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 Descriptors
DTC B3420 02: AHLD Rear Axle Sensor Signal Circuit Short to GroundDTC 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Headlamp Leveling Module B+ | 1 | 1 | -- | -- |
Suspension Position Sensor - Front Voltage Reference | B3410 02, 2 | B3410 03, 2 | B3410 07, 2 | -- |
Suspension Position Sensor - Rear Voltage Reference | B3420 02, 3 | B3420 03, 3 | B3420 07, 3 | -- |
Suspension Position Sensor - Front Signal | B3410 02, 2 | B3410 03, 2 | B3410 07, 2 | -- |
Suspension Position Sensor - Rear Signal | B3420 02, 3 | B3420 03, 3 | B3420 07, 3 | -- |
Headlamp Leveling Motor (1) Control - Left | B2667 02 | B2667 05 | B2667 05 | -- |
Headlamp Leveling Motor (2) Control - Left | B2672 02 | B2672 05 | B2672 05 | -- |
Headlamp Leveling Motor (3) Control - Left | B1457 02 | B1457 05 | B1457 05 | -- |
Headlamp Leveling Motor (4) Control - Left | B1458 02 | B1458 05 | B1458 05 | -- |
Headlamp Leveling Motor (1) Control - Right | B2677 02 | B2677 05 | B2677 05 | -- |
Headlamp Leveling Motor (2) Control - Right | B2682 02 | B2682 05 | B2682 05 | -- |
Headlamp Leveling Motor (3) Control - Right | B1459 02 | B1459 05 | B1459 05 | -- |
Headlamp Leveling Motor (4) Control - Right | B1460 02 | B1460 05 | B1460 05 | -- |
Headlamp Leveling Motor - Left Low Reference | -- | 1 | -- | -- |
Headlamp Leveling Motor - Right Low Reference | -- | 1 | -- | -- |
Suspension Position Sensor - Front Low Reference | -- | 2 | -- | -- |
Suspension Position Sensor - Rear Low Reference | -- | 3 | -- | -- |
Headlamp Leveling Actuator - Left Ground | -- | 1 | -- | -- |
Headlamp Leveling Actuator - Right Ground | -- | 1 | -- | -- |
Headlamp Leveling Module Ground | -- | 1 | -- | -- |
1. Headlamp Leveling Malfunction 2. Suspension Position Sensor Malfunction - Front 3. Suspension Position Sensor Malfunction - Rear | ||||
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. |
| • | 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
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the LR suspension position sensor.
- Ignition OFF, verify that a test lamp illuminates between B+ and the low reference circuit terminal C.
- Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.
- Verify the scan tool Rear Leveling Position Sensor parameter is less than 0.5 volts.
- 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 all circuits test normal, test or replace the LR suspension position sensor.
| ⇒ | If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. |
| ⇒ | 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. |
| ⇒ | 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. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for headlamp leveling module replacement, setup, and programming |
