Check Engine Light
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Joined: Jun 2002
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From: Marquette MI
Check Engine Light
My 2002 C5 has for years given me problems with a recurring Check Engine Light. I get frequent dx codes indicating problems with O2 sensors. I recently had the offending O2 sensors replaced. I then filled up the gas tank and within 10 miles the Check Engine Light came on. When I checked the dx codes I had at least 15 different codes from many sources in addition to the PCM. Then it occurred to me that the CEL comes on after fill ups and that when the car was relatively new I experienced my first CEL which was supposedly caused by a faulty gas cap, In my memory [some times faulty] replacing the cap solved the problem for a while. Does this make any sense? I do not recall any dx codes indicating a faulty gas cap. I really would like to get rid of the recurring CEL. Advice?
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Joined: Sep 2013
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From: Cape Coral, Florida
Let us know what codes you do have accessing them through the DIC...post them up and we can possibly help...if you don’t know how to do that you kind find the procedure on the Forum !!...if your CEL is due to some EVAP issue best left to a pro who has the right diagnostic equipment !!
Last edited by C5 Diag; Sep 16, 2019 at 12:54 PM.
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Joined: Sep 2013
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From: Cape Coral, Florida
The Evaporative Emission System keeps fuel vapors from escaping from the fuel tank into the atmosphere ...it’s been around since the 70’s !!...great instructional video below so grab a couple beers and enjoy!!....there will be a 50 question quiz at the end...LOL !!
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Joined: Jun 2002
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From: Marquette MI
Just finished the video C5 Diag sent. Very informative! I was especially intrigued by the purge solenoid's effect on the bleed up rate when the DVOM decreases while back probing the purge with the front and back door opening and closing. And all this happened without a CEL!
Seriously - this is way out of my league but my mechanic did say something about an evaporation canister.
Thanks C5 Diag.
Seriously - this is way out of my league but my mechanic did say something about an evaporation canister.
Thanks C5 Diag.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,495
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From: Cape Coral, Florida
Bob, you passed the test !!...LOL !!...let us know what your mechanic finds !!...what code do you have BTW ??...maybe something simple to save you a trip to your mechanic !!
Last edited by C5 Diag; Sep 18, 2019 at 10:01 AM.
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Thread Starter
Pro
Joined: Jun 2002
Posts: 726
Likes: 45
From: Marquette MI
My last CEL was due to dx codes PO137 and 157 which relate to O2 sensors which were just replaced.
When i told my mechanic about my latest symptoms he confirmed the codes but also asked me if I topped off my gas tank after the pump automatically shuts off. I always do that just to get the gas charge to an even dollar. He suggested that might be causing the CEL - so I will quit doing that and see what happens.
Thanks for humoring me.
When i told my mechanic about my latest symptoms he confirmed the codes but also asked me if I topped off my gas tank after the pump automatically shuts off. I always do that just to get the gas charge to an even dollar. He suggested that might be causing the CEL - so I will quit doing that and see what happens.
Thanks for humoring me.
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Joined: Sep 2013
Posts: 15,495
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From: Cape Coral, Florida
Are you saying you are still getting the 0137/0157 after the O2 sensors had been replaced ??...those DTC's are for the rear O2 sensors seeing a "lean" condition and if you are still getting those 2 the car was not properly diagnosed !!... Those have nothing to do with filling up your tank past shut off if that is what you are saying...if you overfill you can possibly get raw fuel instead of fuel vapors into your EVAP charcoal canister but I shouldn't have to tell you this...LOL !!...oh, BTW if your purge valve WERE stuck open after fill up you would have a rich condition (fuel vapors getting drawn into the intake manifold) followed by a LEAN condition after the fuel vapors have been used up but I would think you would get 2 lean codes for your front O2 sensors too !!
Last edited by C5 Diag; Sep 18, 2019 at 11:28 AM.
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Joined: Jun 2002
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From: Marquette MI
We know those codes are for the rear 02s. I have long tube headers on the car and we are going to recheck the connections on the rear sensors. There seem to be lots of possible variables that trigger my current CELs.
It's a beautiful fall day here in Upper Michigan so I am going to put the top down and enjoy Lake Superior hopefully without seeing any CELs.
Thanks for your input.
It's a beautiful fall day here in Upper Michigan so I am going to put the top down and enjoy Lake Superior hopefully without seeing any CELs.
Thanks for your input.
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Joined: Sep 2013
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From: Cape Coral, Florida
Yes, check connections !!...I know many have O2 issues after installation of long tubes...were they a recent addition ??...any exhaust leak downstream of the front O2’s up to the rear O2’s can cause a lean condition in the rear O2’s !!...there may also be wiring issues which I hope your mechanic will look at !!...have a fun drive !!...you can clear the codes....go for a drive and before shutting the car off see which DTC’s may have come back !!
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Joined: Jun 2002
Posts: 726
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From: Marquette MI
Had my exhaust guy look for leaks . He found some "Spider web" cracks that he filled at the rear end of the headers. Took the car for a ride today and got another CEL with dx codes of 0133 and 0153. So guess it was not an exhaust leak. Any other suggestions?
