PRE-RELEASE
DTC B2657
| DTC B2657 |
| 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
provides an overview of each diagnostic category.
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| DTC Descriptor |
DTC B2657 02
Ignition Switch Halo Lamp Circuit Short to Ground
| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
| Ignition Switch Halo Lamp Control | B2657 02 | 2 | 1 | - |
| Ignition Switch Halo Lamp Ground | - | 2 | - | - |
| 1. Ignition Switch Halo Lamp Always ON 2. Ignition Switch Halo Lamp Always OFF | ||||
| Circuit/System Description |
The body control module (BCM) supplies a voltage reference through the backlight dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the backlight dimmer switch to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the backlight lamp control circuit. This will illuminate the ignition mode switch halo lamp.
| Conditions for Running the DTC |
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The ignition is ON.
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The headlamps or park lamps are ON.
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| Conditions for Setting the DTC |
The BCM detects a short to ground on the ignition switch halo lamp control circuit.
| Action Taken When the DTC Sets |
The BCM will not illuminate the ignition switch halo lamp.
| Conditions for Clearing the DTC |
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The condition responsible for setting the DTC no longer exists.
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A history DTC will clear once 100 consecutive malfunction ignition cycles have occurred.
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| Reference Information |
Schematic Reference
Interior Lights Dimming Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Interior 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 scan tool information
| Circuit/System Verification |
Ignition ON, command the LED Backlighting ON and OFF with a scan tool. The ignition switch halo lamp should turn ON and OFF when changing between the commanded states.
| Circuit/System Testing |
| 1. |
Ignition OFF, disconnect the harness connector at the S38 ignition mode switch.
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| 2. |
Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 Ω between the ground circuit terminal 4 and ground.
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| 3. |
If greater than the specified range, test the ground circuit for an open/high resistance.
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| 4. |
Connect a test lamp between the control circuit terminal 8 and the ground circuit terminal 4.
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Command the LED Backlighting ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
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If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
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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 K9 BCM.
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| 8. |
If all circuits test normal, test or replace the S38 ignition mode switch.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Ignition and Start Switch Replacement
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Control Module References
for BCM replacement, programming and setup
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