DTC B3948-B3951
| DTC B3948-B3951 |
| 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 Descriptors |
DTC B3948 02
Left Front Turn Signal Circuit Short to Ground
DTC B3949 02
Right Front Turn Signal Circuit Short to Ground
DTC B3950 02
Left Rear Turn Signal Circuit Short to Ground
DTC B3951 02
Right Rear Turn Signal Circuit Short to Ground
| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
| Left Front Turn Signal Lamp Control | B3948 02 | 1 | 2 | - |
| Left Rear Turn Signal Lamp Supply Voltage | B3950 02 | 1 | 2 | - |
| Right Front Turn Signal Lamp Control | B3949 02 | 1 | 2 | - |
| Right Rear Turn Signal Lamp Supply Voltage | B3951 02 | 1 | 2 | - |
| Left Repeater Lamp Control | B3948 02 | 1 | 2 | - |
| Right Repeater Lamp Control | B3949 02 | 1 | 2 | - |
| Left Tail Lamp Ground | - | 1 | - | - |
| Right Tail Lamp Ground | - | 1 | - | - |
| 1. Turn Signal Lamps Inoperative 2. Turn Signal Lamps Always ON | ||||
| Circuit/System Description |
Ground is applied at all times to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the BCM through either the right turn or left turn signal switch signal circuit. The BCM then applies a pulsating voltage to the front and rear turn signal lamps through there respective voltage supply circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective turn signal indicator be pulsed ON and OFF.
| Conditions for Running the DTC |
When the appropriate turn signal is commanded
| Conditions for Setting the DTC |
B3948 02
The BCM detects a short to ground on the left front turn signal control circuit.B3949 02
The BCM detects a short to ground on the right front turn signal control circuit.B3950 02
The BCM detects a short to ground on the left rear turn signal control circuit.B3951 02
The BCM detects a short to ground on the right rear turn signal control circuit.| Action Taken When the DTC Sets |
The appropriate turn signal lamp is inoperative.
| Conditions for Clearing the DTC |
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The DTC will be current for as long as the fault is present.
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When the fault is no longer present, the DTC will be a history DTC.
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A history DTC will clear after 50 ignition cycles.
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| 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 scan tool information
| Circuit/System Verification |
| 1. |
Ignition ON, command the Left Front Turn Signal Lamp ON and OFF with a scan tool. The left front turn signal lamp should turn ON and OFF when changing between the commanded states.
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| 2. |
If the left front turn signal lamp is always ON or always OFF, refer to Front Turn Signal Lamp Malfunction.
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| 3. |
Command the Right Font Turn Signal Lamp ON and OFF with a scan tool. The right front turn signal lamp should turn ON and OFF when changing between the commanded states.
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| 4. |
If the right front turn signal lamp is always ON or always OFF, refer to Front Turn Signal Lamp Malfunction.
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| 5. |
Command the Left Rear Turn Signal Lamp ON and OFF with a scan tool. The left rear turn signal lamp should turn ON and OFF when changing between the commanded states.
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| 6. |
If the left rear turn signal lamp is always ON or always OFF, refer to Rear Turn Signal Lamp Malfunction.
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| 7. |
Command the Right Rear Turn Signal Lamp ON and OFF with a scan tool. The right rear turn signal lamp should turn ON and OFF when changing between the commanded states.
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| 8. |
If the right rear turn signal lamp is always ON or always OFF, refer to Rear Turn Signal Lamp Malfunction.
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| Circuit/System Testing |
Front Turn Signal Lamp Malfunction
| 1. |
Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.
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| 2. |
Test for less than 30 Ω between the ground circuit terminal listed below and ground.
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E4Y turn signal repeater lamp-left terminal 2
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E4Z turn signal repeater lamp-right terminal 2
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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. |
Disconnect the inline harness connector at the appropriate E4LF turn signal lamp-front listed below:
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E4LF turn signal lamp-left front X115 (Without TT6/TT7/TT8)
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E4LF turn signal lamp-left front X111 (With TT6/TT7/TT8)
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E4RF turn signal lamp-right front X116 (Without TT6/TT7/TT8)
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E4RF turn signal lamp-right front X112 (With TT6/TT7/TT8)
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| 5. |
Connect a test lamp between the control circuit terminal listed below and ground.
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E4LF turn signal lamp-left front terminal J
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E4RF turn signal lamp-right front terminal J
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E4Y turn signal repeater lamp-left terminal 1
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E4Z turn signal repeater lamp-right terminal 1
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| 6. |
Command the appropriate Turn Signal Lamp 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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| 7. |
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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| 8. |
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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| 9. |
If all circuits test normal, replace the turn signal lamp.
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Rear Turn Signal Lamp Malfunction
| 1. |
Ignition OFF, disconnect the X2 harness connector at the appropriate E4 turn signal lamp-rear.
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| 2. |
Test for less than 30 Ω between the ground circuit terminal 1 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 3 and ground.
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| 5. |
Command the appropriate Rear Turn Signal Lamp 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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| 6. |
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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| 7. |
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 the circuits test normal, replace the bulb or E4 turn signal lamp-rear.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Rear Turn Signal Lamp Bulb Replacement
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Front Turn Signal Lamp Bulb Replacement (TT6 Right Hand Bulb)
Front Turn Signal Lamp Bulb Replacement (TT6 Left Hand Bulb)
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Control Module References
for BCM replacement, setup, and programming
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