CEL after filling gas tank completely?
 

Hey peeps,

So as of Sunday, my CEL for my P770 code magically disappeared on a chilly day, cool. I have been driving back and forth since, about 120 miles over two days. I stopped for gas, filled my tank completely, and topped it off once it clicked. As soon as I get in WHAM, CEL comes back up.

Originally this CEL has been driving my mechanic up the wall. They changed the shift solenoids, filter, TPS, and even changed the onboard computer (not the ECU, the one behind the glove compartment) and still nothing. They cleared code, I bit the bullet and drove off with it, only for a few days for it to come back again.

I have driven the car for a couple of weeks now, no issues at all just the annoying CEL staring back at me. A chilly on Sunday, come today I pull into the gas station after work, fill my tank and suddenly it's back.

Now I'm not saying it has something to do with my fuel system... but is there a chance that something else can go on that is tripping that code? It just boggles my mind that I pulled in for gas and suddenly it comes back.

Have you pulled the code to confirm the P0770 is back and the CEL isn't for another code? You can throw a P0440 if you don't tighten your gas cap properly.

Good question, I do not have an ODB scanner on me as of right now. I am going to drop by Auto-Zone tomorrow and have them pull it for me.

I pulled a P0773 just now and it appears to have come back. My mechanic replaced the shift solenoid that was broken but after some reading it can be anything in the transmission causing that code. I just find it strange that it came back after filling up my tank.

Any suggestions other than taking it to the shop? I’m going to drop it off with another mechanic this weekend.

This isn't super constructive, but if you don't want to spend $120 on a dedicated gauge (UltraGauge or Scangauge) that can read and clear codes as well as provide a plethora of real-time data, at least get yourself a cheap ($35) Ancel OBD II reader or a bluetooth/app setup for your phone. You can have multiple CEL and Pending Codes that can paint a better picture and you don't want to rely on a cashier at a parts store (or even a mechanic) to advise you. Knowledge is Power!

Edit - I also have an intermittent 770 that I'm not real worried about.

I just ordered an Ancel ODB II just now. I can clear the code once I get it tomorrow and see if it comes back. I might as well do the solenoids myself since it is pretty easy to access/drop the pan.

are you over filling?

In addition to having to retrain myself to spell GAUGE and not guage I noticed I also have the Wu-Tang 'ODB' problem to overcome as well.