Thanks for the reply. The entire switch itself is about a month old. All three lights light up every time when the ignition is turned to on for the test on startup thing like they're supposed to but the lights shut off after the quick test phase is done. Also, if the light was just burnt out wouldn't it still engage the 4WD?
The Main 4wd Components:
TCCM - Transfer Case Control Module - Located behind the glove box. This is the electronic brains behind the shifting.
Switch. The push button switch in the dash - driver input/indicator.
Encoder Motor is Located on the transfer case. This is what actually shifts the transfer case, and tells the TCCM what position it is in.
Vacuum Switch is also located on the transfer case. This is what sends vacuum to the vacuum actuator when the transfer care is in 4HI or 4LO.
Vacuum Actuator is Located under the battery tray. This is what engages or disengages the front driveshaft.
Front Axle Switch is Located on the front axle, This is what tells the TCCM when the front axle is engaged.
There are 2 types of shifts - mode shifts, and range shifts. A mode shift would be from 2HI to 4HI, and vise versa. A range shift would be in and out of 4LO. You can Mode shift any time when moving, but must be stopped in neutral to do a range shift.
Normal Operation: When the switch is pressed, the indicator light flashes, and the TCCM tells the encoder motor to move from its current position to the desired position. When the transfer case enters 4HI, it engages the vacuum switch to engage the front axle. The axle switch then tells the TCCM that it's engaged. Then the 4wd indicator light will come on. The transfer case has 3 positions. 2HI, 4HI, and 4LO, in that order. T he encoder motor senses which position it is in, and tells the TCCM definitively where the transfer case is.
Common problems:
Switch failure: Nothing works. Pushing either end causes NOTHING to actuate (No sound from dash or transfer case)
Encoder failure: Transfer case will not enter 4HI, but will enter 4LO. This is because the computer doesn't know exactly what position the case is in, so it just moves to either extreme (2HI or 4LO).
Vacuum actuator failure: Rubber diaphragm breaks. The transfer case changes position, but the front axle never engages. Takes an extended time for the indicator lights to come on.
Secondary problem list:
4wd does not engage:
Vacuum hoses deteriorated
Engine vacuum insufficient
Front axle actuator cable is kinked or seized
Faulty front axle vacuum actuator
Faulty transfer case vacuum switch
Faulty 4wd indicator lamp
Blown TCCM fuse
Bad electrical connections
Faulty switch
Faulty encoder motor
Faulty TCCM Faulty transfer case
Faulty front axle
4wd will not disengage:
Faulty wiring
Faulty lamp
Transfer case vacuum switch plugged or faulty
Vacuum lines pinched
Transfer case vent filter plugged
Actuator cable kinked or damaged
Faulty switch
Faulty encoder motor
Faulty TCCM
Faulty front axle
4wd disengages under load:
Insufficient vacuum
Vacuum system not venting properly
Transfer case noisy in all modes:
Low transfer case lube level
Internal transfer case problem
Noisy in 4LO:
Transfer case not completely engaged; disengage and re-engage it
Internal transfer case problem
Leaking from Transfer case vent:
Transfer case overfilled is often caused by the seal between the transfer case and transmission going bad.
Leaks at output shafts:
Transfer case overfilled
Vent hose plugged or kinked
Seals damaged
How to obtain diagnostic trouble codes:
For OBD1 vehicles with the push button above the light switches:
To read the codes for the push button shift transfer case 4wd system, install a jumper wire from terminals "J" and "A" on the ALDL (12 pin connector under the driver's side dash) - A is the top right pin and J is the third from the left on the bottom.
http://www.vanforum.net/Extern/Technik/Images/Bilder/Connector-1.jpg
Then the turn the ignition to run (DO NOT START). The 4wd indicator lights will self test, then go out. Then if any codes are stored they will flash. If more than one is stored, they will alternate flashes... for example:
flash - pause - flash flash flash - pause - flash - pause -flash flash flash
Would indicate codes 1 and 3...
The error codes are:
1 - RAM Standby Power Fault
2 - Encoder Fault
3 - TCCM Motor circuit
4 - Ram/Rom failure
1- Ram Standby power fault: Possible open connection or short in the TCCM fuse circuit. However, this code is often considered normal and may be caused by clearing the codes.
2 - Encoder fault: Every time the t-case position moves, the TCCM checks the encoders readings during the shift. If something isn't right, it will increment an error counter by 4. A successful reading decreases the counter by 1. If the counter reaches 32, the TCCM determines the encoder faulty, and bypasses 4hi. Check for loose wires and excessive dirt/moisture near all connectors.
3- TCCM (Transfer Case Control Module) motor circuit: Basically, every time the TCCM is powered up, it tests the encoder motor. If something isn't right, it will 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 IMEDIATELY. It can cause encoder motor failure even when the ignition is off.
4 - Ram/Rom failure: Internal software failure. Pull the TCCM fuse for 3 mins. Then replace it, and cycle the ignition from off to run 5 times. Then re-check the codes. If code 4 still is present, then the TCCM must be replaced.
Start with checking for the codes and we can go from there, keep me posted.
Thinks it the 74 bulb. Start with that and hope it's only the light bulb. Just use a flat head screw driver to work the center vent away from the dash so you can repalce the light bulb on the switch.