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 B3885 02: Trailer Left Tail Lamp Circuit Short to Ground
DTC B3885 04: Trailer Left Tail Lamp Circuit Open
DTC B3886 02: Trailer Right Tail Lamp Circuit Short to Ground
DTC B3886 04: Trailer Right Tail Lamp Circuit Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Trailer Left Tail Lamp | 3885 02 | 3885 04 | -- | --
Trailer Right Tail Lamp | B3886 02 | B3886 04 | -- | --

### Circuit/System Description

The headlamp switch is supplied with ground at all times. When the headlamp switch is placed in either the park or low beam position, ground is applied to the tail lamp signal circuit to the body control module (BCM). The BCM sends this message to the trailer lighting converter. The trailer lighting converter then applies a voltage to the appropriate trailer tail lamp through there respective voltage supply circuits.

### Conditions for Running the DTC

#### B3885 02, B3885 04, B3886 02 and B3886 04

The appropriate trailer tail lamp signal is active

### Conditions for Setting the DTC

#### B3885 02 or B3886 02

The trailer lighting converter detects a short to ground on the control circuit.

#### B3885 04 or B3886 04

The trailer lighting converter detects an open control circuit.

### Conditions for Clearing the DTC

The condition for setting the DTC is not longer present.

### Action Taken When the DTC Sets

The appropriate trailer tail lamp is inoperative.

### Reference Information

#### Schematic Reference

Trailer Connector/Provision 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 Verification

Ignition ON, perform the appropriate Trailer Tail Lamp test. The appropriate trailer tail lamp should be ON/OFF

### Circuit/System Testing

1. Ignition OFF, test for less than 5 Ω between the X88 Trailer Connector terminal 3, 11, 13 and ground.

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

2. Connect a test lamp between the appropriate X88 Trailer Connector terminal listed below and ground.

• | X88 Trailer Connector terminal 5

• | X88 Trailer Connector terminal 7

3. Command the appropriate Trailer Tail Lamp Active / Inactive test 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 signal circuit for a short to voltage. If the circuit tests normal, replace the K68 Trailer Lighting Converter.

⇒ | If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K68 Trailer Lighting Converter.

4. If all the circuits test normal, test the appropriate tail lamp circuit at the trailer.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for trailer lighting converter replacement, setup and programming