i have a 96 chevy s10 4wd blazer. My front axle won't engage with switch showing 4wd on. The back axle will grab and the front won't. The switch on the dash has been replaced. any suggestions would be great. thanks

 

tccm, encoder motor, actuator, vacuum problem. could be any of those

 

There is a little unit that monitors how the 2x 4x system is working. Take advantage of that system. See if there is a Diagnostic Trouble Code set. It is free to do;

Ground pin 13 of the OBD connector under the dash. Turn on the ignition key. If the lights on the 2X 4X panel blink ONCE and go off, there is no trouble code set. If there IS a trouble code, the lights will blink to indicate the number of the code.

count the number of the flashes and then check back here.

 

[/quote] Ground pin 13 of the OBD connector under the dash. Turn on the ignition key. If the lights on the 2X 4X panel blink ONCE and go off, there is no trouble code set. If there IS a trouble code, the lights will blink to indicate the number of the code.

count the number of the flashes and then check back here.[/quote]


how do you ground the pin?

 

I am having same problem with 4x4 not engaging. Which pin is 13. Thank you in advance for the help.

 

http://dl.dropbox.com/u/837001/OBD2/...tor-pinout.GIF

Here is a pic of the connector. I think in all the blazers they are installed as shown here.

You need to make a short jumper wire or use a paper clip. Connect pin 4 (chassis ground) to pin 13 (special uses GM 4X4 electrical, but non-automatic). Basicly, any Blazer with 3 button 4X4 control.

Leave the jumper in place and turn ON the key. The lights will blink ONE time and go out if you have no trouble codes. If a DTC does exist, it will blink a number of times and repeat.

1. 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.
2. 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.
3. When reading the diagnostic trouble codes, the number of shift select buttons blinks will indicate the code number.

Clearing Memory

Important: The codes will not clear if the 15-amp 4WD fuse is not removed for at least 30 seconds.
The code 1 will continue to occur until the ignition switch is cycled from RUN to OFF five times.

1. Perform the following in order to clear the Diagnostic Trouble Codes (DTC) and in order to clear the stored memory from the Transfer Case Control Module (TCCM) .
2. Turn the ignition switch to the OFF position.
3. Remove the 15-amp 4WD fuse.
4. Wait at least 40 seconds then replace the fuse.
5. Cycle the ignition switch from RUN to OFF five times in order to clear the diagnostic trouble code 1 from the TCCM.

-----------------------

If Error code "1" is indicated; This is referred to as "RAM standby power loss".

Check the Ctsy Lght fuse.

The transfer case shift control module normally has battery voltage supplied to it at all times through the battery positive voltage circuit (CKT 40). When the ignition is ON, the transfer case shift control module conducts a self-test to determine if it retains the same memory it had when the ignition was last turned OFF. This self-test indicates whether the RAM standby power supply to the transfer case shift control module pin C6 was interrupted, which would result in clearing DTC's from memory. If the self-test fails the transfer case shift control module sets DTC 1.

If Error code "2" is indicated; This is referred to as "Encoder Fault".

The TCEM (transfer case encoder motor) tells the TCSCM (transfer case shift control module) which possition it is in by means of the encoder which as 4 electrical sensors and 4 wires to the contol known as A, B, C and P. The controler puts 5 VDC on each and the transfer case grounds certain ones depending on it's possition.

When the controller gets voltages incorrectly, it sets a DTC-2. The problem will be in the TCEM, it's wiring, or thetransfer case shift control module.

If Error code "3" is indicated; This is referred to as "Motor Circuit"

The transfer case encoder motor has a bi-directional, permanent magnet, D.C. motor. When energized, the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, 2HI, and 4L ranges.
This DTC detects a short or open in the battery positive voltage circuit (CKT 1640), ground circuit, an internal short in the motor windings and related circuitry, or an internal transfer case shift control module failure.

Check for Batt+ on the TCSCM
Inspect the ATC 20A fuse
Verify Shift Control Module is well grounded
Verify Shift Control Module is providing 12 V to the shift motor +/- and -/+ when shift buttons are pushed appropriately

 

All of which is already posted in the Tech Article (DIY) section --> OBD2 NV233 Diagnostics along with a TON of other information pertinent to 4wd problems!

Also, billbobagns, please do not post multiple times in a row. Edit your post if you want to add more information. Consecutive posting is prohibited by the rules of the forum.