Remote start not working GMC Sierra 2500HD 2008

[Clare Burns]

Hey all, I have a 2008 GMC Sierra 2500HD 6.0L Gasoline. Remote start is not working.

 

This sucks a lot for those of us living in Central Alberta

 

Initially the truck didn't start due to a check engine light coming from my downstream O2 sensors. My catalytic converters were cactus, so I removed them, had the O2 sensors adjusted and the engine light disappeared. That was two weeks ago. The remote start worked for one or two days and then I started having issues with it.

 

At first the remote start only worked intermittently, maybe once out of every 10 or so attempts and it was random. Then it stopped working altogether. I press the lock button on the fob and then hit the start button. The park lights on the truck flash as if it's going to engage, and then nothing happens. No sounds either coming from it to suggest it's going to start up.  I looked at a few forum posts and dealer recommendations and attempted fixes. This is what I've troubleshooted so far:

 

I start the vehicle manually, then attempt to use remote start. Nothing. I'm aware it only has two start attempts.

My lock and unlock buttons both work fine.

There are no check engine lights or lights of any kind appearing on the dash.

Hood lever sensor seems to be functioning. No hood open warning on dash. (Still may be a problem but I'd like to avoid replacing the latch and sensor unless it's my last option)

Oil pressure and coolant temperature are normal.

There is no extra key or key fob in the truck.

Hazard lights are not on.

Vehicle is definitely in park.

I replaced the battery in the remote. No dice. I do have a now remote on order just in case although it does seem to be communicating fine with the vehicle.

 

I finally found a blog that suggested that it might be the brake light switch. Apparently this can cause both the cruise control and the remote start to fail if it starts to loose it's marbles. I decided to test out my cruise control and unbeknownst to be me the cruise control will not engage either. So this morning I replaced the brake light switch (which was no easy task). I jumped in my truck to test drive it and it seemed to brake fine and the lights still worked when the pedal was depressed. Cruise control still would not engage (but I don't care as I live in central alberta and don't use it at the moment), but when I returned home, I shut down the vehicle, locked it, and attempted the remote start. It worked!! TWICE!! I was super excited, turned on the ignition to reset it, turned it off, jumped out of the truck and went to attempt it again. Nada. Nothing. No dice. Zippo. I've retried 5 times after turning on the ignition to reset it, and still nothing.

 

Can someone please suggest where to look next? Any ideas? Anyone had the same drama and found a fix? I don't want to take it into a shop, I know it'll cost an arm and a leg! 

 

Thanks!

[Colossus]

While the check engine lights may not be on, are there still any trouble codes stored in the computer?  Let's see what happens with the new FOB. 

Also- do you continue to hold down the start button on the FOB even after the lights flash?  if not, try that. 

You can also try disconnecting the battery cables from the battery (or batteries if you have 2) touch the positive cable to the negative cable for a few seconds to help discharge any accumulated power left in the system, then leave the cables unplugged for an hour or more, then re-connect, start it normally and drive it for a day or so normally, then try remote start and see what happens. 

 

[Doug_Scott]

You may want to check battery voltage.  On my truck a few years ago, the remote start would not work after the truck sat for 3 weeks between starts.  If I drove the truck weekly it worked.  When it didn't start with remote, it would start with key.  I finally replaced the 7 year old original battery with an optima red top.  No issues since.