How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Reggie Whiddon Your Own Question
Reggie Whiddon
Reggie Whiddon,
Category: Chevy
Satisfied Customers: 162
Experience:  Lead tech at river regions auto
Type Your Chevy Question Here...
Reggie Whiddon is online now
A new question is answered every 9 seconds

I have been fighting a 4x4 issue with our 2007 Yukon SLT. No

Customer Question

Customer: I have been fighting a 4x4 issue with our 2007 Yukon SLT. No dash warning message has ever been present. All initial signs pointed to a bad encoder motor so I initially replaced that with all I could find on a Saturday... a Dorman unit. It appeared to be DOA so I took that back and purchased an AC Delco reman unit. The original encoder motor was in 2wd when removed. I manually rotated the shift linkage to Nuetral and installed the new AC Delco encoder motor. Unfortunately that didn't fix anything as now the vehicle was stuck in Neutral. Rotating the selector knob to any position did nothing. When a scan tool was connected the new encoder motor displays NEUTRAL... as does the dash selector knob. However when the dash knob is rotated to any other position the encoder motor itself does not change position. We get a series of blinks and then no change occurs. The front axle actuator engages and the scan tool shows when 2wd / Auto / 4x4 / 4Low is requested but no change at the encoder motor itself ever occurs. I pulled the new encoder motor down (and left it plugged in) and watched it for any signs of movement when different positions were selected and there is none. All I can hear is a quick click from the "LOCK" request. I can quite easily manually select different transfer case ranges with pliers. I had a local shop flash the second to newest GM software via their TECH 2 to the TCCM and while the update was successful it had no effect on being able to select any range. The vehicle remains stuck in Neutral. In order to drive the vehicle I removed the new encoder motor and select 2wd by rotating the transfer case selector manually. I reinstalled the old encoder to keep the transfercase contaminant free while we drive it. The old encoder motor will not change ranges either. I can attempt to select AUTO and it flashes like it's trying but then reverts back to the original 2wd range. When trying to select 4-HI or 4-LOW there is no blinking at all. I'm starting to wonder if the TCCM itself is bad. I can't find any for sale locally (used or new) and would hate to spend $250.00+ on a new one as I can't return it should the TCCM not be the cause of the problem. Suggestions on any other steps that possibly pinpoint the issue would be fantastic. We've got snow/ice on the roads and 2wd isn't cutting it. Thanks!
JA: Thanks. Can you give me any more details about your issue?
Customer: All details are stated above.
JA: OK got it. Last thing — JustAnswer charges a fee (generally around $18) to post your type of question to Chevy Experts (you only pay if satisfied). There are a couple customers ahead of you. Are you willing to wait a bit?
Customer: Yes.
JA: OK. Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.
Category: Chevy
Expert:  Reggie Whiddon replied 1 year ago.

Hi thanks for the question. That is a goor one and I agree with you about the tccm. Let me review the manual aND find the process so we can make sure

Expert:  Reggie Whiddon replied 1 year ago.

Okay I have reviewed service information, bulletins and pattern failure records. You say you had it relaxed to updated software did they perform the clutch reset and relearn? Also try unplugging and plugging th e tcm. At last ck the powers aND grounds to tccm they are a pink wire in gray connector red black wire in black connector and the ground is a black wire in black connector. If all of this checks and resets were done replace the tccm

Customer: replied 1 year ago.
The TCCM was removed from the vehicle for a number of days and when reinstalled there was no change in operation. The Clutch Reset was performed with a TECH 2. No change in operation. Without knowing the expected voltage on each wire I can do nothing but check continuity. I would expect the voltage on one of the 7 wires leading to the encoder motor to either increase, decrease or switch polarity but I don't know exactly what I should be testing for.
Expert:  Reggie Whiddon replied 1 year ago.

Have you checked the power and grounds I told you about?

Expert:  Reggie Whiddon replied 1 year ago.

4.5 volts each on pin D and E

Expert:  Reggie Whiddon replied 1 year ago.

Expert:  Reggie Whiddon replied 1 year ago.

That's all the wiring and circuits let me know you got that and if you need any help testing it.

Customer: replied 1 year ago.
I can't view the link. I tried it from a desktop and a laptop and neither works. It appears to require a paid subscription.
Customer: replied 1 year ago.
Should the pink wire in gray connector be 12v? Should the red/black wire in the black connector be 12v? I will check the black wire in the black connector for ground.I can check for 4.5v on the pins as soon as I can figure out which is which.
Customer: replied 1 year ago.
I've attached a picture of the plug side of the TCCM. The plug colors of what I actually have don't match what you are saying I should be looking for.
Expert:  Reggie Whiddon replied 1 year ago.

Sir thank you so much

Expert:  Reggie Whiddon replied 1 year ago.

Sorry I hAve been havng computer problems last couple days. Thst last message I sent to someone else. And the link didn't come out right.I am going to try something diff so hold on

Expert:  Reggie Whiddon replied 1 year ago.

Sir my deepest apologies. I have had computer and Internet issues price you pay for living rural. I am good to go now. Have you resolved this issue? If not please alow me to help you resolve this. I appreciate your question and feel terrible for my delays. I will be available by phone or message

Thank you


Customer: replied 1 year ago.
Not a problem! I was able to verify the TCCM is receiving (14v) when the engine is running. The primary ground seems good. I don't know which pins I should see 4.5v at though. I am curious to know what voltage readings I should find at the 7 wire connector at the encoder motor.
Expert:  Reggie Whiddon replied 1 year ago.

I believe it was 2.5 but let me make sure on that. And thank you for your understanding people like you are a blessing to have. IL be rigjt back

Expert:  Reggie Whiddon replied 1 year ago.

Disconnect the plug to the encoder/motor assembly at the transfer case.

2. With the key on, check the Light Green/Black wire for a 5-volt reference. Check the Black/White wire for ground.

3. Plug the encoder/motor back in, then probe the Brown/White wire with a meter.

4. Feedback voltage on the Brown/White should be as follows:
2 Hi = 2.7 volts
Auto = 3.4 volts
4 Hi = 3.9 volts
4 Lo = 0.7 volts

5. If voltage is incorrect, check the wiring back to the Transfer Case Control Module (TCCM) for problems.

6. If OK, then replace the encoder/motor assembly.
Mark Owens

Expert:  Reggie Whiddon replied 1 year ago.

Best I could find