The 4WD drive always worked before. Now when I press the button to engage 4WD High you can hear something click over (Like it's working), but front wheels don't turn. If I switch it to 4WD Low the rear tires lock in at lower gear but still nothing from front wheels. I was told that it could be the
4WD switch. I bought one to replace it, but on the box it says "If defective, shifter light will indicate 2WD when shifted to 4WD". That is not the case though, my light shows that it's in 4WD High and 4WD Low, when I push the button to engage it. The lights on the sytem shows that it's working properly but i have no output from front wheels. Any suggestions before I change the 4WD switch and possibly find the problem not solved?
Have you tried to pull any stored codes? If not then here is what you do. Grab a short piece of wire or even a paper clip. Now look under the dash and find the ALDL connector. It will have 12 positions in it. They are laid out like this F E D C B A G H J K L M
You need to connect the upper right pin (pin A) to the third pin from the left in the bottom row (pin J) Now turn the key ON/RUN but not to START and watch the lights on the 4WD switch. After about 3 seconds they will flash the code if there is one. There are 4 codes you could see. Numbered 1,2,3,4 So code 2 would be Off-ON-ON-OffOffOff-ON-ON-OffOffOff until you turn off the key or pull the jumper. In the event there is more than one code it will flash them in sequence starting with the low code So a code 1 and 2 would be Off-ON-OffOffOff-ON-ON-OffOffOff-ON-OffOffOff-ON-ON and so on.
Code 1 is RAM Standby power lost: Common causes are changing the battery or blowing the TCCM Fuse.
Code 2 is Encoder Fault: This is the switch on the encoder motor itself, could be a break on the circuit board or the motor may have failed or it may not be moving properly.
Code 3 is TCCM Motor circuit: The motor control circuits are broken, Either a wire to the motor has grounded or broken or the motor itself has burnt out.
Code 4 is RAM/ROM Failure: This one can mean the TCCM itself has failed.
If you get a code. Write it down and then clear the code. To clear any TCCM codes you need to pull the TCCM fuse (should be a 5 amp fuse in the second row from the bottom in the fuse panel) Leave it out for 5 minutes. Now put it back in. Now check for codes again and you should find code 1. Pull the jumper and cycle the ignition 5 times off and on and the code 1 should clear. Now start the vehicle and check for proper operation again. IF it works now you probably have an intermittent problem in the encoder motor.
If it doesn't here is a way to narrow it down.
Jack it up and BLOCK IT with all 4 wheels off the ground. Now start it and engage 4wd. Shut it off and put the trans in park. Now go underneath and turn the front axle drive shaft.
IF it TURNS and the both front tires rotate the problem is likely in the transfer case. Either a broken chain or broken output shaft or the shift fork is bent/broken or the encoder motor is bad (common problem).
If it DOES NOT turn and you can rotate the right front tire and the left tire doesn't rotate the opposite way and at the same speed then either the front interlock fork has broken or the differential itself has a problem.
Open your hood and look where the battery is. Disconnect battery. Pull battery out. remove the plate/tray that holds the battery. Underneath this is a actuator (round looking thing with parts made of rubber). This(vacuum) is what pulls the cable to activate the front wheels. There is probably a rip in it. It is rubber. and when ripped the vacuuum won't hold to pull that cable
I have a 94 and had the exact same problem. the 4 wheel light would show it was engaged but wasn't really. Mine had a rip. new part from dealer was about 50 -75 bucks. replaced and all is good.
hth mike
newt> The 4WD drive always worked before. Now when I press the button to
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