this all the time, 'oh it's nothing, easy to fix'. If so why not just fix it then?

Syn · 03-01-2011, 12:49 PM

Quote:

Originally Posted by arsevader

Turning it off actually doesn't get rid of the code in the system. There is a specific cycle of driving test that have to happen before the code actually is removed so it's possible to find out what the issue was.

The thing is, why is he selling a car with a light on to begin with. If it was such a minor thing then why not wait till the 'gas issue' resolved itself before listing it?

I hear this all the time, 'oh it's nothing, easy to fix'. If so why not just fix it then?

he said it happened that morning, because I gave him 24hrs notice that I would be there to look at the vehicle, his wife drives the car and put the wrong gas in it (his story) and then I went over to see it and asked him about it, now the light is gone as its been refilled with premium unleaded.

its going in for inspection, I mentioned it to a mechanic - we will see what happens

Renboy · 03-01-2011, 12:59 PM

Just the opposite James, turning it off with a reader/scanner does get rid of codes stored, repairing the problem and having the light go out on it's own doesn't clear stored codes.

Either way, if it's a significant problem the light will go on soon after start up (if not immediately), however, just because a problem is significant in terms of engine operation doesn't mean it's expensive. A crank sensor is relatively cheap and easy to fix, but will stall out an engine. A faulty cat (exhaust manifold) will have no noticeable effects on driveability (unless it's completely plugged up) but costs a fortune to replace.

Tread carefully.

arsevader · 03-01-2011, 01:31 PM

Quote:

Originally Posted by Renboy

Just the opposite James, turning it off with a reader/scanner does get rid of codes stored, repairing the problem and having the light go out on it's own doesn't clear stored codes.

Hey Man,

Actually....

Just clearing the codes with a scanner doesn't actually remove them from the system. If that was the case then everyone could just clear codes before getting state inspections (which in some states are more thorough). They can tell if the code has been cleared.

You can clear the codes and turn off the light with tools such as Peake tools etc. However the actual error is stored until the the predetermined cycle has been completed. No scanner/reset tool can remove this stored code.

http://www.europeantransmission.com/...0Procedure.pdf

mamadci · 03-01-2011, 03:13 PM

this is exactly what previous owner told me when i bought my car off him. CEL was on and he told me its because he used 87 octane fuel. back then i didn't know shit about bimmers so I believed the guy. later i found out it was because of bad valve cover gasket cause it was leaking. After i replaced the VCG i never got CEL up to this date. so be careful when buying a used bimmer.

Renboy · 03-01-2011, 11:11 PM

I believe you misread your pdf. Page 4, #6:
The fault code will also be cleared from memory automatically if the specific function is checked through 40 consecutive drive cycles without the fault being detected OR with the use of either the DIS, MODIC or Scan tool.

I have a bunch of scan tools, and if I clear codes with any of them, the others won't pick them up, the codes are gone. I have had numerous instances where codes popped up that didn't trigger a CEL so I assumed they were there until manually cleared. I didn't know they would eventually clear themselves.

If you would like to settle this, when I come down there or you're up here, I'll run my car with a disconnected maf, then clear the code with any one of my 3 scanners, and then try to read the codes with either of the other two. I'll give you the benefit of choosing which scanners will be used

Quote:

Originally Posted by arsevader

Hey Man,

Actually....

Just clearing the codes with a scanner doesn't actually remove them from the system. If that was the case then everyone could just clear codes before getting state inspections (which in some states are more thorough). They can tell if the code has been cleared.

You can clear the codes and turn off the light with tools such as Peake tools etc. However the actual error is stored until the the predetermined cycle has been completed. No scanner/reset tool can remove this stored code.

http://www.europeantransmission.com/...0Procedure.pdf