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DTC B3420

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 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

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

AHLD Rear Axle Sensor Signal Circuit

B3420 02

B3420 03

B3420 07

-

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 levelling as needed.

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

B3420 02

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

B3420 03

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

B3420 07

The rear suspension position sensor voltage reference is 4.5 V 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 V, 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 levelling actuator has positioned the headlamps above the nominal level, the headlamp level controller will drive the headlamps to the nominal setting.
    • If the headlamp levelling actuator has positioned the headlamps below the nominal level, the headlamp level controller will disable the headlamp levelling 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

Note: 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 .

Reference Information

Schematic Reference

Headlamps/Daytime Running Lamps (DRL) Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Step

Action

Values

Yes

No

Schematic Reference:Headlamps/Daytime Running Lamps (DRL) Schematics

Connector End View Reference: Component Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

-

Go to Step 2

Go to Diagnostic System Check - Vehicle

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

  1. Turn OFF the ignition.
  2. Disconnect the rear suspension position sensor wiring harness plug.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage of the voltage reference circuit at the rear suspension position sensor wiring harness plug.

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 wiring harness plug 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 wiring harness plug 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

  1. Turn ON the ignition, with the engine OFF.
  2. Use the scan tool in order to clear the DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC.

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

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

-

Go to Step 2

System OK

   


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