GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2001 🢒 S/T Isuzu - 4WD 🢒 DTC 🢒 DTC 001

Circuit Description

The transfer case shift control module normally has battery voltage supplied to it at all times through the battery positive voltage circuit (CKT 40). When the ignition is ON, the transfer case shift control module conducts a self-test to determine if it retains the same memory it had when the ignition was last turned OFF. This self-test indicates whether the RAM standby power supply to the transfer case shift control module pin C6 was interrupted, which would result in clearing DTC's from memory. If the self-test fails the transfer case shift control module sets DTC 1.

Conditions for Clearing the DTC

This DTC will clear when the voltage supply failure has been corrected and the ignition switch has been cycled five times.

Diagnostic Aids

When the vehicle is equipped with a manual transmission the clutch pedal must be depressed and working correctly in order for the transfer case to shift to the 4 low position. In order to confirm that it is operating correctly go the engine data 1 screen under the engine data display and observe the clutch pedal switch parameter.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step inspects the CTSY LP fuse for an open.

    2.

  2. This step test the battery positive voltage circuit (CKT 40) for an open or high resistance.

    3.

  3. This step rechecks the CTSY LP fuse for an open

    4.

  4. This step tests the battery positive voltage circuit (CKT 40) for a short to ground.

DTC 1 -- RAM Standby Power Loss

Step

Action

Value(s)

Yes

No

Schematic Reference: Transfer Case Control Schematics

1

Important: Check the transfer case shift control module for DTCs. The transfer case shift control module is not a class 2 device. DTCs are displayed on the transfer case shift control switch. Use the following four steps to obtain DTCs.

  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.

Did you perform A Diagnostic System Check - Transfer Case?

--

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

Important: This code can get set falsely due to the improper clearing of DTCs or replacement of a blown CTSY LP fuse.

Inspect the CTSY LP fuse for an open.

Was there a problem found?

--

Go to Step 4

Go to Step 3

3

Test the battery positive voltage circuit (CKT 40) for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 7

Go to Step 6

4

  1. Replace the fuse.
  2. Drive the vehicle under various road conditions and retest the fuse.

Did the fuse blow again?

--

Go to Step 5

Go to Step 7

5

Test the battery positive voltage circuit (CKT 40) for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 7

Go to Step 6

6

Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .

Did you complete the replacement?

--

Go to Step 7

--

7
  1. Clear all DTCs from memory. Refer to Diagnostic Trouble Code (DTC) Clearing .
  2. Operate the vehicle while pressing each of the buttons on the transfer case shift control switch.

Does the DTC reset?

--

Go to Step 2

System OK