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Mazda Ed
Mazda Ed, Auto Service Technician
Category: Chevy
Satisfied Customers: 2223
Experience:  ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.
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1999 chevy blazer: 4hi..Found vaccum leak,now have 4 lo but not hi

Resolved Question:

1999 chevy blazer- no 4hi or 4 low. Found vaccum leak,now have 4 lo but not hi. Replaced 3 button switch with one that works no change. Replaced tccm with a good one,will now go into 4hi but to get back to 2hi car has to be moving and playing with button instead of from a stand still position
Submitted: 6 years ago.
Category: Chevy
Expert:  Mazda Ed replied 6 years ago.

HiCustomer

Try clearing the codes from the TCCM with the procedure below.

Diagnostic Trouble Code (DTC) Clearing

The transfer case shift control module is equipped with the ability to store diagnostic information which is useful to a technician in the event of a module, component or wiring failure. DTCs should not be cleared from the transfer case shift control module until these codes have been recorded or servicing the system has lead you to a repair and directed you to perform the "Clearing Flash Codes" operation. The following steps provide an easy way of clearing the flash codes properly.

  1. Turn OFF the ignition.
  2. Remove the 10 amp CTSY LP from the I/P fuse block, and the 20 amp ATC fuse from the underhood fuse block.

    Important: Replacing the fuse before the specified time may result in not clearing the DTCs.

  3. Wait a minimum of 60 seconds before replacing the fuse. Once the fuse is replaced DTC 1 will be set in the transfer case shift control module.
  4. Cycle the ignition switch from the OFF position to the RUN and back OFF five times in order to clear DTC 1 from the transfer case shift control module memory.
  5. Verify that the DTCs have all been cleared.

Then try operating the 4wd and check for stored codes with the procedure below:

Diagnostic Trouble Code (DTC) Displaying

The transfer case shift control module is equipped with the ability to store diagnostic information, which is useful to a technician in the event of module, component or wiring failures. This information can be retrieved from the transfer case shift control module by way of flash codes, which are displayed on the three transfer case shift control switch buttons. These buttons are located on the instrument panel to the right of the steering wheel Before obtaining DTCs, perform the following transfer case control module (TCCM) Self-Test.

TCCM Self-Test

  1. Observe the transfer case shift control switch indicators while turning the ignition switch to RUN. A properly operating system will flash all indicators and then will return to the current gear. If the system is operating normally, then proceed to Displaying Codes.
  2. If the TCCM failed the Self-Test, then test the following circuits.
    - Battery Positive Voltage (40 and 1640), and Ignition 3 Voltage for battery voltage
    - Ground Circuit for ground
    - Diagnostic enable circuit for an open or high resistance
    - Transfer case shift control switch connector
  3. If the above circuits are normal but the TCCM still fails the Self-Test, replace the TCCM.

DTC Displaying

  1. Turn OFF the ignition for 10 seconds.
  2. Connect PIN 13 on the data link cable (DLC) to a ground. The DLC is located in the cab under the instrument panel on the driver's side.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the transfer case shift control switch select buttons for flashing codes. Important: If the transfer case shift control switch buttons all blink only once and then stop, no fault codes are stored in the transfer case shift control module.

When one DTC is stored in memory, that code will blink that number of times followed by a 3 second pause and then repeat.
If more than one code is stored, the first code will blink, followed by a 3 second pause and then the second code will blink.
This sequence will continue until PIN 13 on the DLC is no longer grounded.
If the TCCM will not communicate the presence or absence of DTCs, test the above circuits in Self-Test Step 2. If the circuits are complete, then replace the TCCM.

Mazda Ed, Auto Service Technician
Category: Chevy
Satisfied Customers: 2223
Experience: ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.
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