Problems when it's really wet

[Toomanyhobbies]

Yesterday we had a ton of rain here in the Philly area and I drove through a few moderately flooded roads. The truck then thought it was in 4L (I could hear that the hubs locked but I obviously wasn't in 4L) and the engine hesitates and the trans tries to to into 4th shortly after accelerating from a stop. This situation dissipates as I accelerate, but I don't have full power.

I have noticed this before when it's really wet out. Truck is a 2004 5.3 LS with 190K on it. The "service 4WD" light has been coming on intermittently for a couple years now but no CEL or any other indication.

Any thoughts?

Thanks

 

[Chubbs]

I had to unplug the main transfer case connector underneath the truck and let it dry out over night. Just look for the biggest socket above the transfer case, unplug the connector and see if any water is in there. It kind of hangs down so I had enough slack to tuck it up higher where water couldn't saturate it everytime I drove through a puddle.

If you don't have water in the connector then start going through anything else dangling around under there. Unbolt the grounding points, clean it all up with a wire brush and reconnect.

You will just have to crawl under there and get your hands dirty.

This is the simple fix. If the 4wd lamp has been going on & off without the presence of water then you have bigger problems than a compromised circuit. All bets are off diagnosing 4WD without the proper equipment. You had really better know your way around a multimeter and become 1 with the test light if you don't have a Tech2 or know a seasoned GM tech that doesn't mind stopping by to help you out. The encoder ring is the 1st part I would set my sights on. if you decide to throw parts at it, a search on YouTube will produce tutorials for replacing any of the electronic 4wd parts (4) that can & will fail. These parts range in price from $40 to $240 so you don't want to guess wrong more than twice.

I suggest you deal with it soon because you are going to look over 1 day and find that you have just done 20 highway miles in 4-HI when the TC motor starts randomly changing modes without your knowledge.

 

[Toomanyhobbies]

Thank you.

So as an update, later in the day yesterday it was sunny and when things dried out it was fine. Service 4wd light on again. I am fairly certain encoder motor is bad from research I have done.

Today it was fine, and then this evening same situation. But here is the thing, which is does this it also doesn't shift right (hesitates and goes straight to 4th from stop) and hubs engage but I am not in 4wd. I also now have CEL (first time this has happened) as a result of this episode.

I think it a short (connector as you said) or ground. Will look at those tomorrow. I have mech who is great and will get encoder motor price from him. I am not sure I am up for that job.