Transfercase codes

[HenryJ]

The diagnostic trouble codes are displayed on the three transfer case shift select buttons. The shift select buttons are located on the instrument panel when the connector pin 13 on the data link cable is grounded, and the ignition switch has been OFF for at least five seconds prior to positioning the ignition switch to run the shift select buttons will blink various times together in order to indicate a diagnostic trouble code from 1 to 4.
Position the ignition switch to OFF. Ensure the ignition switch is positioned to OFF for at least 6 seconds.
Connect pin 13 on the data link cable to a vehicle ground source. The data link connector is located in the cab under the instrument panel on the drivers side.
Position the ignition switch to RUN.
Note the shift select buttons for blinking codes. Refer to Diagnostic Trouble Codes .
If the shift select buttons all blink one time and stop, and do not continue to blink, no fault codes are stored in the TCCM.
The transfer case shift select buttons will blink in order to identify any stored DTC. If only one code is stored in the TCCM memory, that code will blink repeatedly with a three second delay between blinking sequences. If more than one code is stored, the first code will blink once, then after a three seconds delay, the next code will blink. This sequence will continue until pin 13 is no longer grounded.
When reading the diagnostic trouble codes, the number of shift select buttons blinks will indicate the code number.
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Diagnostic Trouble Code (DTC) 1
When the ignition switch is positioned to RUN the TCCM test to determine if RAM standby Power (maintained battery power) to the TCCM was lost since the ignition was last turned OFF. When power is interrupted on pin C6 of the TCCM, the TCCM stores a loss of RAM standby power.

Diagnostic Trouble Code (DTC) 2
During electronic shifting, the TCCM check the motor/encoder for normal operation. If the motor/encoder does not function correctly enough times, the TCCM stores a motor/encoder failure DTC 2.

Diagnostic Trouble Code (DTC) 3
The TCCM performs a test each time the electronic-shift motor is turned ON or OFF. If the motor does not function properly the TCCM stores a motor circuit failure DTC 3, and the shift select buttons blink in order to inform the driver of a problem.

Diagnostic Trouble Code (DTC) 4
Each time the ignition is turned ON, the TCCM tests the memory, the program, and the internal system in order to ensure that the TCCM is operating properly. If the TCCM detects a fault within the TCCM, the TCCM stores a RAM/ROM memory failure (DTC) 4.

When the TCCM is running a diagnostic, and a code 4 is displayed by the shift select buttons, replace the TCCM.

Electronic 4x4

What is wrong, How to fix, How to install

***HOW TO CHECK WHAT IS WRONG***

You will probably know when your 4x4 has failed when you needed it in the mud pit. Mine, for instance, failed by not doing anything when I hit the 4HI button. However, it would go into 4LO.

To read the codes for the 4x4 with electric shift transfer case, install a jumper wire from terminals "J" and "A" on the ALDL (12 pin connector under the driver's side dash)

The lights on the 4x4 indicator (switch) will flash in a pattern, there are only 4 codes, one flash is code one, 2 flashes is a code 2, and so on...

Code "1" is "RAM standby power" and is considered normal, may be caused by clearing the codes.
Code "2" is "Encoder fault"
Code "3" is "TCCM motor circuit"
Code "4" is "RAM/ROM failure"

If you have the codes 2 or 3 check all the encoder motor connections at the transfer case, if OK it will need a new encoder motor assembly.
If you have code 4, replace the TCCM.

Make sure all connections are good and no corrosion, and then it's either an encoder or TCCM.

***TO FIX THE TCCM***

The TCCM is located behind the glove box, and is accessed from underneath the dash. To remove, the kick panel and black cover come off. Then a 1/4" screw holds the "brains" in the dash. The middle computer is the Truck's brain, the one on the backside is the TCCM, and on the front is the small ABS computer. Simply loosen the 2 10mm nuts on each side, and they will separate.


***WAYS TO FIX THE ENCODER MOTOR PROBLEM.***

This is the most common problem, and was my problem.

Cheap way - To clear the codes and reset the computer, pull the 5 amp TCCM fuse, located at the bottom of the fuse box. Wait at least a half hour, and then replace the fuse. Turn the ignition key to run, wait for the 4x4 lights to blink, and then turn off. Repeat 5 times, and then start the truck.

Decent price way - I just went and bought a rebuilt encoder motor from a company off of Ebay. Their company is http://www.northernautoparts.com The part cost me around $140 with a 1 year warranty and $38 core refund when I send the old one back.

Expensive way - buy a brand new one from GM for over $300.

***HOW TO INSTALL THE NEW ENCODER MOTOR***

Lucky way - Only thing that needs to be removed is the encoder motor itself. Tools needed are a 10mm hand wrench and a 8mm and 10mm socket wrench. The 10mm socket will work on the upper and lower bolts, while the regular wrench is needed for the middle bolt. (Tight squeeze). The 8mm socket is for the electric plug.
Then, just pull out, and wiggle it out of the truck. Install in reverse order.

Unlucky way - This means the encoder motor did not just wiggle out. Now the front drive shaft will have to be removed at the transfer case. Then, a yolk puller is needed in order to remove the yolk from the transfer case. Once this is done, go to the directions in lucky way.

Writeup by gmshades

Encoder Signal Check

The Transfer Case Control Module (TCCM) checks the encoder signal in order to verify that the transfer case is in either 2HI, 4HI, or 4LO.

Encoder Switch Monitor Check

While the transfer case shifts, the encoder within the electric-shift motor is monitored for the proper operating sequence. If during a shift, the encoder changes to an incorrect position, an error counter in the Transfer Case Control Module (TCCM) starts to count the number of times the encoder fails. If the encoder fails eight times, the TCCM produces a Diagnostic Trouble Code (DTC) of 2 indicating an Encoder Fault. When this happens, the TCCM outputs a signal in order to default the rail shift pattern in the encoder in order to allow for only shifts into 2HI and 4LO.
In order to protect against transient, random encoder faults caused by vibration, contamination, electrical noise, etc., the error counter reduces the count by one each time a good encoder value is detected. The encoder must fail 25 percent of the time for the TCCM to store a DTC of 2 and indicate a damaged encoder.

Motor and Relay Voltage Checks

Whenever the electric-shift motor is turned ON or OFF the motor and the electrical circuits are tested both in the de-energized and energized condition. If one or both voltage relays fail to detect the proper voltage after energizing or de-energized and energized condition. If one or both of the voltage relays fail to detect the proper voltage after energizing or de-energizing, the shift is aborted by the Transfer Case Control Module (TCCM) and a Diagnostic Trouble Codes (DTC) of 3 is stored in order to indicate a faulty TCCM motor circuit. If one or both relays fail to detect the proper voltage after de-energizing, both relays are turned ON by the TCCM, (even with the ignition switch positioned OFF) in order to prevent the motor from running. The TCCM then stores a DTC of 3 in order to indicate a faulty TCCM motor circuit. All of the status lamps blink three times, stop, and repeat the blinking continuously in order to alert the driver that the electronic shift system requires immediate repair. The battery. will drain when this condition occurs, regardless of the ignition switch position.

Motor/Encoder Circuit Operation

The Transfer Code Control Module (TCCM) operates the motor/encoder in one direction by energizing one relay while the second relay is de-energized. The TCCM operates the motor in the reverse direction by energizing the second relay while the first relay is de-energized. The encoder part of the motor/encoder sends shift positioning signals to the TCCM. The motor/encoder converts a shaft position, representing a mode of range selection, into electrical signals for use by the TCCM. By interpreting the four channels (P, A, B, C) of the encoder, the transfer case control module can detect what position the transfer case is in 2HI, 4HI, 4LO, or in transition between any of the two. The four hall effect sensors of the motor/encoder are used for channels (A, B, C, and P). These sensors provide a path to ground when a magnet passes over them. A rotating magnetic ring causes the hall effect sensors voltage to drop from 5 to 0 volts. The TCCM detects the voltage of all the channels and interprets the current transfer case shift position.

Hey BTW I found this info, I know your getting code 3... may worry u a little..


3 - TCCM motor circuit : Basically, every time the TCCM is powered up, it test the encoder motor. If something isn't right, it'll trip the code 3.
Possible causes
1. Open or shorted circuit between encoder motor and TCCM
2. Short/open connection in the motor itself
3. Malfunctioning motor relay
(this can cause the indicator lights to flash all the time (normal driving). If this happens, it must be fixed IMMEDIATELY. It can cause encoder motor failure even when the ignition is off)

[killian96ss]

Very good info! This would be a good sticky!

Steve

[snowsurfer]

You guys are great!!!! Prior to reading all this helpful info I called the local dealer and priced a TCCM module!!! Yikes!!!! 360.00 and change...He recommended I bring the truck down since electrical parts are non refundable and this may not be the problem.....
I will try your diagnostic proceedurs tomorrow when I get off work...
Couple questions....Are you talking about grounding the #13 pin from the obd2 connection point? If so which one is #13?

I actually only put the truck in 4wd about 5 times in the last 2 years since getting the truck. It's a cruise truck, didn't really need a 4wd but that's all they had here in a crew.

I'm an old school guy, hate all these electronics....

Thanks for the help guys...


Aloha

[HenryJ]

The pins are numbered as you are facing the connector , numbered left to right starting at the top. 1-8 on the top row.
The bottom row is numbered 9-16
1- not used
2- Class 2 serial data
3- Not used
4- Ground
4- Ground
6-12- not used
13- Diagnostic Enable
14-15- not used
16- Positive battery voltage

(information from 2001 Helms)

On the bottom row confirm the location of the positive feed #16. There is conflicting information in the manuals as to the numbering sequence being left to right or the reverse.

The above diagnostic procedures are for first gen diagnostics, however the procedure may work for second gen? The pin to be grounded may be different though.

I have not tried or tested this on mine yet.

[snowsurfer]

Thanks again, this is the OBD2 connect point correct?

[killian96ss]

Thanks again, this is the OBD2 connect point correct?

Yes!

Steve

[rlrnr53]

After reading through this thread, it all sounds familiar. I recently purchased a 2001 crew after a head on collision totaled my 96 S-10 Extended cab. A crew is the only truck that will meet our needs. After getting the truck home, I discovered that the only way to get into 4-hi is to stop, put the transmission in neutral, then hold the 4-lo button in until it goes in 4-lo, then hold the 4-hi button in until the lights quit flashing and then if I'm lucky it wil go in 4-hi. To go to 2-hi I have to repeat the procedure in reverse. I'm hoping the diagnostics here will help. I've already replaced the transfer case switch just to be on the safe side. I enjoy reading the posts here, they are very informative. Thanks for all the info.

[killian96ss]

I found a TSB that indicates 75% of all TCCM's replaced are not defective and should only be replaced if they are storing DTC C0550, or there is no communication with the scan tool. Here is the info.

Bulletin No.: 05-04-21-002

Date: March 10, 2005

INFORMATION

Subject:
Guidelines for Replacement of Transfer Case Control Module (TCCM)

Models:
2005 and Prior Light Duty Trucks

with New Venture Gear (NVG) Transfer Case (RPOs NP1, NP4, NP8)

Dealers are replacing the TCCM unnecessarily.

Dealers are replacing the TCCM with codes stored in HISTORY only. The TCCM does not have a current fault condition when tested.

Parts reviewed at the Warranty Parts Center (WPC) have a 75% No Trouble Found (NTF) rate. The only two legitimate reasons to replace the TCCM are:

^ Diagnostic Trouble Code (DTC) C0550

^ NO Communication with a scan tool.


DTC C0550

This DTC indicates that the module has an internal fault and should be replaced.

No Communication

^ The no communication conditions referenced here are also caused by a module internal fault to a point where the module physically will not talk. A technician cannot pull DTCs from the module because it will not communicate. The module is electrically dead.

^ No communication is not to be confused with a U1026 code. This code tells the technician that the module may still be functioning but is temporarily off line. This code may be set by the Instrument Panel (IP) or the Powertrain Control Module (PCM) against the TCCM. The technician needs to figure out why the module went off line. These are typically caused by connection concerns. There is no need to replace a TCCM for a U1026 DTC.


Diagnostic Aids

^ When diagnosing a transfer case electrical control system, ALWAYS check power and ground wiring first.

^ Test the connections for intermittent or poor connections, complete plug insertion, bent pins, pushed out terminals and water contamination.


Pay particular attention to the terminal connections at the module. Spread or open terminal connections may create an intermittent contact. Do a pin drag test. Refer to the terminal testing information in the table shown.

^ After repairs are complete, ALWAYS clear DTCs from the module prior to a system function test. If codes are not cleared first, the system will not function after repair. The technician may erroneously think that the system is still down and that further repairs are needed.


Warranty

Dealers who unnecessarily replace the TCCM that are found to have No Trouble Found (NTF) at the WPC will be returned to the AVM (Area Service Manager), or the DSM (District Service Manager) in Canada, through the Regional Feedback Process and may be charged back for the repair through the WINS system.

Steve

[green02crew]

Well my 4wd hi just quit today so I only have 4 low and 2 hi. Perfect timing since we just got a foot of snow yesterday. I hit 4hi and the lights blink a few times and then goes back into 2 hi. So to get out of the snow I resorted to using 4lo which thankfully still operated. Now pressing the 4hi button does nothing, not even a flash of lights. It just stays in 2hi.

It had done this before and I unplugged the battery and waited a min and plugged it back in. Worked normally for a couple weeks. Back to doing it again. I checked and it gives a code 2.

I was trying to do the method of clearing the codes by pulling the 5 amp fuse but there isn't one. There is no 5 amp fuse that I could find either in the under hood box or by the drivers door.

So down to the questions: Is there another way to clear the codes? Clearly the problem is persistent as I had unplugged the battery before and it came back. Is unplugging the battery the same as it would be pulling this fuse? Or should I just start searching the junkyards for an encoder motor? I can see this getting expensive...

[rlrnr53]

It may sound silly, but Ihave had the same problem with my 01. The way I have corrected the problem on more than one occasion is to remove the courtesy light fuse for a few hours (usually overnight). I know it sounds crazy, but it works for me.

[green02crew]

That does sound like an interesting fix but whatever works I guess! Perhaps the TCCM is on the same fuse as the courtesy lights? That would be more convenient than unplugging the battery each time and resetting all electronics. Do you happen to know which fuse that is so I may test that out? Either way I'd like to find a permanent fix rather than resetting it every 3rd time I try to use the 4wd. I get 2 good uses out of it and then error.

[daevans315]

I just replaced my encoder motor and wanted to throw a couple hints:

1. My encoder would not wiggle off the transfer case easily. It was hanging on the front drive shaft yoke. After some swearing I looked at the new one going in and one of the plastic reinforcing webs that the old one was hanging up on was designed very different. 30 seconds with the hot knife to modify the old one to look like the new one and it came right out. The autoparts guys didn't bat a eye at the 'modified' core.

2. After putting it all back together it behaved exactly as before (4 low only) I had pulled the 4wd fuse for the time it took to do the job so I assumed the codes were cleared. However it took pulling the battery for 30 mins to clear my codes for some reason. After that.. all is well.

[F9K9]

Was the replacement delco or aftermarket. Good info. Thanks!

[YellowCrewCabber]

My truck has had issues with it not going into 4 HI. A dealer said it was the selector switch. I told them they were wrong. They replaced it anyway. It quit working again in less than two weeks. I didn't bother with it for months. I had mentioned it on a motocycle forum in the off topic section almost a year ago now and this was my answer.
FYI Encoder motors don't normally go bad. Sometimes there are componets that get moisture inside them corrode including the encoder motor. Usually can be fixed by dissasembly and cleaning. But this is what fixed mine:
1. Turn all accessories off.
2. Dissconnect the battery. (BOTH CABLES)
3. Turn the head lights and the key to the on position.
4. Hold the negative and positive battery cables together (grounding them) for 15 seconds.
5. Leave it this way for 1 hour. This is draining computer(s) memory and all redisual power.
6. Turn ignition and head lights off.
7. Reconnect battery.
8. Start engine. Let it run for three minutes.(IDLE ONLY) Do not turn anything on. During this 3 minutes your computer is resetting itself and "relearning".
9. Your 4 wheel drive should now work.

I have done this procedure twice and both times were sucessful.
You'll want to be in 2 wheel drive when you do this.

[daevans315]

Was the replacement delco or aftermarket. Good info. Thanks!

The replacement was a refurb' from O'Reilly Auto Parts. ~$150 after the core return. They were the cheapest in town. I found it for $125 online but O'Reily has a lifetime warranty on it.

[roadrunner]

YellowCrewCabber, I've experienced nearly every oddball thing that can and does go wrong with our electric 4x4 shift system. Yes encoder motors can and do fail. Perhaps more accurately most of the time the failure is in the switching assy that is part of the encoder assembly. I personally have had the 4Hi sensor portion fail. I can tell you from experience only having 4lo and 2hi really sucks when you need 4hi and it don't work.
While I applaud your resoursefulness you might have saved yourself a lot of time and work if you had pulled the right hand kick panel and unplugged the transfer case computer module located behind it for a few seconds. I too have tried fuse pulls etc with limited success but unhooking the controller as I've just described will restore 4x4 function. I've been told by another off site individual and some here have argued otherwise that the culprit in retaining memory in the control module is caused by the battery backup for the air bag system. It seems the wiring for the t-case module runs through there and it will keep the memory alive in the t-case controller thus preventing normal function restoration in many cases. Additionally no particular shift position is required for this procedure to work.
After doing this keep in mind your module keeps track of successful shifts versus unsuccessful ones. Each successful shift removes one unsuccessful from memory and vice versa. When you hit a preset number of bad shifts is when all the problems with loss of shift positions and abilities start. Kind of a lock-out type safety. What this means is you likely have another problem causing all those bad shift entries to occur and after enough are recorded your lock out will likely return and continue to do so until you locate and fix the cause.
Not throwing cold water. Just been there and done that.

[YellowCrewCabber]

Thank you. I will definately go that route next time I need to. I am pretty sure there is a problem causing this problem. I should find a good manual to understand how this system works. No offense taken.
Jeff

[roadrunner]

No offense was intended. Simply supplying information to possibly help you out with your problem learned from painful past experience.
As for manuals let me know if you ever find one with this information in it. As far as I know the only ones with useful information on this system are OEM. I recently went to Helm inc on the net and nearly fell off my chair when I saw the price. As near as I could tell it was on cd and covered all gm vehicles 98-08 @ $400.00. Much as I need and would like to have it that's out of my meager reach. At least for now.

[YellowCrewCabber]

No offense was intended. Simply supplying information to possibly help you out with your problem learned from painful past experience.
As for manuals let me know if you ever find one with this information in it. As far as I know the only ones with useful information on this system are OEM. I recently went to Helm inc on the net and nearly fell off my chair when I saw the price. As near as I could tell it was on cd and covered all gm vehicles 98-08 @ $400.00. Much as I need and would like to have it that's out of my meager reach. At least for now.

400 BUCKS!!!!! That's highway robbery. Maybe someone on KaZaa has it. If KaZaa is still around.

[roadrunner]

Let us know if you find the OEM on KaZaa or anywhere else for that matter. I as well as a few others would love to have it. And yeah, at that price I thought they should've had a pic of a gun pointed at me right by it. Or perhaps a shot of the buyer doing an ankle-grab exercise.

[jsulen]

Thanks for sharing your thoughts with us. I'll contact you guys when I am need of a part. Any idea where can I buy transfer case shift mode selector?

[HenryJ]

Thanks for sharing your thoughts with us. I'll contact you guys when I am need of a part. Any idea where can I buy transfer case shift mode selector?

Hmm? Asked and answered? Spammer?

A1 Cardone Transfer Case Motor
1999-2004 Chevrolet S10
A1 CARDONE TRANSFER CASE MOTOR, REMANUFACTURED -- This high quality and direct fit OE replacement transfer case motor has the precise amount of lubricant for quiet operation and long life, features 100 percent recharged motor magnets for OE performance and reliability, and has been 100 percent computer-tested for guaranteed performance; With A1 Cardone's limited 12-month or 18,000-mile warranty.
Fits: 4WD.
Condition: Remanufactured
Warranty: 1-year or 18,000-mile A1 Cardone limited warranty
Availability: In Stock

You might also check Rockauto.com , or better yet your local auto parts store. Support the businesses that keep your community alive.

[F9K9]

That struck me as odd this morning, as well.

[jeffns-10]

My dealer wants to change the switch and the transfer motor @ 1400. I think I will try this first.

[F9K9]

My dealer wants to change the switch and the transfer motor @ 1400. I think I will try this first.

Welcome to the forum and kudos to you for researching your problem.

[roadrunner]

Welcome to the forum. Let us know if we can be of any assistance in your repair situation.