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B2725




DTC B2725

Diagnostic Instructions

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

DTC Descriptor
DTC B2725
- ATC Mode Switch Circuit Malfunction

Diagnostic Fault Information





Circuit/System Description

The active transfer case (ATC) mode switch circuit consists of 4 transfer case modes. The transfer case shift control module (TCCM) supplies a regulated 5 volts to the switch through the 5-volt reference circuit. The current is split, with part going through a common resistor and part going through a specific resistor of the currently depressed mode button - each mode has its own resistor. The current is then returned to the TCCM through the switch signal circuit.

The TCCM continuously monitors the switch signal circuit to determine whether a mode change has been requested by the driver.

The BW 4493/4494 transfer case has the following 4 modes:

* 4WD HI
* 4WD HI Locked
* 4WD LO Locked
* Neutral

Conditions for Running the DTC

* Ignition ON.
* System voltage 9-18 V.

Conditions for Setting the DTC

* The TCCM constantly monitors the voltage on the switch signal circuit.
* If the system detects a voltage level under 0.3 volt or greater than 0.5 volts for 600 seconds, the DTC is logged.

Action Taken When the DTC Sets

* All shifting disabled.
* The SERVICE 4WD indicator will remain illuminated for the remainder of the current ignition cycle.
* Front and rear locking differentials (if equipped) will maintain current state.

Conditions for Clearing the DTC

* The TCCM will clear the current DTC once the conditions for setting the DTC no longer exist.
* A history DTC will clear after 33 consecutive ignition cycles without a fault present.
* History DTCs can be cleared using a scan tool.

Diagnostic Aids

* EL-49741 - harness is a good source for 9 V.
* EL-49742 - harness is a good source for B+ and ground.

Reference Information
Schematic Reference

Transfer Case Control Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Transfer Case Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information.

Circuit/System Verification

1. Key ON, engine OFF.
2. Connect a scan tool.

Note: The transfer case shift control switch (TCSCS) is also known as the accessory or multifunction I/P switch.

3. Verify that all mode selections of the TCSCS match the following parameters in the Data Display feature of the scan tool:

* Mode Switch Selected
* Encoder Gear Position
* The corresponding Mode Indicator Light

Circuit/System Testing

1. Key OFF. Disconnect the X1 connector at the transfer case shift control switch (TCSCS). Install EL-49742 - harness. The TCSCS is also known as the accessory or multifunction I/P switch.

Note: When test probing harness terminals, it is imperative to use the proper test probe from the most current version of the J 35616 - Kit. Use of an improper test probe may deform the terminal, resulting in intermittent open conditions.

2. Key ON (Ignition C), engine OFF.
3. Using the L-BU probes J 35616-64B, test for 4.86-5.25 V between the 5-volt reference circuit, TCSCS X1 pin 16, and the ground terminal of EL-49742 - harness, black terminal.

• If the voltage is less than the specified value, test the 5-volt reference circuit for an open/high resistance or short to ground condition. If all circuits and connections test normal, test the TCCM for proper operation.
• If the voltage is greater than the specified value, test the 5-volt reference circuit for a short to voltage. If all circuits and connections test normal, test the TCCM for proper operation.

4. Using the L-BU probes J 35616-64B, test for 4.86-5.25 V between the 5-volt reference circuit, TCSCS X1 pin 16, and the switch signal circuit TCSCS X1 pin 15.

• If the voltage is less than the specified value, test the switch signal circuit for an open/high resistance, short to ground or short together. If all circuits and connections test normal, test the TCCM for proper operation.
• If the voltage is greater than the specified value, test the switch signal circuit for a short to voltage. If all circuits and connections test normal, test the TCCM for proper operation.

5. Using the L-BU probes J 35616-64B, test for greater than 100 ohm between the 5-volt reference circuit, TCSCS X1 pin 16, and all other pins of the TCSCS X1.

• If the resistance is less than the specified value, test the affected circuits for short together condition. If all circuits and connections test normal, test the TCCM for proper operation.

6. Using the L-BU probes J 35616-64B, test for greater than 100 ohm between the switch signal circuit TCSCS X1 pin 15, and all other pins of the TCSCS X1.

• If the resistance is less than the specified value, test the affected circuits for short together condition. If all circuits and connections test normal, test the TCCM for proper operation.

7. Test the TCSCS for proper operation.

Component Testing

TCSCS - Accessory / Multifunction I/P Switch
1. Key OFF. Remove the TCSCS.
2. Using the L-BU probes J 35616-65, measure the resistance for each of the mode positions of the TCSCS between the 5-volt reference circuit, TCSCS X1 pin 16, and the switch signal circuit TCSCS X1 pin 15.

• If the resistance is outside the specified ranges, replace the TCSCS.

3. Test the TCCM for proper operation.





TCCM - Mode Switch Circuit
1. Key ON, engine OFF. Install the TCSCS.
2. Using the Data Display feature of the scan tool, monitor the Mode Switch Return Voltage while pressing each of the TCSCS mode buttons.

• If the voltage is less than the specified value, test the affected circuit for an open/high resistance, short to ground or short together. If all circuits and connections test normal, replace the TCCM.
• If the voltage is greater than the specified value, test the affected circuit for a short to voltage. If all circuits and connections test normal, replace the TCCM.

3. Perform the Circuit/System Testing.





Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests)

* Transfer Case Shift Control Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for TCSCM replacement, setup, and programming

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