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 |
|---|---|---|---|---|
STOP/TRN Fuse B+ | 1 | 1 | 1 | -- |
Left Front Turn Signal Control | B3948 | B3948 | 1 | -- |
Right Front Turn Signal Control | B3949 | B3949 | 1 | -- |
Left Rear Stop/Turn Lamp Control | B3950 | B3950 | 1 | -- |
Right Rear Stop/Turn Lamp Control | B3951 | B3951 | 1 | -- |
Left Turn Signal Switch Signal | 1 | 1 | 1 | -- |
Right Turn Signal Switch Signal | 1 | 1 | 1 | -- |
Turn Signal/Multifunction Switch Ground | -- | 1 | -- | -- |
LF Park/Turn Signal Lamp Ground | -- | 1 | -- | -- |
RF Park/Turn Signal Lamp Ground | -- | 1 | -- | -- |
Left Tail/Stop and Turn Signal Lamp Ground | -- | 1 | -- | -- |
Right Tail/Stop and Turn Signal Lamp Ground | -- | 1 | -- | -- |
1. Park, License, and/or Tail Lamps Malfunction | ||||
Circuit/System Description
Ground is applied at all times at G200 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/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 turn signal switch signal circuit. The BCM then applies a pulsating voltage to the front and rear turn signal lamps through there respective voltage supply circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed ON and OFF.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, observe the scan tool Right and Left Turn Signal parameters while cycling the turn signal switch between the left and right positions. The readings should toggle between ON and OFF.
| ⇒ | If the readings do not change between the commanded states, refer to Turn Signal Switch Malfunction. |
| ⇒ | If the readings change between the commanded states and the IPC turn signal indicators are inoperative, refer to Turn Signal Indicators Malfunction. |
Circuit/System Testing
Turn Signal Switch Malfunction
- Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
- Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal G.
- Ignition ON, verify the scan tool Left Turn Signal parameter is OFF.
- Verify the scan tool Right Turn Signal parameter is OFF.
- Install a 3A fused jumper wire between the signal circuit terminal F and ground. Verify the scan tool Left Turn Signal parameter is ON.
- Install a 3A fused jumper wire between the signal circuit terminal H and ground. Verify the scan tool Right Turn Signal parameter is ON.
- If all circuits test normal, test or replace the turn signal/multifunction switch.
| ⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
| ⇒ | If not the specified value, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If not the specified value, test the signal circuit terminal H for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | 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 BCM. |
| ⇒ | 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 BCM. |
Turn Signal Lamps Malfunction
- Ignition OFF, disconnect the X1 harness connector at the BCM.
- Ignition ON, test for B+ between the B+ circuit terminal 46 and ground.
- Ignition OFF, reconnect the X1 harness connector at the BCM.
- Disconnect the harness connector at the inoperative turn signal lamp.
- Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground:
- Connect a test lamp between the appropriate control circuit terminal listed below and ground.
- Command the appropriate Turn Signal Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, replace the appropriate turn signal lamp assembly.
| ⇒ | If the less than the specified range, test the B+ circuit for a short to ground or an open/high resistance. |
| • | Left front turn signal ground terminal 3 |
| • | Right front turn signal ground terminal 3 |
| • | Left rear turn signal ground terminal B |
| • | Right rear turn signal ground terminal B |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| • | Left front turn signal control terminal 1 |
| • | Right front turn signal control terminal 1 |
| • | Left rear turn signal control terminal A |
| • | Right rear turn signal control terminal A |
| ⇒ | 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. |
Turn Signal Indicators Malfunction
Ignition ON, with a scan tool perform the Display Test for the instrument panel cluster (IPC) and observe the turn signal lamp indicators.
| ⇒ | If the turn signal lamp indicators illuminate during the test, replace the BCM. |
| ⇒ | If the turn signal lamp indicators do not illuminate during the test or remain illuminated at all times, replace the IPC. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM or IPC replacement, setup, and programming |
