B3420

DTC B3420

Diagnostic Instructions

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



DTC Descriptors
DTC B3420 02
- AHLD Rear Axle Sensor Signal Circuit Short to Ground

DTC B3420 03
- AHLD Rear Axle Sensor Signal Circuit Voltage Below Threshold

DTC B3420 07
- AHLD Rear Axle Sensor Signal Circuit Voltage Above Threshold




Diagnostic Fault Information






Circuit Description

The rear suspension position sensor provides the headlamp level controller with rear suspension position information. The sensor is permanently grounded and has voltage supplied with the ignition in the ON or CRANK position. The sensor arm is connected to the control arm of the rear suspension. As the vehicle travels, the suspension compresses and rebounds moving the suspension position sensor arm. This causes the signal output of the sensor to change. The headlamp level controller compares this information with the front suspension position sensor information and adjusts the headlamp leveling as needed.


Conditions for Running the DTC

The headlamp leveling module performs this diagnostic test mode every 3.2 millisecond when the following conditions are met:

* The ignition is in the ON or CRANK position.
* The headlamps are ON.



Conditions for Setting the DTC

DTC B3420 will set when one of the following conditions occur:

B3420 02

The rear suspension position sensor voltage reference is less than 4.49 volts for 9.6 milliseconds.

B3420 03

The rear suspension position sensor voltage reference is less than 0.5 volt for 9.6 milliseconds.

B3420 07

The rear suspension position sensor voltage reference is 4.5 volts or greater for 9.6 milliseconds.


Actions Taken When the DTC Sets


B3420 02
* The headlamp level controller will turn OFF power to the rear suspension position sensor and wait 10 seconds before reapplying power to the sensor. If the reference voltage is less than 4.49 volts, the headlamp level controller will conclude a rear suspension position sensor failure has occurred.
* The headlamp level controller will disable the rear suspension position sensor.



B3420 03 and B3420 07
* If the headlamp leveling actuator has positioned the headlamps above the nominal level, the headlamp level controller will drive the headlamps to the nominal setting.
* If the headlamp leveling actuator has positioned the headlamps below the nominal level, the headlamp level controller will disable the headlamp leveling actuator and maintain the lower than nominal level.



Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* You issue a scan tool CLEAR DTCs command.
* A history DTC will clear once 40 consecutive malfunction free ignition cycles have occurred.



Diagnostic Aids

Important: When one of the suspension position sensor voltage reference or sensor signal circuits are shorted to ground, it may not possible to determine which suspension position sensor voltage reference or sensor signal circuits, front or rear, has failed. If this condition occurs, all suspension position sensor voltage reference and sensor signal circuits will have to be tested for a short to ground.




Reference Information
Schematic Reference

Headlight Leveling Schematics (Headlight Leveling Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems 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)


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the LR suspension position sensor.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the low reference circuit terminal C.

• If the test lamp does not illuminate, test the low reference circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.

• If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.


• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.

4. Verify the scan tool rear leveling position sensor parameter is less than 0.5 volts.

• If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the headlamp leveling module.

5. Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal A. Verify the scan tool rear leveling position sensor parameter is greater than 4.49 volts.

• If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp leveling module.

6. If all circuits test normal, test or replace the LR suspension position sensor.



Repair Instructions

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

* Headlamp Leveling Rear Suspension Height Sensor Replacement (Headlamp Leveling Rear Suspension Height Sensor Replacement)
* Control Module References (Programming and Relearning) for headlamp leveling module replacement, setup, and programming