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johnt, ASE Certified Technician
Category: Chevy
Satisfied Customers: 85
Experience:  27 years experience foreign and domestic
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My 1998 Chevy S10 pickup wont shift into 4 high. What do I check?

Resolved Question:

My 1998 Chevy S10 pickup won't shift into 4 high. What do I check?
Submitted: 6 years ago.
Category: Chevy
Expert:  johnt replied 6 years ago.

The most likely cause is the encoder on the transfer case. The following is from a

gm service bullitin. Just so happens , I just replaced one today on a 98 gmc jimmy.


Check the codes in the TCCM using normal diagnostic procedures. Codes can be checked by grounding an Orange wire. This will either be a 6 inch wire coming from the TCCM (some 1994 and 1995 models). If this has the 12 pin connector, then jump the Orange wire at pin J to ground. If this has the 16 pin connector, then jump the Orange wire at pin 13 to ground. Trouble codes are displayed by a flashing light on the selector switch. If there is a code 2 in memory, check the wiring from the TCCM to the encoder/motor assembly. At the encoder motor connector with the connector disconnected, there should be 5 volts on each of the following wires. Brown White, Dark Blue White, Yellow Black and Red White. The Black White wire should be a good ground back through the TCCM. If the wiring checks OK, replace the motor/encoder assembly. The code 2 in memory must be cleared after all repairs for the 4WD high range to work properly. To clear codes, remove the 10 amp CTSY lamp fuse and 10 amp ATC fuse for a minimum of 60 seconds. After reinstalling the fuse, cycle the ignition key on and back off 5 times. Now the shifts should take place for awhile from 2 Hi to 4 Hi. This will give one a chance to check the operation of the switches in the encoder motor assembly.

Customer: replied 6 years ago.
Where is the encoder located? Is this a computer diagnostic or a part to buy? I read to replace the transactual switch, another said the actuater under the battery. Hooha or no? Thanks for any advice, got your back w/ payment
Expert:  johnt replied 6 years ago.

The encoder is located on the left side of the transfer case , it is a part . Basically it is

an electric motor that shifts the transfer case. If you follow the information from my last

post you should be able to verify that this is the bad part. This is the most common part

to fail and cause the problem you describe.

Customer: replied 6 years ago.
I'm out of work in WI your answer could put food on the table. Thank you.
Expert:  johnt replied 6 years ago.
your welcome.
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