99 Blazer 4x4 Not Working...

[LabRat116]

I just bought a 99 Blazer yesterday.

The Lights in the 4x4 Switch are NOT lit up. The 4x4 function does NOT work. There is no noise from the Encoder/Motor at all.

The Switch lights DO light up when the truck is turned on then go out after the diagnostic's test.

After driving a short while, the Service 4x4 light illuminates.

What do I need to do next ?

[LabRat116]

I took it to a local reputable tranny mechanic today who pulled the codes.

He got a Code B2725 which mentioned something about a Switch.

The mechanic was able to manipulate the transfer case into and out of 4x4 via the Code Scanner (pretty cool I thought!). So I know that the 4x4 components (actuator, encoder, motor and TCCM) are all working.

He said it most likely is a bad 4x4 Switch. He did mention that his scanner "should" have only been able to manipulate the Auto-Track (NP8) transfer case and not the NP1 transfer case. (Not certain his reasoning though....).

He was questioning whether or not someone "may" have installed the wrong switch. ???? Maybe installed this (3) button switch instead of the (4) button switch.

Now, he crawled under the truck and verified that it does in fact have an NP236 (NP8) transfer case underneath it.

Also, the Codes in the glove box do NOT show NP1. There only is an NP8 showing.

He mentioned it would be a significant under taking to change from a NP8 back down to an NP1. Different case sizes as well as different driveshaft lengths etc... So, that would NOT be likely a person changed from stock. ??

I'm thinking about just buying a new (4) button switch and see what happens ??

Ideas ???

[MT-2500]

Originally Posted by LabRat116

I took it to a local reputable tranny mechanic today who pulled the codes.

He got a Code B2725 which mentioned something about a Switch.

The mechanic was able to manipulate the transfer case into and out of 4x4 via the Code Scanner (pretty cool I thought!). So I know that the 4x4 components (actuator, encoder, motor and TCCM) are all working.

He said it most likely is a bad 4x4 Switch. He did mention that his scanner "should" have only been able to manipulate the Auto-Track (NP8) transfer case and not the NP1 transfer case. (Not certain his reasoning though....).

He was questioning whether or not someone "may" have installed the wrong switch. ???? Maybe installed this (3) button switch instead of the (4) button switch.

Now, he crawled under the truck and verified that it does in fact have an NP236 (NP8) transfer case underneath it.

Also, the Codes in the glove box do NOT show NP1. There only is an NP8 showing.

He mentioned it would be a significant under taking to change from a NP8 back down to an NP1. Different case sizes as well as different driveshaft lengths etc... So, that would NOT be likely a person changed from stock. ??

I'm thinking about just buying a new (4) button switch and see what happens ??

Ideas ???

B-2725 is a code for a bad switch on a 236 transfer case.

What does the ID tag on back of transfer case tell you about what transfer case it is?
If a 236 it needs the switch with the auto button on it.

[LabRat116]

Originally Posted by MT-2500

If a 236 it needs the switch with the auto button on it.

Yup. NV236.

I did replace the switch (with a new one) soon after I originally posted this. The problems remained.

I ended up replacing the Transfer Case Control Module (with a used one) and it cured my Blazer's woes!

I found out when nothing is making sense, it's usually the TCCM that is fried.

It was throwing out a FALSE B2725 Error code.