'06 GMC 3/4 ton van

Check engine light on. Company mech said O2 sensor(s). replaced sensors. Light off for about a day. Rechecked replaced other O2 sensors (up and down stream).
Light off about a day again.

I suppose I refueled before the light lit but, after the sensor change.

Sent van to dealership. Dealer had it 6 days. Got it back last night. 3/8 tank of gas. home and back and some running this morning no light. Back to the shop around noon to fill up. after fill up check engine light is back on.

Between sensor changes i mentioned to the mechanics that if i get low on fuel ( before the warning light comes on) the ck eng light goes out. Upon filling up it "relights".

Any ideas. Its a work van for a heating company and its busy now and I cant do much in a spare van with few parts or tools other than hand tools.

thanks
Ed

 

Since it's going hand in hand with filling the gas tank, I would say gas cap, then evap system. The gas cap first because it's cheapest.

Hope this helps,

Bob

 

On any of the reciepts, does it say what diagnostic trouble codes (DTC's) were set? If they were indeed O2 sensor codes, filling up will have nothing to do with it.

How many miles are on the van?

 

28000 miles
dont know what the codes were.
after resetting the system the light would stay out untill the first full tanks of gas.

In august the van was nearly totaled. squashed between a minivan (on left) and guard rail (on right) and the car that started the wreck on the front. all cosmetic. perhaps something came loose. never drove it again till October. As I recall the light came on when I first filled it up later that day.

Our shop guy said its because I had the truck runnin' while refueling. Im not buying that. He also said it will reset it self after several starts.

The light did go out after the last fill up (engine off ) but relit after a few miles of driving.

 

Bring it by a Autozone and they will scan the codes for free. Once you get the codes, report back here.

Luckily all this is under warranty?

 

yep if its still under warranty why would you mess with it , just take it back to dealership , let them handle it