For 1990-2009 cars

### 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 Descriptor

DTC B3871 00: Rear Side Markers Circuit Malfunction

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Park Lamp Switch Signal | 2 | B2662 05 | B2662 05 | --
License Lamp Control | B3883 00 | B3883 00 | 1 | --
Park Lamp - RF Control | B3867 00 | B3867 00 | 1 | --
Park Lamp - LF Control | B2585 00 | B2585 00 | 1 | --
Marker Lamp - LF Control | 1 | 1 | 1 | --
Marker Lamp - RF Control | 1 | 1 | 1 | --
Marker Lamp Rear Control | B3871 00 | B3871 00 | 1 | --
License Lamp Ground | -- | 1 | -- | --
Headlamp Switch Ground | -- | 2 | -- | --
Marker Lamp - LF Ground | -- | 1 | -- | --
Marker Lamp - RF Ground | -- | 1 | -- | --
Marker Lamp - LR Ground | -- | 1 | -- | --
Marker Lamp - RR Ground | -- | 1 | -- | --
Park Lamps - LF Ground | -- | 1 | -- | --
Park Lamps - RF Ground | -- | 1 | -- | --
Tail/Stop and Turn Signal Lamps - LR Ground | -- | 1 | -- | --
Tail/Stop and Turn Signal Lamps - RR Ground | -- | 1 | -- | --
1. Park, License, and/or Tail Lamps Malfunction 2. Park Lamp Switch Malfunction

### Circuit/System Description

The headlamp switch is supplied with voltage from the instrument panel cluster (IPC) by two signal circuits, the AUTO lamps signal circuit and the PARK lamp signal circuit. When the headlamp switch is placed in the PARK position, the park lamp signal circuit is provided with ground through the switch contacts of the park lamp switch to a common headlamp switch ground back to the IPC. The IPC interprets the flow of voltage and responds by sending a serial data message to the underhood electrical center (UEC) and the rear electrical center (REC) requesting the front and rear park lamps be activated. The UEC and REC respond by applying voltage to there respective park, marker, and license lamp control circuits illuminating the park, marker and license lamps.

### Conditions for Running the DTC

• | Battery voltage must be between 9-16 volts.

• | Park lamps ON.

### Conditions for Setting the DTC

The DTC will set when the REC detects a short to ground or an open/high resistance in the rear side marker lamps control circuit.

### Actions Taken When the DTC Sets

When DTC B3871 00 is present, the rear side marker lamps control circuit will be disabled.

### Conditions for Clearing the DTC

• | The condition responsible for setting the DTC no longer exists.

• | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Exterior Lighting Systems Description and Operation

#### 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

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the inoperative side marker lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 2 and ground.
4. Command the Rear Side Markers Test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the REC.

⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the REC.

5. If all circuits test normal, replace the inoperative side marker lamp.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Rear Side Marker Lamp Replacement

• | Control Module References for REC replacement, setup, and programming