engine codes

[1970greenc10]

Hi, my 03 Silverado 2wd with a 5.3 is throwing codes, U1002,P0725,P3531, and P0455 which I know is a large evap leak. Can anyone tell me what the first 3 codes are for. I tried googling them, but couldn't find anything.

Thanks, Marty

[Valarius_Starchaser]

DTC U1001-U1254 = Loss of XXX Communications to PCM

The other two I'm not finding anything if you want I can try to run the vin number in my system (GM) to ensure I have the correct engine and chassis

I would start by checking all of the ground over as well as battery positive

[1970greenc10]

The VIN # is 1GCEC14T53Z266959. I'll check the grounds. Is loss of communication a serious problem, because the truck still runs fine I just don't like the check engine light on.

Thanks, Marty

[68C15]

725 is an irrational speed signal
P3531 I'll have to look at work and see since it's manufacturer specific

[Valarius_Starchaser]

P3531 all I'm finding is powertrain code for other vehicles nothing listed for yours very odd

It sounds like the vehicle has some wiring loom being rubbed through that's causing intermittent voltage and "could" put the vehicle in limp mode but as of now it hasen't happened long enough to cause an issue

Maybe 68C15 will find more info or have ideas on it

[1970greenc10]

Update, I was driving this morning, and the check engine light turned off, so when I got home I scanned it again. Now all the codes I listed before are gone, and the only code I'm getting is multiple random misfires. The truck does not appear to be misfiring, it idles smooth as ever, and there doesn't seen to be any loss of power at speed. I still need to check the terminals and grounds and I'll check the harness for damage as well.
Thanks, Marty