GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Monte Carlo 🢒 Body Systems 🢒 Lighting 🢒 Turn Signal 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

B+, BCM C4 terminal 1

2

2

--

--

B+, BCM C4 terminal 2

B2615 00, 5

B2615 00, 5

--

--

B+, BCM C4 terminal 3

7

7

--

--

Left Front Turn Signal Lamp Supply Voltage

4

4

4

--

Right Front Turn Signal Lamp Supply Voltage

5

5

5

--

Left Rear Stop/Turn Lamp Supply Voltage

6

6

6

--

Right Rear Stop/Turn Lamp Supply Voltage

7

7

7

--

Left Turn Signal Switch Signal

2

2

2

--

Right Turn Signal Switch Signal

3

3

3

--

Ground - Turn Signal/Multifunction Switch

--

1

--

--

Ground - LF Park/Turn Signal Lamp

--

4

--

--

Ground - RF Park/Turn Signal Lamp

--

5

--

--

Ground - Left Tail/Stop and Turn Signal Lamp

--

6

--

--

Ground - Right Tail/Stop and Turn Signal Lamp

--

7

--

--

1. All turn signals inoperative

2. Left turn signals malfunction

3. Right turn signals malfunction

4. Left front turn signal malfunction

5. Right front turn signal malfunction

6. Left rear stop/turn signal malfunction

7. Right rear stop/turn signal malfunction

Circuit/System Description

The BCM controls the vehicle turn signals based on inputs from the turn signal/multifunction switch. With the turn signal/multifunction switch in the left turn position, a ground path is provided on the left turn signal switch signal circuit, indicating a left turn signal request. With the turn signal/multifunction switch in the right turn position, a ground path is provided on the right turn signal switch signal circuit, indicating a right turn signal request. When the specific request is seen, the BCM will pulse the respective turn signal lamp supply voltage circuits, illuminating the turn signal lamps.

When a turn signal request is seen by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems 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

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification
  1. Ignition ON, observe the scan tool Left Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the left turn signal ON and OFF. The reading should change between Active and Inactive.
    2. ⇒If the reading does change between the specified values, refer to Turn Signal/Multifunction Switch Circuit Test.
  2. View the scan tool Right Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the right turn signal ON and OFF. The reading should change between Active and Inactive.
    3. ⇒ If the reading does change between the specified values, refer to Turn Signal/Multifunction Switch Circuit Test.
  3. Command the turn signals listed below ON and OFF with a scan tool. The respective turn signal should turn ON and OFF when changing between the commanded states.
    4. • LF Turn Signal
    • RF Turn Signal
    • LR Turn Signal
    • RR Turn Signal
    ⇒If the turn signal does not turn ON and OFF as specified, refer to Turn Signal Circuit Test.
  4. With the turn signal/multifunction switch in the left turn position, verify the left turn signal indicator is illuminated on the IPC.
    5. ⇒If the turn signal indicator is not illuminated, refer to Turn Signal Indicators Malfunction.
  5. With the turn signal/multifunction switch in the right turn position, verify the right turn signal indicator is illuminated on the IPC.
    6. ⇒If the turn signal indicator is not illuminated, refer to Turn Signal Indicators Malfunction.

Circuit/System Testing

Turn Signal/Multifunction Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector C1 at the turn signal/multifunction switch.
  2. Verify that a test lamp illuminates between the ground circuit terminal E and B+.
    3. ⇒If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Left Turn Signal Switch parameter is Inactive.
    4. ⇒If not the specified value, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM.
  4. Verify the scan tool Right Turn Signal Switch parameter is Inactive.
    5. ⇒If not the specified value, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal D and the ground circuit terminal E. Verify the scan tool Left Turn Signal Switch parameter is Active.
    6. ⇒If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal F and the ground circuit terminal E. Verify the scan tool Right Turn Signal Switch parameter is Active.
    7. ⇒If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
  7. If all circuits test normal, test or replace the turn signal/multifunction switch.

Turn Signal Circuit Test

  1. Ignition OFF, disconnect the harness connect C4 at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the B+ circuits listed below and ground.
    3. • B+ terminal 1
    • B+ terminal 2
    • B+ terminal 3
    ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and circuit fuse is open, test the appropriate control circuit(s) listed below for a short to ground.
    • LT T/SIG Fuse - terminal 1 X5 and terminal 4 X5
    • RT T/SIG Fuse - terminal 2 X5
    • INT LIGHTS Fuse - terminal 5 X4
  3. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
  4. Verify that a test lamp illuminates between the ground circuit terminal G and B+.
    5. ⇒If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  5. Connect a test lamp between the control circuit terminal A and the ground circuit terminal G.
  6. Ignition ON, command the appropriate turn signal ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    7. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒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 BCM.
  7. If all circuits test normal, test or replace the affected turn signal lamp.

Component Testing

Turn Signal/Multifunction Switch

  1. Ignition OFF, disconnect the C1 harness connector at the turn signal/multifunction switch.
  2. Test for infinite resistance between the terminals listed below and the ground circuit terminal E with the switch in the neutral position.
    3. • Signal terminal D
    • Signal terminal F
    ⇒If not the specified value, replace the turn signal/multifunction switch.

    Important: If the switch tests open in any switch position other than Off, test the switch signal circuits for a short to voltage before replacing the switch.

  3. Test for less than 2.0 ohms between the signal circuit terminal D and the ground circuit terminal E with the switch in the left turn position.
    4. ⇒If greater than the specified range, replace the turn signal/multifunction switch.
  4. Test for less than 2.0 ohms between the signal circuit terminal F and the ground circuit terminal E with the switch in the left turn position.
    5. ⇒If greater than the specified range, replace the turn signal/multifunction switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Turn Signal Multifunction Switch Replacement
    •  Headlamp Bulb Replacement
    •  Rear Turn Signal Lamp Bulb Replacement
    •  Control Module References for BCM and IPC replacement, setup, and programming