PRE-RELEASE
DTC B388B or B388C
| DTC B388B or B388C |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
has overviews of all diagnostic categories.
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| DTC Descriptors |
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 |
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Secondary Left Tail and Brake Lamp Control
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B388B 02
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B388B 04
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Secondary Right Tail and Brake Lamp Control
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B388C 02
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B388C 04
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| 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 |
B388B 02, B388B 04, B388C 02 and B388C 04
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.| Conditions for Clearing the DTC |
The condition for setting the DTC is not longer present.
| Action Taken When the DTC Sets |
The appropriate brake lamp/tail lamp is inoperative.
| 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
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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Scan Tool Reference
Control Module References for information on diagnostic tools
| 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:
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E42L Tail Lamp Assembly - Auxiliary Left
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E42R Tail Lamp Assembly - Auxiliary Right
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| 2. |
Test for less than 5 Ω between the appropriate ground circuit harness connector terminal listed below and ground:
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E42L Tail Lamp Assembly - Auxiliary Left harness connector terminal D
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E42R Tail Lamp Assembly - Auxiliary Right harness connector terminal D
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If greater than the specified value, test the appropriate ground circuit for an open circuit/high resistance.
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| 3. |
Connect a test lamp between the appropriate control circuit harness connector terminal listed below and ground:
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E42L Tail Lamp Assembly - Auxiliary Left harness connector terminal A
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E42R Tail Lamp Assembly - Auxiliary Right harness connector terminal A
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| 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.
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| 5. |
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.
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| 6. |
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.
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| 7. |
If all circuits test normal, test or replace the appropriate tail lamp.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Tail Lamp Replacement
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Control Module References
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