B3801

DTC B3801

Diagnostic Instructions

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

DTC Descriptor

DTC B3801
- Passenger Compartment Lamp Request Circuit

Circuit/System Description

The body control module (BCM) monitors the courtesy lamp switch signal circuit in order to determine when the courtesy/dome lamps should be illuminated. When the BCM senses that the courtesy lamp switch signal circuit is grounded when the switch is activated, the BCM will directly illuminate the courtesy/dome lamps.

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The BCM detects the courtest lamp switch is active while the IP lamp dimmer switch at the dim position.

Action Taken When the DTC Sets

The courtesy/dome lamps will be inoperative.

Conditions for Clearing the DTC

* This DTC will clear on current status after the condition for setting the fault is corrected.
* A history DTC will clear after 100 consecutive ignition cycles without a fault present.

Circuit/System Verification

1. Ignition ON, observe the scan tool dimming input parameter. The reading should be between 0.0 and 4,86 volts and change from low to high while the dimmer switch is rotated from bright to dim.

^ If the parameter is always high, refer to the dimmer switch circuit test.

2. Observe the scan tool courtesy lamp switch parameter. The reading should change between active and inactive when turning the switch on and off.

^ If the parameter is always active, refer to the courtesy lamp switch circuit test.

Circuit/System Testing

Dimmer Switch Circuit Test

1. Ignition OFF, disconnect the harness connector X1 at the headlamp switch.
2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit terminal H and ground.

^ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

3. Verify the scan tool dimming input parameter is less than 1.0 volt.

^ If greater than the specified range, test the signal circuit terminal G for a short to voltage. If the circuit tests normal, replace the BCM.

4. If all circuits test normal replace the headlamp switch.

Courtesy Lamp Switch Circuit Test

1. Ignition OFF, disconnect the harness connector X1 at the headlamp switch.
2. Ignition ON, verify the scan tool courtesy lamp switch parameter is inactive.

^ If not the specified value, test the signal circuit terminal J for a short to ground. If the circuit tests normal, replace the BCM.

3. If all circuits test normal replace the headlamp switch.

Repair Instructions

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

* Headlamp Switch Replacement