08 electrical questions

[andrew.hoff.146]

Ok i own a 2008 ltz suburban, i live in northeast nebraska (elevation 1522ft). While on vacation to custer sd (elevation 5318ft), our burb went nuts!!! We left thursday morning after i double checked everything and all was good. Trip went great! Drove to custer then toured about 120 miles on friday morning with no problems. Friday afternoon i started it and everything on the dash was blinking. The dic said traction control off, park assist off, service suspension system so i shut it off and waited about a minute then started it and it ran fine. After driving about 25 miles my grandpa jumped out of the passenger seat and as soon as i let off the brake it did the same thing but ran fine. I drove about 2 blocks where i parked then returned about 1.5 hours later and it started fine and drove back to the hotel flawlessly. Sunday morning i started it and it ran great. About 120 miles into our drive home i pulled into a filling station and refueled. As i started it, it went nuts again, shut it off, waited about a minute and it started up fine. We drove another 70 miles then stopped for lunch. When i started it after lunch it went nuts again so i shut it off waited about a minute and tried it again. It started fine but the first and only time the ses light was on and stayed on. As i was driving i noticed it was shifting hard. Not like it was slipping but like their was no torque converter. I guess like it had a shift kit in it or something. So i drove the rest of the way home feathering the throttle in the hills so it wouldnt shift. Upon arriving home i shut it off one last time then started and the ses light was on and was shifting normal on my way to autozone. I had the guy at autozone put his scanner on it and he came up with as follows:

P0700 the tcm has detected an emission related fault~probable cause-check other service codes first

p2544 the tcm has received a torque reduction failure from the ecm~probable cause-check other service codes first

p0856 the ecm has detected an invalid signal from the torque request signal~probable cause-short circuit condition, faulty ebm, short in the torque signal circuit from the ecm

i listed the elevation thinking that might have something to do with it but maybe not... I dont know!? Another thing i thought of is/ the only time i have ever used my parking brake is in my grandparents driveway since it is an incline. I have read a few things about the parking brake assembly rubbing on wires but i looked and didnt see anything. Any one have an answer or a scenario for me!?

Since i have been home i unhooked the battery to clear codes. While it was unhooked it scarred both the positive and negative posts on the battery. I hooked it up a little bit ago and it started like new and no ses light!!! The ol lady left to go to her parents in it about 10 minutes ago and she should be back any minute... I will keep you guys up to date on everything!!! Please give any and all feedback!!!! Sorry about the novel post and thank you guys!!!!

 

[jagi0966]

The time mine went nuts it was battery dying. I would put an OE battery in it.

 

[ccapehartusarmyINF.(ret)]

elevation usually only affects things like fuel mixture and youd have to be alot higher then that to begin with
and with everything blinking like that going crazy id say its either a bad battery or bad PCM
if by chance you have a multi meter stick yer probes on the battery terminals after the vehic le has sat for a at least 30 min and see what the voltage is if its below like 12.4 12.3 volts its a good indicator yer batterys no good or on its way out

 

[Martins denali]

I second the battery or pcm

 

[andrew.hoff.146]

Since then it has not went crazy... A couple of times the park assist off has dinged and went off but so far so good! Thanks for the help now that I look like a dummy! Time to find some wood to knock on!!!


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