B1420

DTC B1420

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 B1420 02
- Device Voltage Short To Ground

Diagnostic Fault Information






Circuit/System Description

The liftgate control module controls operation of the liftgate latch motor and the liftgate actuator assembly. Under normal conditions the power latch can only be unlatched under power from the liftgate control module through an input from the liftgate handle switch, the driver door switch, or the remote keyless entry transmitter, but the liftgate may be manually closed to the primary latched position without the liftgate control module performing the power latch function. The ON/OFF switch in the driver door will enable or disable the power open/close operation of the actuator assembly but will have no effect on power latch operation. The drive motor is mated to a worm type gear off the actuator clutch and when the clutch is engaged the motor rotation is transferred to the clutch gear, intermediate gear, and actuator arm gear. The liftgate control module continuously monitors power liftgate operation and calculates its location and direction of travel using 2 inputs from the liftgate position sensor. One input returns the position of the liftgate relative to the latch along the x-axis and the other returns the position of the liftgate relative to the latch along the y-axis. The liftgate control module then uses these 2 inputs together to calculate its angle relative to the liftgate latch.

Conditions for Running the DTC

Battery voltage must be less than 9 volts or greater than 15.9 volts.

Conditions for Setting the DTC

* The supply voltage to the liftgate control module is less than 9V.
* The conditions above must be present for more than 5 seconds

Action Taken When the DTC Sets

The power liftgate will be inoperative.

Conditions for Clearing the DTC

* The DTC will be current for as long as the fault is present.
* When the fault is no longer present, the DTC will be a history DTC.
* A history DTC will clear after 50 ignition cycles.

Reference Information
Schematic Reference

Liftgate Schematics Liftgate Schematics
Connector End View Reference

Component Connector End Views Connector Views
Description and Operation

Liftgate Description and Operation Liftgate
Electrical Information Reference

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Circuit Testing Circuit Testing
* Wiring Repairs Wiring Repairs
* Connector Repairs Connector Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the X2 harness connector at the K39 Liftgate Control Module.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 4 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, replace the K39 Liftgate Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Liftgate Hydraulic Pump Replacement Liftgate Hydraulic Pump Replacement
* Control Module References Control Module References for liftgate module replacement, setup and programming