DTC B388B or B388C
Diagnostic Instructions
DTC Descriptor
| DTC B388B 02: Secondary Left Tail and Brake
Lamp Circuit Short to Ground |
| DTC B388B 04: Secondary Left Tail and Brake
Lamp Circuit Open |
| DTC B388C 02: Secondary Right Tail and Brake
Lamp Circuit Short to Ground |
| DTC B388C 04: Secondary Right Tail and Brake
Lamp Circuit Open |
Diagnostic Fault Information
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Signal Performance
|
Secondary Left Tail and Brake Lamp Control
|
B388B 02
|
B388B 04
|
-
|
-
|
Secondary Right Tail and Brake Lamp Control
|
B388C 02
|
B388C 04
|
-
|
-
|
|
| |
Circuit/System Description
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 brake pedal position sensor
provides an analog voltage signal to the BCM. The BCM sends this
messages to the trailer lighting converter. The trailer lighting
converter responds by applying battery voltage to the left tail
lamp and to the right tail lamp control circuits. This energizes
the tail lamps.
Conditions for Running the DTC
The appropriate brake lamp/tail lamp signal is active.
Conditions for Setting the DTC
B388B 02 or B388C 02
The control module detects a short to ground on the control
circuit.
B388B 04 or B388C 04
The control module detects an open control circuit.
Action Taken When the DTC Sets
The appropriate brake lamp/tail lamp is inoperative.
Conditions for Clearing the DTC
The condition for setting the DTC is not longer present.
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
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, perform the appropriate Auxiliary Tail and Brake
Lamp test. The appropriate tail and brake lamps should be
ON/OFF.
Circuit/System Testing
| 1. |
Ignition OFF, disconnect the
appropriate harness connector at the tail lamp listed below:
|
| |
• |
E42L Tail Lamp Assembly -
Auxiliary Left |
| |
• |
E42R Tail Lamp Assembly -
Auxiliary Right |
| 2. |
Test for less than 5 Ω
between the appropriate ground circuit harness connector terminal
listed below and ground: |
| |
• |
E42L Tail Lamp Assembly -
Auxiliary Left terminal D |
| |
• |
E42R Tail Lamp Assembly -
Auxiliary Right terminal A |
| ⇒ |
If greater than the specified value, test the
appropriate ground circuit for an open/high resistance. |
| 3. |
Connect a test lamp between
the appropriate control circuit harness connector terminal listed
below and ground: |
| |
• |
E42L Tail Lamp Assembly -
Auxiliary Left terminal B |
| |
• |
E42R Tail Lamp Assembly -
Auxiliary Right terminal C |
| 4. |
Command the appropriate
Auxiliary Tail and Brake Lamp 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
appropriate control circuit for a short to voltage. If the circuit
tests normal, replace the K68 Trailer Lighting Control Module. |
| ⇒ |
If the test lamp is always OFF, test the
appropriate control circuit for a short to ground or an open/high
resistance. If the circuit tests normal, replace the K68 Trailer
Lighting Control Module. |
| 5. |
If all circuits test normal,
test or replace the appropriate tail lamp. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
|
