A few days ago, I received this message on the information center and the truck would not shift into 4WD. I read the how-to feature on this issue and tested the system a few minutes ago. Below is what I found:

• When I turn the ignition to on and/or start the engine, the lights on the 4WD switch all light up for a bulb test, then the light by the 2H stays illuminated.
• When I rotate the dial to either AUTO or 4H, nothing happens - the light next to the 2H position stays lit.
• I cannot hear any actuator noise under the truck.

I cleaned the ground to the frame and verified it was functioning by connecting a test light to battery positive and touching the probe to the ground wire and the test light lit up indicating the ground was functioning.

Per the how-to section, this would indicate the switch is defective, correct? Or does the light near the selected mode (either AUTO or 4H) need to illuminate, then revert back to 2H for it to be the switch. To me, it sounds like the switch is bad but it would be nice to hear from others that have had this issue. Thanks.

 

Im having the same exact issue. Have you hooked the truck up to a mechanics scanner and pulled the transmission codes?

 

Sure glad my 1998 Chevrolet K-1500 has a manual 4x4 shift lever on the floor. No issues at all with 4x2 to 4x4 engagements.

If I could, I'd put manual locking hubs on the front axle hubs. Too many electronics on modern vehicles for this old guy.

Yes, I know about the transfer-case actuator, but it's been hardened by myself. It will not let me down when I need it.

 

I had the truck scanned and code C0306 was the code that was stored. It was cleared and immediately reset. The scanner definition was Range actuator control circuit short to battery or open. The GM definition of the code is motor A/B circuit malfunction (from a Tech 2 scanner)

I haven't had time to get under the truck and inspect the wiring. I'm betting the transfer case encoder motor is shot - the part is over $400.00 so I want to make sure it is bad before I replace it.

I've heard the new units are produced in the neutral position and the transfer case shift shaft needs to be manually rotated to the neutral position. i have a shop manual on order from the library and plan to get back into the diagnosis as soon as it arrives. It is irritating that this thing puked at 67,000 miles...

 

Yes, it would be. unfortunately, many manufacturers of so many mechanical and electrical parts use parts not made in North America.

I saw a 1964 Chevrolet Impala while I was fueling up today at the Chevron station. It was restored to the point it almost looked like it came off the showroom floor. I'll bet most of it was manufactured in N.A. Of course it, like all vehicles was not perfect, and things have always gone bad in every vehicle ever made.

I bought a brand-new Jeep CJ-5 back in the '70s and the fuel level gauge went bad, and I ran out of gasoline. The dealership repaired it quite well, and I never had an issue with it again. I was just broken in at 2500 miles too. No encoder motor in that Jeep. It was all manual-shift, no issues in the Borg-Warner 205 transfer case. not the POS 1356 TC. It also had a -2-low position, which was nice, but you could bust something like a U-Joint if you applied too much power to it in that position. The 258 cubic-inch motor was not fast, but lots of torque, like a Chevy 250 engine has.

If you have to change your encoder motor make sure to use dialectical grease on any electrical plugs. Works good on spark plugs and coil wires, as well as anything electrical to keep water and dust out, as well as being a great anti-corrosive product. It is cheap and the best money you will ever spend.

 

I thought I'd post an update. Apparently, the transfer case shift encoder motors are down to go bad on these trucks. Not wanting to fire the parts cannon at the problem, I read up on the theory of operation. When the ignition is cycled on, the transfer case shift control module sends a voltage down the A/B circuit - the orange and tan wires - they are heavy gauge wires. If the module does not sense the voltage, it will set the C0306 code. I initially suspected the transfer case encoder motor was bad so I unplugged it and connected a 12V bulb across the harness terminals. I had an assistant turn the key to ON and the bulb did not illuminate which to me meant the transfer case shift control module (TCSCM) was not sending the signal down the tan and orange wires to the motor. If the bulb would have lit up on key cycling and switching the dash switch through the 2H, AUTO, 4H, and 4L positions, it would have meant the encoder motor on the transfer case was bad.

I wanted to rule out a break in the wiring so I unplugged the harness from the TCSCM, connected the orange and tan wires together, then checked for continuity at the encoder motor plug. I had about 7 ohms which meant the wiring was OK. I then connected a 14.4V battery from my drill to the harness under the dash and measured 14.4V at the plug that connects to the encoder motor.

I think this is positive proof that the transfer case shift control module is bad. Does anyone know if the new module needs to be flashed (programmed) once it is replaced?

 

I don't know but I think not. When I bought my 1998 Chevy K-1500 I was all over it with dielectric grease and also RTV sealant to waterproof the transfer case shift control module to the transfer case housing. So far no issues.

 

Update: I installed the new module and still receive the service 4WD message on the dash. In addition, there are no lights on the 4WD selector switch. I take this to mean the new module needs to be flashed to the truck. There is a YouTube post where the tech. uses a scan tool to program the module to the truck using the part no. of the module and the RPO code from the label in the glove box.

I have an appointment with a local shop on the 18th to have the module programmed.

 

It's fixed! The TCCM module was not the issue. It was the transfer case encoder motor. I put some paint marks on the gear and housing to mark the position of the gear and and applied battery voltage to the A & B terminals (orange and light tan wires on the row nearest to the connector latch - the outboard two terminals through a fused jumper and the motor did not rotate. Connecting the wires in the opposite polarity and the gear didn't rotate either.

What should have happened is the encoder gear should have rotated in one direction, and then the opposite direction when the power supply wires were interchanged but nothing happened.

A new encoder motor fixed the problem and I now have operating 4WD in 4Hi, 4Lo, AUTO, and back to 2Hi.

 

Straight up, man! Glad to hear it!!!

I installed RTV sealant all around the area where the encoder motor touches the T-C, and dilithium electrical grease in the electrical input. Haven't had to touch it yet.