05 Silverado electrical issues..?

wardy75 · February 18, 2014

Hello all, found this forum doing a Google search so I joined up to see if I could get some guidance.

I've got a 2005 Silverado LS 4x4 with the 5.3 Vortec its got 55k miles...back in October it threw a code for knock sensors and input off changing them out, well then the cooling fans started coming on by themselves with no key in ignition and killed my battery.

I replaced it and the CE light stayed off for a while. Then the fans started up again and shortly after it threw the knock sensor code again. I carried it to the dealership and the tech found water in the blue connector on the PCM. He cleaned it out and cleaned the plug and applied dielectric grease. Made it 2 weeks and it threw the knock sensor code again and then one day it wouldn't start...it would turn over but wouldn't fire off. Almost like it wasn't getting fuel.. Had it towed to dealer and they said may need a connector on PCM or a new PCM. They called back and said it was the PCM so they replaced it. 1 day later, check engine light comes back on and I carry it back and they say the knock sensors need replacing. So I hold off for a week to pool up some cash which brings me here now....Now, it wouldn't start but after I tried it a couple times it did start but I have no oil psi, amp indication, fuel level indication and the ABS light is on..My neighbor has a scanner and we tried to get a code but it wouldn't connect and the fuses are good that carry the on board connector port. I called the dealer and asked what the cost of a new blue plug and harness would run because I suspect the harness is bad somewhere....I understand the same harness carries the fuel injection, knock sensors and some other things....

Am I assuming right or do I have a deeper electrical issue? Please help!! Lol

Via Droid Maxx using Tapatalk

Edited February 18, 2014 by wardy75

Doug_Scott · February 18, 2014

Start with the basics, you have already ckecked fuses, did you also check battery connection and condition? You also need to check negative battery cable connections at both ends, on all wires. Make sure you have good connections between battery negative connection to body, frame and engine. There must be connections between the three components. Do not assume that there is a connection because they are bolted together. They have bolts connecting, but, they also have rubber isolating. So make sure they are wire connected.

It really sounds like you have a bad connection. If you want to check them, you will need to unplug the connectors, look for corrosion, and look inside the connector where the wires attach to the terminals for any corrosion. Usually white or green (depending on terminal metal) powder or paste. Gently pull on each wire, looking for breaks in insulation, and also look for the unsulation "stretching" when you pull the wire. If you can see the insulation look ed it is stretching, the wire is likely broken inside the insulation, and only the insulation is holding the wire together, broken, but looking connected.

Remember that most wires used for the EFI system carry 5 volts. Does not take much corrostion to create big issues. Voltage is essentially the "pressure" behind the current..

Have you been doing engine shampoos at the local car wash? The weatherpack connectors will keep average water exposure out of connections, but, the high pressure wand type of self service car washes can overpower the weatherpack connectors.

Doug_Scott · February 18, 2014

I often fix my car by myself. In my opinion, may be you should make a diagnostic and you can do it in a garage or you can do it by yourself if you want to do it by yourself you need some tools.

He has already tried to access data from the diagnostic port (ALDL) and said it is not working.

wardy75 · February 18, 2014

Thanks Doug_Scott for the reply. The battery is new I haven't dug deep into checking all connections yet. And honestly I'm afraid of delving too far into electrical issues. Lol..I've not washed the engine compartment but suspect it came from going through several mud puddles at my hunting club. Nothing anymore than 6"-12" deep and I wasn't rooting around. But after that was when the problems started...

I'd like to think I could fix it myself but I definitely don't have all the necessary tools I'm sure...I might could get a hold of the ones I really need.

Where are the main ground straps for my truck? Anyone know or think Google will tell me?

Via Droid Maxx using Tapatalk

gmtech4 · February 18, 2014

i didnt read if ya replaced the harness for the 2 knock sensors ,,,,,,it is a common issue along with the knock sensors taking a crap ,,,,,,,if that is done ,,,you have not mentioned 1 code number here ,,,the dealer diagnosed the PCM and IS ON THEM to fix it right not you ,,,

this truck needs to be hooked up again from scratch with codes cleared and drivin ,,,,not by you either

my 2 cents

you have to let us know what happens ,,,keep us informed (alot of guys dont do that and we are reminding everyone to keep us in the loop ) ty

wardy75 · February 18, 2014

I'll keep this thread alive with my findings from the dealer "govtech4" I agree its on them...I feel like they've been trying to shoot me straight but am not sure if PCM was an issue from start...its been at the dealer several times and I've not been charged for diagnostics on it so I don't feel they're trying to just get money...they're gonna replace the knock sensors and I made sure they'll get the harness as well...I'll keep everyone informed and thanks for the help too!!

Via Droid Maxx using Tapatalk

gmtech4 · February 18, 2014

thx steve !!

wardy75 · February 18, 2014

No problem!

Via Droid Maxx using Tapatalk

Doug_Scott · February 18, 2014

Ground connections tend to done the easy way by factory. Follow the negative battery cable away from battery and see where it ends. You may also find the negative cable has more than one wire running off of it. Follow them as well. Since this started after a deep water run you will want to look at any connections that could have been in the water. Look for any modules that would have been in the water/

If you have issues with sensors already, then get that fixed first. Follow what govtech4 has suggested. Quite possible it is the same issue.

wardy75 · February 18, 2014

Thanks....I just left the dealership and the same mechanic that has been with it since this started is the only one working on it. Water was found in the blue plug again. I have not been anywhere, just normal driving back and forth to work. Even before, it wasn't deep water/mud...just mud puddles. Either way, he's gonna clean connector up again, dry it off, apply fresh dielectric grease and replace the gaskets for the PCM blue plug. I have no idea where the water is coming from and neither does he...I'll keep everyone informed too..

Via Droid Maxx using Tapatalk

Doug_Scott · February 18, 2014

Did it rain? Where is the plug that is getting water in it? Car wash? Anywhere near the vent for the a/c drain?

wardy75 · February 18, 2014

It has rained and snowed a little too...I haven't been to the car wash any. The plug getting the water in it is the blue connector at the PCM. There's 2 long plugs one is blue and one green. Drivers side fender well just below battery. It makes no sense! Lol

Via Droid Maxx using Tapatalk

wardy75 · February 21, 2014

Quick update,...had a new PCM connector installed. So far so good. Hopefully this will eliminate the problem...still have no idea where the water intrusion at the Blue PCM connector is coming from.....hope this works.

Via Droid Maxx using Tapatalk

wardy75 · February 27, 2014

New update.....for off work this eve, got out of truck and locked doors....cooling fans still running. Sounds like I'm back at the beginning again....no check engine light yet but I expect one soon...any ideas? Haven't checked the temp sending unit but the relays are fine.....I'm about to give up. Going to look a new truck next week...lol

Via Droid Maxx using Tapatalk