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Indicator Lamps and/or Indicators Malfunction

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.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Left Front Indicator Lamp Control

B3948 02

B3948 04

B3948 01

--

Right Front Indicator Lamp Control

B3949 02

B3949 04

B3949 01

--

Left Rear Indicator Lamp Control

B3950 02

B3950 04

B3950 01

-

Right Rear Indicator Lamp Control

B3951 02

B3951 04

B3951 01

-

Left Repeater Lamp Control

B3948 02

8

B3948 01

-

Right Repeater Lamp Control

B3949 02

9

B3949 01

-

Left Indicator Switch Signal

2

2

2

--

Right Indicator Switch Signal

3

3

3

--

Left Tail Lamp Ground

-

6

--

--

Left Repeater Lamp Ground

-

8

--

--

Right Repeater Lamp Ground

-

9

--

--

Right Tail Lamp Ground

-

7

--

--

Indicator/Multifunction Switch Ground

--

1

--

--

Left Front Indicator Lamp Ground

--

4

--

--

Right Front Indicator Lamp Ground

-

5

--

--

1. All Indicators Lamps and/or Indicators Inoperative

2. Left Indicators Malfunction

3. Right Indicators Malfunction

4. Left Front Indicator Malfunction

5. Right Front Indicator Malfunction

6. Left Rear Indicator Malfunction

7. Right Rear Indicator Malfunction

8. Left Repeater Lamp Malfunction

9. Right Repeater Lamp Malfunction

Circuit/System Description

Ground is applied at all times to the indicator/multifunction switch. The indicator lamps may only be activated with the ignition switch in the ON or START position. 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 then applies a pulsating voltage to the front and rear indicator lamps through there respective voltage supply circuits. When a indicator request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective indicator indicator be pulsed ON and OFF.

Reference Information

Schematic Reference

Exterior Lamps 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 Verification

Ignition ON, observe the scan tool Right Turn Signal Switch parameter and Left Turn Signal Switch parameter while switching the S78 Turn Signal/Multifunction Switch between the left and right positions. The readings should toggle between Active and Inactive.

If the readings do not change between the commanded states, refer to Indicator Switch Malfunction.
If the readings change between the commanded states and the instrument cluster indicator indicators are inoperative, refer to Indicator Indicators Malfunction.

Circuit/System Testing

Indicator Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the S78 Indicator/Multifunction Switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 3.
  3. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Left Turn Signal Switch parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
  6. Verify the scan tool Right Turn Signal Switch parameter is Inactive.
  7. If not the specified value, test the signal circuit terminal 7 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
  8. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground. Verify the scan tool Left Turn Signal Switch parameter is Active.
  9. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  10. Install a 3 A fused jumper wire between the signal circuit terminal 7 and ground. Verify the scan tool Right Turn Signal Switch parameter is Active.
  11. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  12. If all circuits test normal, test or replace the S78 Indicator/Multifunction Switch.

Indicator Lamps Malfunction

  1. Ignition OFF, disconnect the harness connector at the inoperative indicator lamp.
  2. Disconnect the negative terminal of the C1 Battery.
  3. Ignition OFF, exterior lamps OFF, test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
  4. • E4LF Turn Signal Lamp - Left Front ground circuit terminal 1
    • E4RF Turn Signal Lamp - Right Front ground circuit terminal 1
    • E4LR Indicator Lamp - Left Rear ground circuit terminal 3
    • E4RR Indicator Lamp - Right Rear ground circuit terminal 3
    • E4Y Indicator Repeater Lamp - Left ground circuit terminal 1
    • E4Z Indicator Repeater Lamp - Right ground circuit terminal 1
    If greater than the specified range, test the ground circuit for an open/high resistance.
  5. Reconnect the negative terminal to the C1 Battery.
  6. Connect a test lamp between the appropriate control circuit terminal listed below and ground.
  7. • E4LF Turn Signal Lamp - Left Front control circuit terminal 2
    • E4RF Turn Signal Lamp - Right Front control circuit terminal 2
    • E4LR Indicator Lamp - Left Rear control circuit terminal 2
    • E4RR Indicator Lamp - Right Rear control circuit terminal 2
    • E4Y Indicator Repeater Lamp - Left ground circuit terminal 2
    • E4Z Indicator Repeater Lamp - Right ground circuit terminal 2
  8. Command with the appropriate Indicator Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  9. 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 circuit tests normal, replace the K9 Body Control Module.
  10. If all circuits test normal, replace the appropriate indicator lamp assembly.

Indicator Indicators Malfunction

Ignition ON, command the All Indicators test ON and OFF with the scan tool, verify both indicator indicators changes between turn ON and OFF.

If both indicator indicators change between illuminate and not illuminate during the test, replace the K9 Body Control Module.
If one or both indicator indicators do not illuminate during the test or remain illuminated at all times, replace the P16 Instrument Cluster.

Component Testing

Indicator Switch

  1. Ignition OFF, disconnect the harness connector at the S78 Indicator/Multifunction Switch.
  2. Remove S78 Turn Signal/Multifunction Switch.
  3. Test for greater than 500 kΩ between signal terminal 1 and ground terminal 3.
  4. If less than the specified value, replace the S78 Indicator/Multifunction Switch.
  5. Test for greater than 500 kΩ between signal terminal 7 and ground terminal 3.
  6. If less than the specified value, replace the S78 Indicator/Multifunction Switch.
  7. Push the S78 Turn Signal/Multifunction Switch turn left. Test for less than 5 Ω between signal terminal 1 and ground terminal 3.
  8. If greater than the specified value, replace the S78 Indicator/Multifunction Switch.
  9. Push the S78 Turn Signal/Multifunction Switch turn right. Test for less than 5 Ω between signal terminal 7 and ground terminal 3.
  10. If greater than the specified value, replace the S78 Indicator/Multifunction Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Headlamp Replacement
    •  Front Side Indicator Lamp Replacement
    •  Tail Lamp Replacement
    • Control Module References for BCM or instrument cluster replacement, setup, and programming
   


© Copyright Chevrolet. All rights reserved
   


© Copyright Chevrolet. All rights reserved