* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC B0770 01
- AWD Indicator Circuit Short to Battery
DTC B0770 06
- AWD Indicator Circuit Short to Ground or Open
Diagnostic Fault Information
Circuit/System Description
The all wheel drive (AWD) indicator circuit consists of a light emitting diode (LED), a LED feed circuit and a LED control circuit. The indicator
dimming control circuit is the LED feed circuit and continuously supplies voltage to the 2 High, Auto 4WD, 4 Low and 4 High LEDs. When the
AWD mode has been selected by the driver, the transfer case shift control module (TCCM) provides a ground through the AWD indicator control
circuit illuminating the LED. The TCCM tests the AWD indicator circuit for unexpected voltage by monitoring the B+ supplied by the BCM on the
indicator dimming control circuit, by grounding the AWD indicator control circuit for 2 seconds during the bulb test at key ON.
Conditions for Running the DTC
B0770 01
* Ignition ON
* System voltage 10-18 V
* Instrument panel lights not dimmed.
* Daylight running lights MUST be commanded ON.
* Circuit tested when the AWD indicator is commanded OFF.
B0770 06
* Ignition ON
* System voltage 10-18 V
* Instrument panel lights not dimmed.
* Daylight running lights MUST be commanded ON.
* Circuit tested when the AWD indicator is commanded ON.
Conditions for Setting the DTC
B0770 01
The TCCM detects 3.4 V or greater on the AWD indicator control circuit when the AWD indicator is commanded ON.
B0770 06
The TCCM detects 1.6 V or less for 1.5 seconds on the AWD indicator control circuit when the AWD indicator is commanded OFF.
Action Taken When the DTC Sets
Normal operation, the SERVICE 4WD indicator is not commanded ON. Driver is informed of fault via bulb inspection.
Conditions for Clearing the DTC
* The TCCM clears the DTC once the condition for setting the DTC is no longer present.
* A history DTC clears after 40 consecutive warm up cycles without a fault present.
* History DTCs can be cleared using a scan tool.
Diagnostic Aids
* A TRUE B+ has enough current to light a test light.
