07 Yukon C0306 Service 4wd (most fixes tried already)

[Tray0625]

C0306 (Motor A/B Circuit) persists for over a year and all the parts and $ thrown at it. Please Help!

I have done;
- actuator
- selector switch
- TCCM
- TCCM wire harness
- Encoder Motor & relearn flash
- Checked all external grounds, cleaned
- checked all fuses
- I do not see broken wires anywhere

I have had it at the dealership twice since I got to a dead end on what to do next. They cleaned grounds, and have not found it either. I can't keep paying through the nose for them to look either.

****clue*** Both times from dealer, once they cleared the codes with their GM scanner, the 4WD light goes off for a couple of days. In that couple of days, the 4WD WILL work correctly!! It shifts into 4hi, 4lo, N, & 2wd and functions correctly. Then C0306 comes back on.

When I clear the code with my BlueDriver, it does not work.

My next tries (if I don't set this thing on fire and walk away);

- try a different encoder motor (maybe I got a defective one?)
- clean terminals on all harnesses (pretty much already been done)
- try to find wire harness diagram and check every inch of it (please send if you have one)
- maybe replace encoder motor wire harness?


At this point I am almost considering bypassing the OEM wire harness and rewiring the entire system myself.

What would your next move be? What do you suggest?
First time posting, but have followed the forum trying to fix this. Much appreciated.

 

[j91z28d1]

I don't have any ideas about the issue, but I think you're a prime case to buy a clone tech 2. and then go from there.

 

[Geotrash]

C0306 (Motor A/B Circuit) persists for over a year and all the parts and $ thrown at it. Please Help!

I have done;
- actuator
- selector switch
- TCCM
- TCCM wire harness
- Encoder Motor & relearn flash
- Checked all external grounds, cleaned
- checked all fuses
- I do not see broken wires anywhere

I have had it at the dealership twice since I got to a dead end on what to do next. They cleaned grounds, and have not found it either. I can't keep paying through the nose for them to look either.

****clue*** Both times from dealer, once they cleared the codes with their GM scanner, the 4WD light goes off for a couple of days. In that couple of days, the 4WD WILL work correctly!! It shifts into 4hi, 4lo, N, & 2wd and functions correctly. Then C0306 comes back on.

When I clear the code with my BlueDriver, it does not work.

My next tries (if I don't set this thing on fire and walk away);

- try a different encoder motor (maybe I got a defective one?)
- clean terminals on all harnesses (pretty much already been done)
- try to find wire harness diagram and check every inch of it (please send if you have one)
- maybe replace encoder motor wire harness?


At this point I am almost considering bypassing the OEM wire harness and rewiring the entire system myself.

What would your next move me? What do you suggest?
First time posting, but have followed the forum trying to fix this. Much appreciated.

I have had a couple of situations on these trucks where disconnecting wiring to replace a part resulted in intermittent error messages over the following weeks after the repair. In both cases, taking apart the connectors and hitting them with electronics or electrical contact cleaner before putting them back together again, solved the issue. The first time was on the autoride shock connectors on my '07 a few years ago. The second time it was the left front wheel speed sensor that I replaced a few weeks ago on my '07. Kept getting an ABS lights and chime every time I drove it until I cleaned the wiring connector on Monday. No more problems since. Might be worth a "shot".

 

[j91z28d1]

if you really wanna deep dive into what the dealership tech probably doesn't feel like doing. this is the tree I found. I guessed it's not the all time awd t case since you said you have a 2wd option

 

[Tray0625]

I have had a couple of situations on these trucks where disconnecting wiring to replace a part resulted in intermittent error messages over the following weeks after the repair. In both cases, taking apart the connectors and hitting them with electronics or electrical contact cleaner before putting them back together again, solved the issue. The first time was on the autoride shock connectors on my '07 a few years ago. The second time it was the left front wheel speed sensor that I replaced a few weeks ago on my '07. Kept getting an ABS lights and chime every time I drove it until I cleaned the wiring connector on Monday. No more problems since. Might be worth a "shot".

I'll give that a shot, thanks!

 

[Tray0625]

if you really wanna deep dive into what the dealership tech probably doesn't feel like doing. this is the tree I found. I guessed it's not the all time awd t case since you said you have a 2wd option

Thanks, I will check it out. And yes, 4WD not AWD.

Much appreciated, all this info is from the tech 2 you referred to?

 

[j91z28d1]

that info is from a pay shop software . the tech 2 is the dealer level scanner. but instead of the $2k plus you can get them for about 300$.

 

[Tray0625]

Alright guys, I have a theory. Give me your feedback please.

Truck displays C0306-02 (Motor A-B Circuit short to ground)

Couldn't I just run my own new external ground, rather than trying to find where it is shorted?

If so, any suggestions on best spot to run a new ground?

I will be thoroughly cleaning all connectors and meter testing them over the weekend. But I am really curious if I can solve it by just running my own ground.

Let me know your thoughts, I will update on if I find anything this weekend.

Thanks!

 

[Fless]

According to the code, the circuit is already shorted to ground. Running another ground wouldn't cure that.

 

[Tray0625]

Guess it's time to get the test light out. Anyone have wiring diagrams for this system?