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frank
frank, Chevrolet Technician
Category: Chevy
Satisfied Customers: 3420
Experience:  33 years experience,24 years of Chevroler/GM experience and training .ASE Recertified Master Tech,
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2002 Chevy Trailblazer: the 4-wheel drive..engaging..dashboard..GM

Resolved Question:

2002 Chevy Trailblazer - we had an issue with the 4-wheel drive not engaging, thought it was the dashboard activator switch. Took it to the dealer, it wasn''t the switch. They called GM, had to "ping" something to get it to work, advised we might need a new encoder motor. Got it back, next day we were hearing a "clicking" noise in the front end. Fooled around with the switch. As long as we ran in 4-wheel high, no noise. Mechanic friend advised to unhook the encoder motor, making sure we were in 2-wheel drive. Switched to 2-wheel drive. With some difficulty reaching the connector, got it unhooked. Took it for a drive. Now it makes noise irregardless of where the setting is and obviously no lights on switch to indicate if it''s in 2-wheel drive. Looking for some guidance.
thanks
frustrated in Vermont with no 4-wheel drive
Submitted: 8 years ago.
Category: Chevy
Expert:  frank replied 8 years ago.
They transfer case module willset a code with a fault-it there is no code and the switch indicator bulbs are out,the transfer case module has a logic lock up.You pull the atc fuse under the hood for 1 minute and reinsert it.If a c0550 sets you need a transfer case module,Once you get the transfer case to shift you can diagnose the next problem,The encoder basically replaced the hand lever to shift it-the position sensors go bad in it along with the lock that holds it in a range-the front axle has a actuator that the module command s on in auto or 4x ranges.As it is you have a control issue and after disconneting and playing with things a second problem has occured that may correct itself once you get things to function correctly.
Customer: replied 8 years ago.
Reply to frank's Post: So, do I need to plug the encoder motor back into the system before I pull the fuse? I was trying to allow it to stay in 4-wheel drive until we could afford to have the motor replaced.
Is the motor replacement something that can be done without a diagnostics check? I don't have a unit to check codes.
Expert:  frank replied 8 years ago.
The most comon problem is the control module and the replacement has to be programed to you vehicle after replacement.Connect the encoder and pull the fuse-you are going to have to have acces to a scanner that can read the transfer case module codes.Doing anything with out reading codes could wind up costing you for a needless part and the encoders go for $600
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