12 Volt Under Voltage

12 VOLT UNDER VOLTAGE





For a complete wiring diagram refer to diagrams.
^ When Monitored:
Continuously with the ignition on.
^ Set Condition:
The Transfer Case Control Module detects the Fused B+ voltage drops below 9.0 volts for 2 seconds.

Possible Causes

- INTERMITTENT 12 VOLT UNDER VOLTAGE
- CHARGING SYSTEM DTCS PRESENT
- (A34) FUSED B+ CIRCUIT SHORT TO GROUND
- (A34) FUSED B+ CIRCUIT OPEN
- TRANSFER CASE CONTROL MODULE

1. CHARGING SYSTEM DTCS PRESENT
With the DRBIII read Engine DTCs.

Are there any Charging System related DTCs present?
Yes >>Refer to the symptom list and perform the appropriate diagnostic procedure(s) as necessary.
Perform TRANSFER CASE VERIFICATION TEST. Transfer Case Verification Test
No >>Go To 2

2. 12 VOLT UNDER VOLTAGE PRESENT
With the DRBIII read Transfer Case DTCs. Record all DTC information.
With the DRBIII erase Transfer Case DTCs.
Start the engine and cycle the Transfer Case Selector Switch through all positions.
With the DRBIII read Transfer Case DTCs.

Does the DRBIII display 12 VOLT UNDER VOLTAGE?
Yes >>Go To 3
No >>Go To 6

3. (A34) FUSED B+ CIRCUIT SHORT TO GROUND





Turn the ignition off to the lock position.
Disconnect the Transfer Case Control Module C3 harness connector.

NOTE: Check connectors - Clean/repair as necessary. Measure the resistance between ground and the Fused B+ circuit.

Is the resistance below 5.0 ohms?
Yes >>Repair the (A34) FUSED B+ CIRCUIT for a short to ground.
Perform TRANSFER CASE VERIFICATION TEST.Transfer Case Verification Test
No >>Go To 4

4. (A34) FUSED B+ CIRCUIT OPEN





Ignition on, engine not running.
Using a 12-volt test light connected to ground, check the (A34) FUSED B+ CIRCUIT at the Transfer Case Control Module C3 harness connector.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?
Yes >>Go To 5
No >>Repair the (A34) FUSED B+ CIRCUIT for an open circuit or high resistance. If the fuse is open, check the circuit for a short to ground.
Perform TRANSFER CASE VERIFICATION TEST.Transfer Case Verification Test

5. TRANSFER CASE CONTROL MODULE
Using the wiring diagram as a guide, inspect the wiring and connectors relative to this DTC. Inspect all power and ground circuits. Repair as necessary.
If there are no Charging System related DTCs or other possible causes remaining, view repair.

Repair
Replace the Transfer Case Control Module.
Perform TRANSFER CASE VERIFICATION TEST.Transfer Case Verification Test

6. INTERMITTENT WIRING AND CONNECTORS
The conditions necessary to set this DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle test the wiring harness and connectors while checking for shorted and open circuits.
Using the DRBIII monitor he data related to this circuit while performing the wiggle test. Look for the data to change or for the DTC to reset.

Were there any problems found?
Yes >>Repair as necessary.
Perform TRANSFER CASE VERIFICATION TEST.Transfer Case Verification Test
No >>Test Complete.