4 X 4 problem different twist

I have read everyones threads on different transfer case problems etc they all seem to hint at what i have but i cant pinpoint wether it is a vacume problem or a TCCM problem. Here is a little history.

About a week ago while driving the vehicle it automatically switched into 4x4 mode from 4 hi to 4 lo and to auto 4wd back and forth. I could get it to switch out but eventually it would start to auto switch back and forth. I got a new dash switch and put that in but that did not fix the problem. Then yesterday it went into auto 4 wd and will not come out anymore. every once in a while the service 4 wd will come on but then go off. Does this seem like a vacume problem or a computer TCCM problem. Is there a good way to check to see what path to proceede down first? Any help would be greatly appreciated before i break down and carry it to a dealer.

Welcome to AF

What year and what engine and mileage and what transfer case.
The newer transfer case shifting can be code checked and tested and checked with a transmission /transfer case capable scanner.

Unless you have one it is a good repair shop or dealer to get it tested.
Get codes and post back codes.

Also run a search on here for that problem.
MT

The trouble code is b2725 (active transfer case mode switch default) the scanner also said to remove a fuse to re-establish communication but could not find the fuse it was talking about.

Check you PM mail for the repair flow chart for that code on a 2001.
YOU FORGOT TO GIVE US THE YEAR AND ENGINE AND TRANSFER CASE AND MILEAGE.
MT

2001 Chevy Blazer 4.3 Liter Engine And The 4 Switch Np Transfer Case And 91000 Miles.

2001 Chevy Blazer 4.3 Liter Engine And The 4 Switch Np Transfer Case And 91000 Miles.

Transfer case ID tag is on the back of it.

Has it ever been serviced?
What kind of fluid used in it?
Does the push button switch have a automatic 4W button or just 2W and 4WH and 4W low and or N button?

Has it ever been serviced? No just the fluid changed.
What kind of fluid used in it? autotrac
Does the push button switch have a automatic 4W button or just 2W and 4WH and 4W low and or N button? four buttons.

I talked with the mechanic that read my code and he told me that he has had two in the shop in the last couple of years and it ended up being the TCCM or the switch. Since i already replaced the switch with no help I ordered a used TCCM from the same make and model year and will install that when it gets in and will take it to the GM dealer and get it programed.

do you think its a fluid problem?

What was the code no?

I do not think the TCCM needs re programed.
If the fluid has been serviced with the auto trac fluid the fluid it should be OK.
But there is certain problems and a TSB on some that the fluid needs changed and drove and re changed.

the code was B2725 (active transfer case mode switch fault)
They sympton was auto switching to 4 wheel hi and Lo and auto mode now it is just stuck in auto mode and wont switch out. You think replacing the fluid again would unjam it?

No on fluid change.
The code is for a selector switch or wiring or circuit bad.
You need to get a repair flow chart for that code and go threw the repair flow chart.
Run the voltage check on switch.
MT

had a similar problem with my 99 , turned out to be the front shift cable, under the battery. cable was $36.00 from the dealer.
DTC B2725 ATC Mode Switch Circuit Malfunction

Could be the TCCM or mositure in the connector. Then have you removed the battery cable for 30 min to reset the TCCM and see if that allows you to get back to 2Hi yet. See the How To section on all the parts in the 4wd system.

I will remove the tccm and spray the connector with wire dryer and i will remove the battery cable and see if that helps i will post the results

I replaced the TCCM with a used one for 100.00 and it fixed the problem switches with no problem at all. One question do i need to get the thing programmed at the dealership? All the mechanics said if it was that i was going to have to take it to the dealership to get it programmed?

I replaced the TCCM with a used one for 100.00 and it fixed the problem switches with no problem at all. One question do i need to get the thing programmed at the dealership? All the mechanics said if it was that i was going to have to take it to the dealership to get it programmed?

No.
Did you not read post no 8?
MT

Yeah i did read post #8 but what i was referring to is when i was on my little journey here to fix the problem several said that if it ended up being the TCCM after it was replaced then needed to hook the vehicle up to a little computer that costs $30,000 and program the new TCCM with the vehicles VIN and axel codes/ratios etc. The 4X4 works fine now but i want to know if what they said had any validity and if i don't get it done will that cause more damage down the road?

Yeah i did read post #8 but what i was referring to is when i was on my little journey here to fix the problem several said that if it ended up being the TCCM after it was replaced then needed to hook the vehicle up to a little computer that costs $30,000 and program the new TCCM with the vehicles VIN and axel codes/ratios etc. The 4X4 works fine now but i want to know if what they said had any validity and if i don't get it done will that cause more damage down the road?

As said I do not know of any programing on the TCCM.
Programing is just on the VCM/PCM. The engine and transmission computer.
But to confirm give your dealer a call.
Good Luck
MT

I did read post #8 but i was referring to the conversations of when the TCCM gets replaced new or used that i would have to take it to a dealership and they would have to program the TCCM with my vin number axel ratio's etc for 200.00
the 4x4 system works fine now but no getting it programmed with my vin etc will that ruin the vehicle down the road.

ignore post, it was a double problems with computer. I did call and they said they suggest it. So i will take it down there thank you for your help.

ignore post, it was a double problems with computer. I did call and they said they suggest it. So i will take it down there thank you for your help.

Let us know how that goes.
Unless they can figure out how to put a E Prom in the TCCM they are going to have a hard time trying to reprogram it.:grinyes:
MT