Circuit Description
The mode switch circuit consists of 5 modes. The transfer case shift control module supplies a regulated 5 volts, DC to the switch through the 5-volt regulator circuit. The current travels through the resistor of the currently pressed mode button. The current is then returned to the transfer case shift control module through the switch signal circuit.
The transfer case shift control module constantly monitors this signal voltage to determine the condition of the mode switch circuit.
When each of the modes are selected they will complete a circuit through their own specific resistor while the button is pressed. The transfer case shift control module continuously monitors the switch input to determine whether the Neutral, Differential Lock, 4HI, 4HI Lock, or 4LO Lock mode was selected by the driver.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2725 ATC Mode Switch Circuit Malfunction
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The system voltage is 9-18 volts. |
Conditions for Setting the DTC
| • | The system constantly monitors the voltage on switch signal circuit. |
| • | If the system detects a voltage level under 0.3 volt or greater than 0.75 volts for 60 seconds, the DTC is logged. |
Action Taken When the DTC Sets
| • | All shifting will be disabled. |
| • | The SERVICE 4WD indicator will remain illuminated for the remainder of the current ignition cycle. |
Conditions for Clearing the DTC
| • | The transfer case shift control module will clear the current DTC if the condition for setting the DTC is not currently present. |
| • | A history DTC will clear after 33 consecutive ignition cycles without a fault present. |
| • | History DTCs can be cleared using a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests for proper operation of the transfer case mode select switch.
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This step tests the mode switch for proper resistance values in all mode switch states.
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This step tests for proper voltage on the 5-volt reference circuit.
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This step tests the 5-volt reference circuit for an open, high resistance, short to voltage, or short to ground.
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This step tests the switch signal circuit for an open, high resistance, short to voltage, or short to ground.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Transfer Case Control Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Does the scan tool indicate that the transfer case is in the mode that is selected? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | |
Does the DMM indicate all resistance values within the specified ranges? | Neutral 2,424-2,574 ohms 4 HI 3,553-3,773 ohms 4 HI Lock 1,817-1,930 ohms 4 LO Lock 5,256-5,581 ohms Differential Lock 747-793 ohms Normal 16,878-17,922 ohms | Go to Step 4 | Go to Step 7 | |
Check the voltage on the 5-volt reference circuit. Was the voltage within the specified range? | 4.8-5.1 V | Go to Step 6 | Go to Step 5 | |
Test the 5-volt reference circuit for an open, short to ground, short to voltage, or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 | |
Test the switch signal circuit for a short to voltage, short to ground, open, or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 | |
7 | Replace the mode switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | -- | Go to Step 9 | -- |
8 | Replace the transfer case shift control module. Refer to Control Module References for replacement, setup and programming. Did you complete the repair? | -- | Go to Step 9 | -- |
9 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
