Circuit Description
Ground is applied to the turn signal switch. When the turn signal switch is placed in the turn left position, ground is applied to the body control module (BCM) through the left turn signal switch circuit. The BCM then applies a pulsating voltage to the LF and LR turn signal lamps through the LF and LR turn signal voltage supply circuits.
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.
Conditions for Setting the DTC
A short to ground or an open in the LF turn signal voltage supply circuit is present for longer then 0.1 second.
Action Taken When the DTC Sets
The left front turn signal lamp does not work.
Conditions for Clearing the DTC
| • | The DTC will clear on current status after the condition for setting the fault is corrected. |
| • | Will set a history code which will clear after 100 consecutive ignition cycles without a fault present. |
| • | History and current DTCs can be cleared using a scan tool. |
Diagnostic Aids
| • | 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 interment 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 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 |
Do the front left turn signal lamps flash on and off? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 5 |
4 | Test the LF turn signal voltage supply circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 8 |
5 | Test for continuity in the LF turn signal voltage supply circuit between the BCM harness connector C1 and the LF turn signal lamp. Refer to Circuit Testing . Is the continuity in the circuit? | Go to Step 9 | Go to Step 6 |
6 |
Did you find and correct the condition? | Go to Step 12 | Go to Step 7 |
7 | Test for continuity in the LF turn signal voltage supply circuit between the underhood electrical center and the LF turn signal lamp. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 8 |
8 | Inspect for a high resistance or an open at the harness connector of the underhood electrical center. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
9 | Inspect for a high resistance or an open at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 11 |
10 | Replace the underhood electrical center. Refer to Underhood Electrical Center or Junction Block Replacement . Did you complete the replacement? | Go to Step 12 | -- |
11 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 12 | -- |
12 |
Does the DTC reset? | Go to Step 2 | System OK |
