Circuit Description
The body control module (BCM) controls the left front turn signal, hazard lamp, and daytime running lamp (DRL). The BCM supplies voltage to control the lighting functions. The BCM monitors the left turn signal lamp supply voltage circuit for proper operation.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B3948 Left Front Turn Signal Circuit
Conditions for Setting the DTC
B3948 02
Will set if there is a short to ground in the left front turn signal circuit
B3948 05
Will set if there is an open or short to voltage in the left front turn signal circuit
Action Taken When the DTC Sets
| • | The Service Vehicle Soon message will be displayed. |
| • | Stores a DTC B3948 in the BCM memory |
| • | If the failure is an open, short to ground, or to power, the rear turn signal flashes at double rate. |
Conditions for Clearing the DTC
| • | This DTC requires an ignition cycle in order to change from current to history. |
| • | The BCM no longer detects continuous battery voltage on the LH turn signal monitor circuit for longer than 5 seconds. |
| • | A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Diagnostic Aids
| • | The following conditions may cause an intermittent malfunction: |
| - | There is an intermittent short to voltage in the LH turn signal monitor circuit. |
| - | The turn signal switch or the hazard switch is shorted internally or is sticking. |
| • | If the BCM detects continuous voltage on the LH turn signal monitor circuit, the BCM interprets this as a short to voltage. The BCM will continue with normal DRL operation, and the LF turn signal will remain inoperative. |
| • | If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Refer to Testing for Intermittent Conditions and Poor Connections . |
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Exterior Lights Schematics | |||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||
2 |
Does the left front turn signal operate properly? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||
3 | Observe the left front turn signal lamp. Is the lamp always ON? | Go to Step 6 | Go to Step 4 | ||||||
4 | Inspect the condition of the left front turn signal bulb. Is the bulb burned out? | Go to Step 8 | Go to Step 5 | ||||||
5 | Test for the following in the left turn signal lamp supply voltage circuit:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 7 | ||||||
6 | Test for a short to voltage in the left turn signal lamp supply voltage circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 7 | ||||||
7 | Inspect for poor connections 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 left front turn signal bulb. Refer to Headlamp Capsule 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 2 | System OK | ||||||
