4 Wheel Drive Inoperable?

Hello, I can help you with this, the first thing I would do is check the trans IGN and 4wd trec fuse in the fuse panel under the hood. If this is okay, disconnect the transfer case and front differential actuators then scan the truck again to see if the TCCM come back on line. If so plug them back in one at a time to see which ones takes the TCCM offline, this will be the bad part. Please let me know what happens so we can go from there. Ken

I ran into something really similar on a GM truck before bunch of codes + 4WD just stopped working.

Turned out after chasing it for a while, it wasn’t the transfer case or the shift motor at all. It was actually a power issue to the TCCM.

With what you’re seeing Lost Communication with TCCM and it popping up KOEO my first thought is the module might not even be coming online at all.

If it were me, I’d start simple before throwing parts at it:

make sure the module actually has constant power + ignition power
double check the related fuses

Stuff can look fine on the surface but if power is unstable, the module just kinda “disappears” and you get exactly this kind of behavior.

Once you’re 100% sure power/ground is solid, then maybe start thinking about the module itself.

I could be off, but that’s where I’d start I almost went down the transfer case rabbit hole on mine before realizing it was just a power issue lol.

This time you are speaking my thoughts exactly. I repaired and/or replaced every ground on the truck and installed 4 gauge Positive and Negative Battery Cables, as well as the charge wire from Alternator. Cleaned the connectors/connections on all the 4 WD, Trans, Stabilitrak, and Transfer Case related components I could find. The fact that the lights and codes popping back up immediately when I turn the key on, has had me on power/ground hunt for a week. My schedule doesn't afford me a lot of time to diagnose it but every 10 or 15 minute break I get is spent with a scanner, a DVOM, and a test light in my hands and a tube of dielectric grease in my pocket. I have not taken the dvom to the TCCM yet because I haven't located a Pin out chart for it, but I am looking.

Nice addition to the thread BENNETTLYLEEEEE, here are the wiring diagrams so you can continue the testing. Check out the images (below). Please let us know what happens.

I've been working crazy hours and just now had a opportunity to do some circuit checks on this thing. I attempted to pull up the diagrams you sent me so I could identify Voltage and Ground Pins at the module, but for whatever reason, the diagrams will not load when I click on them. Originally, I saw your reply, I opened it to read it, and the media loaded automatically. Now they won't load at all. I found them by logging in to my dashboard and selecting "my questions." They are there, listed as media links but they refuse to open. Can you send them again please?

Circuit 19 at TCCM listed as Constant Battery Voltage, Failed. Grounds and Circuit 12 (Voltage key in run and key in crank) all passed. Circuit 19 is Grey/Red wire through firewall and into underwood fuse & relay center. It is fed through 30 amp fuse #6. Fuse #6 passes. Voltage across fuse but not present on circuit at TCCM. I PULLED the fuse & relay center to check for break between it and TCCM. Wire, beginning to end is complete and intact. Closer I inspection revealed a one inch segment of the wire, where if you peeled back the layer of insulation, it revealed that out of 19 strands of copper only 1 strand remained unbroken and undamaged. The other 18 strands within that segment of wire were all broken and unable to carry Voltage. I replaced the wire from the fuse and relay center all the way to the bulkhead. There is now a known good circuit on #19 at the TCCM, and although I assumed it would correct the issue, it only changed the symptoms. The Stabilitrak light no longer illuminates when KOEO, and the Traction Control malfunction is no longer indicated. However the Service 4WD message still comes on immediately when key is turned to on, the 4WD select indicator stays illuminated at "4 Auto" no matter where you put the selector, the 4WD is not engaging, and now there are different fault codes the trigger immediately after clearing them. They are:

Woops, I got a little trigger happy and sent that before giving you the codes LOL. Here's what they are now:C0306-02 Range Actuator Cintrol Curcuit-short to ground.
C0364-04 Front Axle Engagement Actuator Control Circuit-open
and C0379-08 Front Axle Engagement System-Performance-Signal Invalid.
So what are your thoughts? I just very nearly cured it today by jacking up the radiator cap and replacing everything below that

Still with me? Or did I lose you somewhere under the relay center? LOL

Hello?? Are you still getting my messages?

Sorry for the delay, it sounds like the front differential actuator is shorted or the wiring harness is rubbed through somewhere, can you inspect the harness, also is this truck lifted? If so the wiring can get stretched causing the issue. Please upload an image or short video of the front differential actuator and wiring so I can see it please.

Vehicle details: 4WD / AWD

Hi guys! It's me again. Kevin (Rarebladz) with the multiple lights on and no 4 wheel drive. I posted my original question and you replied. I replied to you and you back to me. Below is a copy ofnthe most recent message I sent that I don't think you got. I have sent about 4 with no response so I had to assume something is wrong with the thread. That's why I thought I would use the ask question option again to see if I hear back. You know the rest of the story, except this latest discovery and symptoms are changing. Please let me know your thoughts

Circuit 19 at TCCM listed as Constant Battery Voltage, Failed. Grounds and Circuit 12 (Voltage key in run and key in crank) all passed. Circuit 19 is Grey/Red wire through firewall and into underwood fuse & relay center. It is fed through 30 amp fuse #6. Fuse #6 passes. Voltage across fuse but not present on circuit at TCCM. I PULLED the fuse & relay center to check for break between it and TCCM. Wire, beginning to end is complete and intact. Closer I inspection revealed a one inch segment of the wire, where if you peeled back the layer of insulation,

Sorry for the confusion, the site got updated but it seems to be working now. So to confirm he fuses and power lead are good, the grounds are good and you replaced the actuators and control switch, it sounds like the TCCM is bad but lets do a CAN scan to see if any codes are stored, this video will help, you may have a broken transfer case as well, does this truck have oversized tries and do you like to go offroad with it?

CAN SCAN - https://youtu.be/u-4syLc-ifQ

Please go over this guide and get back to us.

Hi Ken. No Sir, I have not replaced the actuators and control switch. I have replaced all the grounds on the vehicle, upgraded charge line from the alternator to 4 gauge with pure ofc terminals and replaced both battery cables (with 4 gauge) and all battery cable terminals/connectors. I also disconnected, cleaned and reconnected all connectors related to the 4 wheel drive system. None of these procedures had any effect on the issue. Then, I found a fault in circuit 19, "constant" power feed to TCCM. I replaced that circuit and the Stabilitrak light and Traction Control light went away. It also got my cruise control back. BUT THE 4 WHEEL DRIVE STILL DOES NOT ENGAGE AND THE "SERVICE 4WD" LIGHT COMES ON THE INSTANT I TURN THE KEY ON AND STAYS ON. THE STATUS INDICATOR IS STUCK ON 4WD AUTO AND THE CURRENT CODES ARE THE FOLLOWING: C0306-02 Range Actuator Control Circuit-Shorted To Ground, C0364-04 Front Axle Engagement Actuator Control Circui-Open, C0379-08 Signal Invalid. So what is the most common known fix for identical models with the same symptoms and displaying the same 3 codes? Or is there a diagnostic flow chart for one with these 3 codes? Or what would you suggest as a next step?
In addition, I did the system scan and it only revealed these codes and 3 or 4 codes pertaining to the radio or infotainment system. Oh yeah! I forgot about your last question so I had to come back and add this: "No" the truck has not been lifted and has original 20 inch wheels. I had intentions of lifting it and installing trail tires but there's no sense in that if the 4 wheel drive isn't going to work LOL

Yep good call, so since you had the system apart the codes maybe residual, I would clear the codes and then drive it for a short time and run the codes again. It sounds like the transfer case shift actuator or the front differential actuator may be bad. Let me know how it goes.

No Sir. I ran a full scan with KOEO. Found 2 TCCM faults, 3 Radio system faults and 2 BCM faults. I "erased all codes", got the success message, and without turning the key either direction or making any changes, ran the scan again. Before the scan could complete the Service 4WD light was back on. The rescan revealed these fault codes: (1) EBCM Code U0403-71 Invalid Data Received From Transfer Case Control Module. (1 of 2) TCCM Code C0306-02 Range Actuator Control Circuit Short to Ground. (2 of 2) C0364-04 Front Axle Engagement Actuator Control Circuit Open.
The Service 4WD Light remains on, the 4 wheel drive does not engage and the position indicator is stuck on "4 wheel drive auto."

Yep we got some work to do,

TCCM C0306-02 — Range Actuator Control Circuit Short to Ground
This points to the transfer case range actuator/motor circuit. The module is seeing the range actuator control circuit pulled to ground when it should not be.

TCCM C0364-04 — Front Axle Engagement Actuator Control Circuit Open
This points to the front axle actuator circuit being open. That can be a bad actuator, disconnected connector, broken wire, corrosion, or a failed driver inside the TCCM.

EBCM U0403-71 — Invalid Data Received From Transfer Case Control Module
The ABS/EBCM is receiving bad or invalid 4WD status data from the TCCM. This is probably because the TCCM cannot correctly command or confirm transfer case/front axle position.

Most likely causes

I would look for these in this order:

Damaged wiring harness near the transfer case or front differential
Corroded, loose, or water-contaminated connectors
Bad transfer case range actuator/motor
Bad front axle engagement actuator
Blown fuse or poor TCCM power/ground
Failed Transfer Case Control Module, less common, but possible after circuit checks

Because you have both a short-to-ground code and an open-circuit code, I would strongly suspect a harness/connector issue before condemning modules. Let me know, we are getting closer.