Check engine light- engine electronics stupid reason(gas cap open)?

6.3 · 04-22-2003, 11:14 AM

Well you think that it would never happen to you but I was a little absent minded yesterday and after I got fuel I forgat to close the gas cap on my 98 e430.
My niece noticed it and just closed the door without telling me. Later like a half hour all of the sudden the check engine light comes on and I am like what the hell! in the middle of park ave in Manhattan. The car runs perfect though. A little puzzeled my girlfriend just threw an idea If I closed the gas cap. I would never think of that being the problem.
I opened the gas cap door and the cap was nicely tucked inthe holder but not on the hole. After I closed it I decided to complete the 70mile jurney I had ahaed of me and today the check engine light was gone.
Can someone tell me why would this trigger the check engine error?
Unless this is not related should I go have it checked out.
The error is now gone and the car runs like it did. Perfect!

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Turbo][ · 04-22-2003, 01:15 PM

because of the cap being open, the fuel pump isn't able to keep a steady level of volume pressure for the fuel injectors. The car has a Fuel Pressure sensor

mbtech208 · 04-23-2003, 12:20 AM

It's an emissions reason. By leaving the gas cap open, you're allowing fuel vapors to escape into the atmosphere instead of collecting in the charcoal canister, a huge no-no.

E-Klasse · 04-23-2003, 02:38 PM

A lot of repair shops have made a lot of money off of that same fault. The gas cap seal is an emission standard to check for and will flag the CE light until the fault is corrected. A shop will tell you that your MAF (mass air flow) sensor is bad and charge you $400 to swap it and then replace the gasket on the gas cap. After driving for about 50 miles the code will clear or they clear it with a OBDII code scanner. Thank your girl friend for thinking of the gas cap...

6.3 · 04-23-2003, 02:55 PM

Yeah I did thank her

But also thought what a cool way for dealers to make money. After I realised that the open cap was probably a problem I drove again and the code cleared by next morning.
thanks

mbtech208 · 04-23-2003, 09:25 PM

Quote:

Originally posted by E-Klasse
A shop will tell you that your MAF (mass air flow) sensor is bad and charge you $400 to swap it and then replace the gasket on the gas cap

I'd never go to that shop again. If I get a car in with a Check Engine light on and it turns out they left the gas cap loose, I'll tighten the cap and clear the code, no charge. Next time it happens though, that's when I start charging labor for their absent-mindedness.

michakaveli · 04-23-2003, 11:10 PM

Quote:

Originally posted by E-Klasse
A lot of repair shops have made a lot of money off of that same fault. The gas cap seal is an emission standard to check for and will flag the CE light until the fault is corrected. A shop will tell you that your MAF (mass air flow) sensor is bad and charge you $400 to swap it and then replace the gasket on the gas cap. After driving for about 50 miles the code will clear or they clear it with a OBDII code scanner. Thank your girl friend for thinking of the gas cap...

I had that this past winter in my dies... Mind you it was 15-18 degrees Farenheit :-) After about 100 miles the "check engine" went......

04-23-2003, 12:20 AM	#3
mbtech208 MBWorld Fanatic! Garage is empty, add now Join Date: Nov 2001 Location: Bloomington, IN Posts: 2,332 Drives: 1997 Toyota Tacoma 4x4	It's an emissions reason. By leaving the gas cap open, you're allowing fuel vapors to escape into the atmosphere instead of collecting in the charcoal canister, a huge no-no. __________________ Dave ASE Master Technician

04-23-2003, 02:38 PM	#4
E-Klasse MBWorld Fanatic! Garage is empty, add now Join Date: Mar 2002 Location: Arizona, USA Posts: 1,497 Drives: E-Class W210, SLK R170, Jetta MKV TDI, MINI Cooper S	Thank you girl friend A lot of repair shops have made a lot of money off of that same fault. The gas cap seal is an emission standard to check for and will flag the CE light until the fault is corrected. A shop will tell you that your MAF (mass air flow) sensor is bad and charge you $400 to swap it and then replace the gasket on the gas cap. After driving for about 50 miles the code will clear or they clear it with a OBDII code scanner. Thank your girl friend for thinking of the gas cap... __________________ I assume no liability for any incidental, consequential or other liability from the use of this information. All risks and damages, incidental or otherwise, arising from the use or misuse of the information contained herein are entirely the responsibility of the user. Although careful precaution has been taken in the preparation of this information, I assume no responsibility for omissions or errors.

04-23-2003, 02:55 PM	#5
6.3 Member Garage is empty, add now Join Date: Sep 2002 Location: NY Posts: 230 Drives: 2003 s500 sport	Yeah I did thank her But also thought what a cool way for dealers to make money. After I realised that the open cap was probably a problem I drove again and the code cleared by next morning. thanks __________________ 2003 S500 SPORT

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04-22-2003, 01:15 PM	#2
Turbo][ Senior Member Garage is empty, add now Join Date: Nov 2001 Location: So.Cal Posts: 342 Drives: 98 E430	because of the cap being open, the fuel pump isn't able to keep a steady level of volume pressure for the fuel injectors. The car has a Fuel Pressure sensor

04-23-2003, 11:10 PM
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