Bad gas cause CEL?

[Lyman]

So one of my sons bought a used GMC Canyon 3.5 I5 a week ago. He had to put gas in it the same day he bought it. Truck was fine for the first 100 or so miles. About 50 miles after the fuel stop the CEL lit. He has a code reader and said it was Lean fuel mixture bank 1. I figured it might be the gas cap or MAF or maybe a loose vacuum line. Before we could meet up to start a diagnoses he needed gas again and filled up. The CEL went out and has been out for the last 80 miles. He had checked the gas cap right after the CEL first lit and said it looked fine and was tight.
So my question for you guys is could low grade fuel trigger a CEL for one tank of fuel or do you think it is something else? I have heard of this happening but never seen it happen myself.

 

[eljefino]

My first consideration would be that it was somehow rigged up to (barely) pass smog. Though maybe you got a load of fuel with more than 10% ethanol.

 

[Lyman]

In CA it would be pretty hard to rig anything to pass smog. It's a very thorough test. Truck had an independent prepurchase inspection too. It's a very clean one owner truck with full history.

 

[mattwithcats]

Old gas caused a P0341 code for me...

Red bottle of Heet, and half a tank of fresh gas, reset the code, has not come back...

 

[01rangerxl]

Could be.

My truck is flex fuel. Ethanol is hygroscopic. Once in a while, I get a tank of E85 that triggers a lean code, either on one or both banks. Top off with regular gas or E85 from somewhere else, and it goes away. Never happens with regular gas, and has only happened with ethanol from one station, but it has occurred with ethanol from that one station multiple times. I think in those cases I'm getting watery ethanol.

If the light stays off, write it off as bad gas. If there is an underlying issue, the CEL will be back soon enough.

 

[Lyman]

My Son wanted to clean the MAF today and I told him that we should hold off so we wouldn't be changing anything. I want to wait it out for a week or two and see if the CEL comes back or not. He normally buys Chevron gas at the same station. The first tank was from an independent station.

 

[The_Eric]

Check the breather hose. Relatively common issue on these.

 

[Lyman]

Originally Posted By: The_Eric
Check the breather hose. Relatively common issue on these.
Thanks. I will.

 

[zzyzzx]

What code did you get when you checked?

 

[Lyman]

PO171