4WD not working and lights blink

[badpoor]

When I try to put it in 4low or 4high I can hear it try to engage and then disengage. The light on the switch blinks either 4low or 4high until I hear the disengage sound.
Could that be the vacuum actuator?

[old_master]

What year is the vehicle?
3 or 4 buttons on the dash switch?

[badpoor]

Originally Posted by old_master

What year is the vehicle?
3 or 4 buttons on the dash switch?

It's a 98 LT Three bottons 2hi 4hi 4low

[old_master]

When you select 4WD HI at the dash switch, the Transfer Case Control Module, (TCCM) checks the Wheel Speed Sensors, (WSS) and the Vehicle Speed Sensor, (VSS) to make sure all wheels are turning at the same speed, (no slippage). Then it commands the encoder motor on the transfer case to shift into 4WD HI. When the linkage inside the transfer case shifts, it operates a vacuum switch that sends manifold vacuum to the actuator under the battery tray. The actuator pulls a cable that operates a clutch mechanism inside the right front axle tube. When the clutch fully engages the axle to the differential, it operates a switch on the axle tube which confirms 4WD to the TCCM, and away you go! If any one of those things fail to report correctly to the TCCM, the TCCM commands the encoder motor to shift back to 2WD HI.

It sounds like your encoder motor is at least trying to shift but, the problem you're experiencing could still be any one of a number of things. A quick, easy check is make sure there's good vacuum at the actuator when shifted to 4WD with the engine at idle. Make sure the cable pulls in about a half inch, maybe three quarters tops. Post your results.

[badpoor]

The hood wont come up now and sometimes the lights where the switch is do not work at all.

[old_master]

Corrosion build up on the TCCM connector has been a problem. The TCCM is located behind the passenger side kick panel. Unplug the connector and check for corrosion and carefully clean the pins and sockets with spray electrical cleaner.

[badpoor]

Will do. Thanks I'll keep you posted on the outcome.
Sorry its taken so long to get back to you.

[badpoor]

I did the cleaning with eletric cleaner spray. Still nothing. That noise I described is actually comming from that TCCM,IT sounds like a bad flasher.

[old_master]

Can your hear the transfer case trying to shift, or is it just the TCCM clicking?

[badpoor]

Originally Posted by old_master

Can your hear the transfer case trying to shift, or is it just the TCCM clicking?

Just the TCCM is clicking.

[old_master]

The diagnostic trouble codes are displayed on the three transfer case shift select buttons. When pin 13 of the data link connector is grounded and the ignition switch has been in the OFF position for at least five seconds prior to positioning the ignition switch to the RUN position, the shift select buttons will blink to indicate a diagnostic trouble code from 1 to 4.
Position the ignition switch to OFF.
Make sure the ignition switch is OFF for at least 5 seconds.
Connect pin 13 on the data link connector to a vehicle ground source.
The data link connector is located under the instrument panel on the drivers side.
Turn the ignition switch to RUN. The shift select buttons blink indicating the codes. If the shift select buttons all blink one time and stop, no fault codes are stored in the TCCM. 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 second delay, the next code will blink. This sequence will continue until pin 13 is no longer grounded. When reading the diagnostic trouble codes, the number of shift select button blinks will indicate the code number.