Circuit Description
When the turn signal switch is placed in the left turn position, the body control module (BCM) cycles positive voltage ON and OFF to the LF turn signal lamp through the left front turn signal lamp supply voltage circuit. The front turn signal lamps illuminate steady for daytime running lamp (DRL) operation.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B3948 Left Front Turn Signal Circuit
Conditions for Running the DTC
| • | The battery voltage must be between 9-16 volts. |
| • | Ignition switch in the RUN position. |
| • | Turn signal switch placed in the left turn position. |
Conditions for Setting the DTC
| • | An open in the left front turn signal lamp supply voltage circuit is present for longer than 0.1 second. |
| • | An open LF turn signal bulb |
| • | An open in the ground circuit of the lamp |
| • | An open or short to ground in the battery positive voltage circuit from the STOP/TURN 20 amp fuse in the instrument panel (I/P) fuse block |
Action Taken When the DTC Sets
The left front turn signal lamp and DRL does not work.
Conditions for Clearing the DTC
| • | The DTC will clear on current status after the condition for setting the fault is corrected. |
| • | A history code will clear after 100 consecutive ignition cycles without a fault present. |
| • | History and current DTCs can be cleared using a scan tool. |
Diagnostic Aids
| • | An open or short to ground in the battery positive voltage circuit of the STOP/TURN 20 amp use will cause all 4 turn signal DTCs. |
| • | Check the LF turn lamp bulb. If the bulb is open, DTC B3948 will be set. |
| • | If the DTC is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections . |
| • | An intermittent short to ground or an open in the following locations may cause an intermittent malfunction to occur: |
| - | The BCM |
| - | The underhood electrical center |
| - | The left front turn signal lamp supply voltage circuit |
Step | Action | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List | |||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||
2 |
Does the LF turn signal lamp flash ON and OFF? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||||
3 |
Is the bulb OK? | Go to Step 4 | Go to Step 8 | ||||||||
4 | Test the ground circuit of the inoperative lamp for high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 5 | ||||||||
5 | Test the left front turn signal supply voltage circuit for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 7 | ||||||||
6 | Test the battery positive voltage circuit from the STOP/TURN 20 amp fuse for a short to ground or an open. Did you find and correct the condition? | Go to Step 10 | Go to Step 7 | ||||||||
7 | Inspect for a high resistance or an open at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 9 | ||||||||
8 | Replace the bulb. Refer to Park/Turn Signal Lamp Bulb Replacement . Did you complete the replacement? | Go to Step 10 | -- | ||||||||
9 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 10 | -- | ||||||||
10 |
Does the DTC reset? | Go to Step 3 | System OK | ||||||||
