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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B3420 AHLD Rear Axle Sensor Signal Circuit
DTC Symptom | DTC Symptom Descriptor |
|---|---|
02 | Short to Ground |
03 | Voltage Below Threshold |
07 | Voltage Above Threshold |
Conditions for Running the DTC
The headlamp level controller performs this diagnostic test mode every 3.2 milliseconds 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.
Action 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 scan tool CLEAR DTCs command is issued. |
| • | 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.
Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlight Leveling Schematics Connector End View Reference: Component Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Is DTC B3420 02 present? | -- | Go to Step 6 | Go to Step 3 |
3 | Is DTC B3420 03 present? | -- | Go to Step 4 | Go to Step 5 |
4 | Test the rear suspension position sensor voltage reference and sensor signal circuits for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 9 |
5 | Test the rear suspension position sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 9 |
6 |
Does the voltage measure less than the specified value? | 4.49 V | Go to Step 7 | Go to Step 8 |
7 | Locate and repair an open, high resistance, or short to ground in the rear suspension position sensor voltage reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
8 | Test the rear suspension position sensor low reference circuit for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 9 |
9 | Inspect for poor connections at the harness connector of the rear suspension position sensor . Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the headlamp level controller. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 |
11 |
Important: After replacing the suspension position sensor, perform the headlamp level controller setup procedure. Replace the rear suspension position sensor. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the scan tool display B3420 as current? | -- | Go to Step 13 | Go to Step 14 |
13 |
Important: After replacing the headlamp level controller, perform the setup procedure. Replace the headlamp level controller. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
