05 Suburban 4WD - Continued Oddities

[kbro19067]

may need help from "the roadie" if he is still around; but will take sound advice from anyone.

Relevant details: 4 button selector switch (an NP8, with Auto4, 2wd, 4hi, 4 low buttons).

Relevant Parts: have 2 selector switches, have two encoder motor units, have two tccm's as of today.

 

Basic issue: the transfer case encoder motor will not change positions. Symptom: press a button other than the illuminated one for the current position of the encoder motor --> BLINKING of selected position, but eventually blinking stops and current position stays lit throughout and after. Motor doesn't activate.

 

More details: With key off, I'll swap the transfer case motor unit that is connected to the harness clip (note: NEITHER is on the transfer case at this point).

Turn key on/full start --> dash switch lights solid in the spot of the connected motor position. Select another position and the light blinks, but nothing happens.

Turn key off -- & -- switch either the dash switch or the motor unit plugged in; repeat --> same results with any combination.

Ran to local yard today and picked up a TCCM; presuming that was the issue as it was the only part left that hadn't been swapped yet.

New motor is in NEUTRAL, as shipped by after market vendor (not rebuilt as far as I know). It has never moved.

Old motor is in 4Low at this point. After pulling it off - it wouldn't change at all / usually Service 4wd would come on after key on and/or starting, sometimes light on the switch, usually switch all dark (except the lights cycle during key cycle on/start), after pulling and new motor not changing at all, reconnected it and it moved positions ONE TIME ONLY. {sidebar: at the time I thought that the new motor unit was bad and that there may be some mechanical transfer case issue that the old motor couldn't overcome; however that soon dashed in that upon cycling the key the motor would no longer move at all - even after disconnects, etc.} That made me suspect that the tccm must be the issue because the only thing left was wiring.....

 

Plugged the 'new' TCCM in with the key off, black, tan, then 4-pin connector. key on and it seemed to be like earlier. However, while running, pulling the front fuse --> service 4wd, and putting it back after 30 sec --> message goes away but no operational change. (the old TCCM, once fuse pulled and later re-inserted, the message would not go away until key cycle).

 

 

Any further ideas, or better yet - what am I missing?

I have an Actron scanner, but I do not think that it does tccm codes.

To any genius who'll suggest dealer - they couldn't read the Service 4wd codes ~2years ago; unless it was on at the time and when I eventually caught it in that state, they said the encoder motor sensor was the cause. But, due to the cost and being intermittent - in 2wd just driving or starting and without cause the service 4wd would appear, very random. Battery off seemed to fix it for a month or so, then random again; but found that auto4wd never seemed to cause it. Odd, but okay. When issues came up recently, i searched again and found a video to check the switch itself -- and the one (think awd) was not the right resistance (per the video), ordered another and it came and read the same (figured bad video info, but I now had a spare). At that point, figured the dealer saw the encoder code -- let's replace that. Went with a whole unit instead of rebuilding / just to avoid confusing myself "just in case" it didn't work after tearing that apart. That got me to today.

 

OH, saw one video (from 1a-auto) about replacing the tc motor - to check the ground spot under the drivers door. Found it easy, and seemed okay, but we cleaned it up anyway and put back together before attempting the motor swap project. Saw the ground check as a 'couldn't hurt' activity.

I have an can run a multi meter; but can't believe things are this "fragile" electrically.

 

And as the final PS - this truck was mine from new; had a 4wd issue under warranty ~06-07 that was a mechanical rebuild due to filings in the oil, and subsequently the dash switch as well. I didn't understand it at the time exactly, but it was fine after that (it seemed). And upon the Service 4wd that came up after service at the dealership (inspection, oil changes, etc.) and the eventually-found encoder-as-best-guess I asked for coverage - but they said no. Working that out led to the determination that it was very random and in AWD seemed to never appear.

 

Thanks for any help. Trying to be methodical at the problem, but some things are just confusing.

 

 

[kbro19067]

does anyone have the pin-out for the 7-pin connector at the transfer case encoder motor unit? Physically it is 8, but one is blanked. I think I have to start here to figure out which part or wire is bad.