P2635 Code

IASilverado · April 4, 2019

Hi guys I'm new to the site.

I have been doing some searching to try and diagnose my problem. I have a 2017 Silverado 1500 and I keep getting a 2635 code. It's out of warranty so I am trying to figure it out without taking it to the dealer. It was at the dealer a few weeks ago for this problem and they replaced the fuel tank pressure sensor and the EVAP purge valve. I also ordered a fuel line pressure sensor and will be replacing that in a few days. I can clear the code and it will come back a few days later. I also noticed to day that my volts gauge dropped to around 12v when I was driving and the cel came on shortly after. Somehow my voltage drop is affecting my fuel pump performance. The voltage drop is completely random from rpm/speed/or what electronics are on. Sometimes it will be just over 14 and other times it drops to around 12. It doesn't jump around and it usually stays at that reading for a while. Anybody have any ideas? Alternator? short circuit? Thanks

silveradosid · April 5, 2019

check ground connection 121 it is for the fuel sensor and the fuel pump control module

IASilverado · April 5, 2019

Ok thanks I will look into that.

Are the schematics posted on this site anywhere? Looking for the location of that ground. I'm assuming it is close to the tank/spare tire and grounded to the frame.

IASilverado · April 8, 2019

Well that didn't fix the problem. I replaced the fuel line pressure sensor and also cleaned the ground located under the drivers door. I also checked the two grounds located in the front corners of the dash and they looked fine. For some reason when my alternator switches to the lower amp setting around 12.6V and I give it moderate acceleration I get a cel with p2635 code. Anyone have any other ideas?

Russell Bond · October 1, 2019

what did you find?

cadillacvelocity · October 29, 2019

I am also curious what you figured out, I just bought a 2017 and mine is doing the same thing with the battery voltage and throwing the same code. The fuel pump at the tank also has that scream that the late '90's Chevy's had before they went out.

Maximum velocity · March 31, 2020

On 4/8/2019 at 12:55 PM, IASilverado said:

Well that didn't fix the problem. I replaced the fuel line pressure sensor and also cleaned the ground located under the drivers door. I also checked the two grounds located in the front corners of the dash and they looked fine. For some reason when my alternator switches to the lower amp setting around 12.6V and I give it moderate acceleration I get a cel with p2635 code. Anyone have any other ideas?

I am also curious if you ever found a solution.

MaverickB · June 4, 2020

I am having this identical issue with a 2017 GMC 2500 with the 6.0...everything you said I am having the same issue with...Does anyone think changing the battery could be a fix?

Edited June 4, 2020 by MaverickB

warren smith · July 3, 2020

Any update on this post?

warren smith · July 3, 2020

Is there any update on this post ?

Redwater08 · August 15, 2020

Hi all, I'm having the same issue with the code P2635 on my 2017 GMC 1500 4wd in including the voltage drop. Has any body find the solution to the problem?

Jamie Richards · August 16, 2020

Hey guys having the same issue with my 2018 suburban LT and fuel gauge will not read even with a full tank if gasoline

Ibdmann5 · April 23, 2021

On 3/31/2020 at 11:59 AM, Maximum velocity said:

I am also curious if you ever found a solution.

SAME 2017 Siverado. Replaced battery awhile back. Now P2635. The more I look into it the more I hate Chey. Some people are saying it's a problem with the programming of the computer

Ibdmann5 · April 23, 2021

Sprayed computer above spare tire with carb cleaner haven't had the code come back been a couple days. I did replace battery at 30,000miles. 2017 silverado. Fingers crossed