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 Descriptor
DTC B272B 03: Rear Differential Lock Mode Switch Circuit Below ThresholdDTC B272B 07: Rear Differential Lock Mode Switch Circuit Above Threshold
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Invalid |
|---|---|---|---|---|
Active Transfer Case Mode Switch Circuit | B272B 03 | B272B 03 | B272B 07 | -- |
Circuit/System Description
The mode switch circuit consists of 3 or 4 modes depending on how the vehicle is equipped with the transfer case shift control module only monitoring the rear differential lock portion of the switch. 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 if the Differential Lock mode was selected by the driver.
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 0.44 volt or greater than 0.56 volts for 60 seconds, the DTC is logged. |
Action Taken When the DTC Sets
| • | All differential lock requests will be ignored. |
| • | The SERVICE 4WD indicator will remain illuminated for the remainder of the current ignition cycle. |
| • | Failure Records will be stored. |
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 40 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
Description and Operation
Transfer Case Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information.
Circuit/System Testing
The 5 volt reference circuit and the switch signal will have to be checked for shorts to ground, opens, high resistance, and shorts to voltage by following the below listed steps.
- Reference the mode switch supply voltage with a scan tool.
- If the rear differential lock switch return does not read 4.8-5.2 volts check the rear differential lock switch signal circuit and the 5 volt reference circuits for a short to ground, short to voltage, open, or high resistance.
| ⇒ | The scan tool should indicate 4.8-5.2 volts. If the scan tool indicates the voltage is within this specification then with a jumper wire short the switch signal circuit pin C1 pin 1 on the switch to the 5 volt reference circuit C1 pin 9 on the switch. If the rear differential lock switch return voltage on the scan tool measures 4.8-5.2 volts then replace the switch. |
| ⇒ | If no shorts or high resistance are found on the switch signal or 5 volt reference circuits then replace the transfer case shift control module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for TCSCM replacement, setup, and programming |
Repair Verification
Clear the DTCs and operate the vehicle so that the DTC runs, if the DTC runs and passes then the repair was successful.
