PRE-RELEASE
DTC B258A
| DTC B258A |
| 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 Descriptor |
DTC B258A 01
Low Beam Control Circuit Short to Battery
| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
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Low Beam Control
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1
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2
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B258A 01*
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-
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* Right/Left Headlamp Low Beam Always ON
1. Right/Left Headlamp Low Beam Always ON 2. Right/Left Headlamp Low Beam Always OFF |
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| Circuit/System Description |
The body control module (BCM) switches the headlamp low beams ON as soon it receives a signal from the headlamp switch or ambient light sensor. When this signal is received by the BCM, it applies a voltage trough the low beam relay and the low beam supply circuits which illuminates the low beams.
| Conditions for Running the DTC |
The headlamp switch in OFF, AUTO or LOW BEAM position.
| Conditions for Setting the DTC |
The BCM detects a short to battery on the control circuit.
| Action Taken When the DTC Sets |
Headlamp low beam malfunction.
| Conditions for Clearing the DTC |
The condition for setting the DTC is no 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
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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 Headlamp Low Beam Command test. The appropriate low beam lamp should be ON/OFF.
| Circuit/System Testing |
| 1. |
Ignition OFF, disconnect the KR49 Headlamp Low Beam Relay.
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| 2. |
Ignition ON, verify that a test lamp illuminates between the B+ circuit terminals listed below and ground:
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Terminal 30
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Terminal 86
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If the test lamp does not illuminate, test the B+ circuit for a short to ground or open/high resistance.
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| 3. |
Connect a test lamp between the control circuit of KR49 Headlamp Low Beam Relay terminal 85 and B+.
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| 4. |
Command the Headlamp Low Beam Command 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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| 5. |
If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
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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 Body Control Module.
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| 7. |
Remove the test lamp and reconnect the KR49 Headlamp Low Beam Relay
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| 8. |
Disconnect the harness of the appropriate headlamp and connect a test lamp between the control circuit terminal 3 and ground.
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| 9. |
Command the Headlamp Low Beam Command 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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| 10. |
If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the KR49 Headlamp Low Beam Relay.
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| 11. |
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 KR49 Headlamp Low Beam Relay.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Relay Replacement (Attached to Wire Harness)
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Control Module References
for information on BCM replacement, setup, and programming
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