I had similar issues with my 2004 GMC Yukon XL. Replacement transfer cases can be purchased with or without a new encoder motor. I agree with all of the above: carefully check all of the wiring and connections first and then I would lean toward the encoder ring. Ironically I could not get a dtc to come up when my encoder ring failed.
Service 4WD
- Thread starter Sandaman
- Start date
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Mine didn't set a DTC either, but I could tell by looking at the live data (with a Tech 2) that the 'commanded' mode didn't match the 'actual' mode.
I would command mine to 4HI but it would actually be in AUTO.
rockola1971
Full Access Member
The "I would command mine to 4HI but it would actually be in AUTO" is the tattle tale. If you hear the motor move when commanding to 4hi and it is actually in Auto then you wont see the change in the tech II or any other scanner because the feedback (position) signal comes ultimately from the position sensor(Commutator) in the encoder motor. That tells you the commutator is bad (dirty usually). The key is hearing the encoder motor moving when commanded to a position. That rules out a bad encoder motor, its working because its moving.
mountie
Supporting Member
My thought might be WAY to simple....... I had a CEL light, and my DTC said, " Service 4 WD "....
I eventually found my battery ground connection was not tight. I tightened the ground and the DTC warning went away. ( and never came back)
I eventually found my battery ground connection was not tight. I tightened the ground and the DTC warning went away. ( and never came back)
Found the error. Its C0327. I don't know what to do. Encoder issue? So if I change the encoder i should reprogram it? Or is it wiring issue?
Attachments
Highly likely it's the encoder motor or, less likely, the wiring harness, but check the below video first. Encoder motors don't need to be programmed -- they are PnP. But be sure to get one with the proper spline type; yours should look like this one. The older ones have two flats instead of the star shape.
If you're so inclined, instead of replacing the encoder motor you can replace the Range Position Sensor inside of it:
While you have the wiring harness disconnected from the encoder motor, carefully inspect it for damage (if it's not clipped up on the body it can get rubbed or caught on the propshaft and damaged) and the pins for cleanliness and pin fitment.
If you're so inclined, instead of replacing the encoder motor you can replace the Range Position Sensor inside of it:
While you have the wiring harness disconnected from the encoder motor, carefully inspect it for damage (if it's not clipped up on the body it can get rubbed or caught on the propshaft and damaged) and the pins for cleanliness and pin fitment.
strutaeng
Full Access Member
Try the encoder motor range sensor. That's what was bad on my transfer case. When I took mine apart and checking resistance with a DVOM, the reading was all over the place when turning the little wheel by hand. The new one had like a smooth, linear reading. There's 3 little electrical connectors on the ring.
Post #11:
Post #11:
"Service 4wd" message - PerformanceTrucks.net Forums
Tuning, Diagnostics, Electronics, and Wiring - "Service 4wd" message - Hey guys, I need some help on this issue. This is a 04 Suburban 2500 4x4 with the LQ4/NP 246. I bought it from the guy and it was his Dad's and he said this message popped up but it worked just fine in 2wd, which is the case...
www.performancetrucks.net
InterceptorF
Member
Its been in the single digits here in Colorado Springs (cold). My 2003 Tahoe was slipping up the drive in the snow (2wd) so I attempted to put in from 2WD to 4WD and the "Service 4WD" came on. I replaced the encoder motor about two years ago but I also noticed that the LED's on the switch were not lit or telling me what setting I was in. I am thinking its the encoder motor again but I am going to check the connector after reading Sandaman's post. I'll let y'all know.
InterceptorF
Member
I took the encoder motor out and disassembled it to parade rest ( all the way - the gearhead, the encoder) cleaned it out , cleansed the plastic disc with carb cleaner ( trans fluid was in it) put it back together and it seems to be working fine now so I don't think its my encoder motor. I can make it turn with a battery connected to the big black and big red wires - clockwise / counter-clockwise depend on which way I attach the battery. I aligned the spline key to what I saw from the shaft ( about 6:30 ish) and put it back in and the Tahoe was in some sort of intermediate place - like a neutral with bad sounds. I took the encoder mtor back out, moved the spline with vise grips, again aligned the spline key using the battery to move the motor and stuck it back in. Now it seems to be in 4 low (ABOUT 7:00) Does anyone know where the spline key should be for 2WD?
Typically they are shipped, removed, and reinstalled with the TC in neutral. If you look at a few stock pics (like the one I posted above) most should show that position.
Now, I don't recall on mine but I thought the middle position on the TC shaft was neutral. I could be wrong. Maybe @rockola1971 would know?
Here's a possible solution, but it would require opening up the encoder motor again.
Now, I don't recall on mine but I thought the middle position on the TC shaft was neutral. I could be wrong. Maybe @rockola1971 would know?
Here's a possible solution, but it would require opening up the encoder motor again.
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