Three years running. when the gas tank sees about 60F, check engine light

drvrd · Jan 21, 2021

When weather gets cool enough ~60F going down my check engine light comes on, also goes off when temperatures are >60F. One can of STP water chase, STP injector cleaner or Techron makes the light go off until the next fill-up or two. She is a 2004 SLT Yukon and has 212K miles on her. A winter of STP water chase, STP injector cleaner or Techron per tank fill or two can get expensive.

Been told this is a fuel filter issue, does anybody concur? Any other suggestions?

Thanks in advance for your thoughts.

DrvrDon

Fless · Jan 21, 2021

Welcome to TYF.

I can't say if the problem is caused by a fuel filter issue, but if your truck is Flex Fuel there should be a fuel filter on the left frame rail. If it hasn't been changed lately, it would be a good idea to replace it.

When the check engine light comes on, what code is setting it? Bet it's an emissions code since the tank may be depressurizing when the fuel cools.

wjburken · Jan 21, 2021

Welcome to the forum from Iowa.

As mentioned already, figure out what code the vehicle is throwing next time the check engine light comes on. If you don’t have a reader, you local Autozone can get you the code for free. Just don’t blindly follow their scripted response as they want to sell parts and many don’t care if it actually solves the problem. That code is the first clue you need as it lets you know what the vehicle is erroring out on.

Joseph Garcia · Jan 22, 2021

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics, please.

You have already received some initial feedback and suggestions, and other folks will chime in. As @wjburken stated, obtaining the code that is being thrown when the check engine light comes on will be the fastest and most accurate place to start in the diagnosis and resolution of this issue. We can provide more definitive assistance, once we know what code is being thrown.

Doubeleive · Jan 22, 2021

unless you are getting a mis-fire most check engine light causes are emissions related, fuel additives really shouldn't be fixing the issue and it may just be coincidence, if it is a code related to the fuel system like a vacuum leak, faulty solenoid, bad vapor canister, then the act of simply refueling and opening and closing the gas cap could be correcting the issue briefly.
We need that code to assist further, next time it comes on go get it scanned and report back.

drvrd · Jan 25, 2021

Thanks for everybody's comments.

The pattern I describe is very consistent for more than three running years, and persistent. I refueled half a tank refill yesterday while temperatures were in the Mid-60s. Had a check engine light from the half tank before adding half more refill when the check engine light went out afterward. PS same COSTCO fill source in all these cases. So no code possible until there is a temperature drop, unless the code detect has a history file capability. The station's in ground fuel tank has to be below 65F. Last year saw it come on immediately after refilling a low tank from a QT station.

I bought this 04 Yukon SLT used with 113K, and do not see indication of flex fuel capability (where can I check), but does have a fuel filter mounted on the frame rail about under the drivers seat.

Do the fuel cap seals have any history of age failure?

Fless · Jan 25, 2021

@drvrd Flex Fuel vehicles have a "Z" as the 8th VIN digit. What's yours?

And on a Flex truck there is a small E85 sticker inside the fuel door.

Unless it's been changed the fuel filler cap should be yellow. Any fuel cap can go bad; I've had to change mine due to it failing a seal test during an emissions inspection.

Doubeleive · Jan 25, 2021

drvrd said:
Thanks for everybody's comments.

The pattern I describe is very consistent for more than three running years, and persistent. I refueled half a tank refill yesterday while temperatures were in the Mid-60s. Had a check engine light from the half tank before adding half more refill when the check engine light went out afterward. PS same COSTCO fill source in all these cases. So no code possible until there is a temperature drop, unless the code detect has a history file capability. The station's in ground fuel tank has to be below 65F. Last year saw it come on immediately after refilling a low tank from a QT station.

I bought this 04 Yukon SLT used with 113K, and do not see indication of flex fuel capability (where can I check), but does have a fuel filter mounted on the frame rail about under the drivers seat.

Do the fuel cap seals have any history of age failure?

yes check engine lights will stay as a history code, from what I have read some may go away after XX amount of restarts, others like abs or airbag may not stay as history codes.

drvrd · Jan 26, 2021

Fless said:
@drvrd Flex Fuel vehicles have a "Z" as the 8th VIN digit. What's yours?

And on a Flex truck there is a small E85 sticker inside the fuel door.

Unless it's been changed the fuel filler cap should be yellow. Any fuel cap can go bad; I've had to change mine due to it failing a seal test during an emissions inspection.

Yes 8th vin number is a Z, but fuel cap is black.

Doubeleive · Jan 26, 2021

ya there are some vin z that are not flex fuel I have one

Three years running. when the gas tank sees about 60F, check engine light

drvrd

TYF Newbie

Fless

wjburken

Joseph Garcia

Doubeleive

Wes

drvrd

TYF Newbie

Fless

Doubeleive

Wes

drvrd

TYF Newbie

Doubeleive

Wes

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