To the top of the document
Volt
   
GMDE Start Page Load static TOC Load dynamic TOC Help?

DTC B3948 or B3949

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B3948 01: Left Front Indicator Circuit Short to Battery

DTC B3948 02: Left Front Indicator Circuit Short to Ground

DTC B3948 04: Left Front Indicator Circuit Open

DTC B3949 01: Right Front Indicator Circuit Short to Battery

DTC B3949 02: Right Front Indicator Circuit Short to Ground

DTC B3949 04: Right Front Indicator Circuit Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

F6DR Fuse B+

B3867 01, B3867 04, B3949 01, B3949 04

B3867 01, B3867 04, B3949 01, B3949 04

--

--

F8DR Fuse B+

B3948 01, B3948 04

B3948 01, B3948 04

--

--

Brake/Indicator Control - Left Rear

B3950 02

B3950 01, B3950 04

1

--

Brake/Indicator Control - Right Rear

B3951 02

B3951 01, B3951 04

1

--

Indicator Control - Left Front

B3948 02

B3948 01, B3948 04

1

--

Indicator Control - Right Front

B3949 02

B3949 01, B3949 04

1

--

Sidelight/Indicator Lamp Ground - Left Front

-

B2585 01, B2585 04, B3948 01, B3948 04

--

--

Sidelight/Indicator Lamp Ground - Right Front

-

B3867 01, B3867 04, B3949 01, B3949 04

--

--

Tail Lamp Ground - Left

--

1

--

--

Tail Lamp Ground - Right

--

1

--

--

1. Indicator Lamps and/or Indicators Malfunction

Circuit/System Description

Ground is applied at all times to the indicator/multifunction switch. The indicator lamps may only be activated with the vehicle ON/OFF switch in the SERVICE MODE or ON positions. When the indicator/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left indicator switch signal circuit. The BCM responds to the indicator switch input by applying a pulsating voltage to the front and rear indicator lamps through there respective control circuits. When a indicator request is received by the BCM, a serial data message is sent to the instrument panel cluster requesting the respective indicator indicator be pulsed ON and OFF.

Conditions for Running the DTC

Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

DTC B3948 01 and B3948 04

    • The BCM detects a short to ground or an open/high resistance in the F8DR fuse B+ circuit.
    • The BCM detects an open/high resistance in the left front indicator control circuit.
    • The BCM detects an open/high resistance in the left front indicator ground circuit.

DTC B3948 02

The BCM detects a short to ground in the left front indicator control circuit.

DTC B3949 01 and B3949 04

    • The BCM detects a short to ground or an open/high resistance in the F6DR fuse B+ circuit.
    • The BCM detects an open/high resistance in the right front indicator control circuit.
    • The BCM detects an open/high resistance in the right front indicator ground circuit.

DTC B3949 02

The BCM detects a short to ground in the right front indicator control circuit.

Action Taken When the DTC Sets

DTC B3948

    • The left front indicator is inoperative.
    • The left indicator indicator on the instrument panel cluster flashes rapidly.

DTC B3949

    • The right front indicator is inoperative.
    • The right indicator indicator on the instrument panel cluster flashes rapidly.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists.
    • A history DTC will clear once 100 consecutive malfunction free vehicle ON/OFF switch cycles have occurred.

Reference Information

Schematic Reference

    •  Exterior Lamps Schematics
    •  Body Control System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

DTC B3948

  1. Vehicle OFF, disconnect the X5 harness connector at the K9 Body Control Module.
  2. Vehicle in Service Mode, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
    3. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Vehicle OFF, connect the X5 harness connector at the K9 Body Control Module.
  4. Disconnect the harness connector at the E4N Sidelight/Indicator Lamp - Left front.
  5. Vehicle OFF, exterior lamps OFF, test for less than 5 Ω between the ground circuit terminal 1 and ground.
    6. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the control circuit terminal 3 and ground.
  7. Vehicle in Service Mode, command the Left Front Indicator Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    8. ⇒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.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K9 Body Control Module.
  8. If all circuits test normal, replace the E4N Sidelight/Indicator Lamp - Left front.

DTC B3949

  1. Vehicle OFF, disconnect the X2 harness connector at the K9 Body Control Module.
  2. Vehicle in Service Mode, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
    3. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Vehicle OFF, connect the X2 harness connector at the K9 Body Control Module.
  4. Disconnect the harness connector at the E4P Sidelight/Indicator Lamp - Right front.
  5. Vehicle OFF, exterior lamps OFF, test for less than 5 Ω between the ground circuit terminal 1 and ground.
    6. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the control circuit terminal 3 and ground.
  7. Vehicle in Service Mode, command the Right Front Indicator Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    8. ⇒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.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K9 Body Control Module.
  8. If all circuits test normal, replace the E4P Sidelight/Indicator Lamp - Right front.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Indicator Lamp Replacement : Volt → Ampera
    • Control Module References for BCM replacement, programming and setup
   


&#169© Copyright Chevrolet. All rights reserved