Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC B0780 01: 4 Low Indicator Circuit Short to BatteryDTC B0780 06: 4 Low Indicator Circuit Short to Ground or Open
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
4 Low Indicator Circuit | DTC B0780 06 | DTC B0780 06 | DTC B0780 01 | -- |
Circuit/System Description
The 4 low indicator circuit consists of an interior lights dimming circuit and an 4 low indicator lamp control circuit. When the 4 low mode has been selected, current is supplied to the 4 low indicator lamp by the interior lights dimming circuit, traveling through the 4 low indicator lamp LED, at which time the transfer case shift control module supplies the ground through the 4 low indicator lamp control circuit.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | System voltage is 10-18 volts. |
Conditions for Setting the DTC
| • | The system monitors the voltage on the 4 low indicator control circuit. |
| • | If the system detects a voltage of 2 volts or less for 1.5 seconds when the 4 low indicator is not commanded, the DTC is logged. |
| • | If the system detects a voltage of 4.5 volts or more when the 4 low indicator is commanded, the DTC is logged. |
Action Taken When the DTC Sets
The SERVICE 4WD indicator is not commanded on for this DTC.
Conditions for Clearing the DTC
| • | The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault present. |
| • | History DTCs can be cleared using a scan tool. |
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Diagnostic Aids
A short to ground on the 4 low indicator control circuit will cause the 4 low indicator to remain on at all times. An open or high resistance will cause the 4 low indicator to be inoperative during the 2 second bulb check.
Circuit/System Testing
Check the interior dimming circuit pin 2 at the transfer case shift control switch for voltage for the 2 seconds after turning the ignition on during the bulb check.
| ⇒ | If less than battery voltage check the interior lights dimming circuit for an open or high resistance. If the voltage is low or non existent and the circuit tests good replace the BCM. If the interior dimming circuit and BCM test good go to the next step. |
| ⇒ | If the 4 low indicator is on at all times check the 4 low indicator control circuit for a short to ground. If the 4 low indicator is inoperative during bulb check, check the 4 high indicator control circuit for an open or high resistance or short to voltage. If the circuit checks good continue to the next step. |
| ⇒ | With the ignition on shift the transmission to neutral and using transfer case output controls attempt to command the 4 low indicator off and on. If the 4 low indicator is still inoperative short to 4 low indicator control to ground, if the 4 low indicator lights replace the module, program, and complete the motor learn procedure. If the 4 low indicator is still inoperative replace the switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for TCSCM replacement, setup, and programming |
