MP 1625 / 1626-NQF Transfer Case

DTC B0775

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC B0775 01
- 4 High Indicator Circuit Short to Battery

DTC B0775 06
- 4 High Indicator Circuit Short to Ground or Open

Diagnostic Fault Information





Circuit/System Description

The 4 high indicator circuit consists of an indicator lamp feed circuit and an 4 high indicator lamp control circuit. When the 4 high mode has been selected, current is supplied to the 4 high indicator lamp by the interior lights dimming circuit, traveling through the 4 high indicator lamp LED, at which time the transfer case shift control module supplies the ground through the 4 high 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 high indicator control circuit.
* If the system detects a voltage of 2 volts or less for 1.5 seconds when the 4 high indicator is not commanded, the DTC is logged.
* If the system detects a voltage of 4.5 volts or more when the 4 high 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.

Diagnostic Aids

A short to ground on the 4 high indicator control circuit will cause the 4 high indicator to remain on at all times. An open or high resistance will cause the 4 high 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 high indicator is on at all times check the 4 high indicator control circuit for a short to ground. If the 4 high 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 high indicator off and on. If the 4 high indicator is still inoperative short to 4 high indicator control to ground, if the AWD indicator lights replace the module, program, and complete the motor learn procedure. If the 4 high indicator is still inoperative replace the switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Transfer Case Shift Control Switch Replacement (Without SLT) Transfer Case Shift Control Switch Replacement (With SLT)
* Control Module References for TCSCM replacement, setup, and programming
* Transfer Case High/Low Clutch Reset