* EL-49741 - 9 V+ Power Source Harness
* EL-49742 - Battery Voltage B+ and Ground Source Harness
* J 35616 - GM-Approved Terminal Test Kit
Circuit/System Verification
Key ON, engine OFF. The TCCM runs a 2 second bulb test on all indicators of the TCSCS at key ON.
Circuit/System Testing
Note: When test probing harness terminals, it is imperative to use the proper test probe from the most current version of the J 35616 - GM
terminal test kit. Use of an improper test probe may deform the terminal, resulting in intermittent open conditions.
1. Remove key. Disconnect the X1 connector at the transfer case shift control switch (TCSCS).
2. Door, open, key ON, engine OFF. Using the L-BU probe J 35616-64B, test for a diagnostic B+ (+0.0/-1.0 V) between the indicator dimming
control circuit, TCSCS X1 pin 4 and a good ground, such as the ground terminal of the EL-49742 - harness, black terminal.
锟斤拷 If the voltage is less than the specified range, test the affected circuit for an open/high resistance, short to ground or short to voltage. If all
circuits and connections test normal, test the body control module (BCM) for proper operation.
3. Using the L-BU probes J 35616-64B, test for a diagnostic B+ (+0.0/-1.0 V) between the indicator dimming control circuit, TCSCS X1 pin 4
and the 4WD HI indicator control circuit, TSCSC X1 pin 9.
锟斤拷 If the voltage is less than the specified range, test the 4WD HI indicator control circuit for an open/high resistance or short to power. If all
circuits and connections test normal, test the TCCM for proper operation.
4. Key OFF. Using the L-BU probe J 35616-64B, test for greater than 10 ohm between the indicator dimming control circuit, TCSCS X1 pin 4
and all other pins of the TCSCS X1.
锟斤拷 If the resistance is less than the specified range, test the affected circuits for a shorted together condition. If all circuits and connections test
normal, test the TCCM for proper operation.
5. Using the L-BU probe J 35616-64B, test for greater than 10 ohm between the 4WD HI indicator control circuit, TCSCS X1 pin 9 and all other
pins of the TCSCS X1.
锟斤拷 If the resistance is less than the specified range, test the affected circuits for a shorted together condition. If all circuits and connections test
normal, test the TCCM for proper operation.
6. Test the TCSCS for proper operation.
Component Testing
BCM
1. Key OFF. Disconnect the X1 connector at the TCSCS.
2. Using the L-BU probe J 35616-64B, connect a test light between the indicator dimming control circuit, TCSCS harness X1 pin 4 and a good
ground.
3. Key ON, engine OFF. The test light should be dull or OFF.
锟斤拷 If the test light is bright, test the indicator dimming control circuit for a short to voltage condition. If all circuits and connections test
normal, replace the BCM.
Note: When the DRL sensor turns the headlights OFF the indicator dimming control circuit voltage, TCSCS X1 pin 4, will go from a
diagnostic B+ to a true B+.
4. Place a shop light on the DRL sensor. When the headlights go out the test light should illuminate brightly.
锟斤拷 If the test light is dull or OFF, test the indicator dimming control circuit for an open/high resistance or short to ground condition. If all
circuits and connections test normal, replace the BCM.
TCCM
1. Key OFF. Disconnect the X1 connector at the TCSCS.
2. Key ON, engine OFF.
3. Using the L-BU probe J 35616-64B, test for 4.5-5.5 V between the 5-volt reference circuit, TCSCS harness X1 pin 11 and a good ground.
锟斤拷 If the voltage is greater than the specified range, test the 5-volt reference circuit for a short to voltage. If all circuits and connections test
normal, replace the TCCM.
锟斤拷 If the voltage is less than the specified range, test the 5-volt reference circuit for an open/high resistance or short to ground. If all circuits
and connections test normal, replace the TCCM.
