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 |
|---|---|---|---|---|
LT Stop TRN Fuse B+ Supply | 1 | 1 | -- | -- |
RT Stop TRN Fuse B+ Supply | 1 | 1 | -- | -- |
Hazard Switch Signal | 2 | 2 | 2 | -- |
Turn Signal Switch Signal -- Left | 3 | 3 | 3 | -- |
Turn Signal Switch Signal -- Right | 3 | 3 | 3 | -- |
Turn Signal Lamp Control -- LF | 1 | 1 | 1 | -- |
Turn Lamp Control -- LR | 1 | 1 | 1 | -- |
Turn Signal Lamp Control -- RF | 1 | 1 | 1 | -- |
Turn Lamp Control -- RR | 1 | 1 | 1 | -- |
Hazard Switch Ground | -- | 2 | -- | -- |
Lower Stop/Turn Lamp Ground -- RR | -- | 1 | -- | -- |
Lower Stop/Turn Lamp Ground -- LR | -- | 1 | -- | -- |
Park/Turn Signal Lamp -- LF | -- | 1 | -- | -- |
Park/Turn Signal Lamp -- RF | -- | 1 | -- | -- |
Repeater Lamp Ground -- RF | -- | 1 | -- | -- |
Repeater Lamp Ground -- LF | -- | 1 | -- | -- |
Turn Signal/Multifunction Switch Ground | -- | 3 | -- | -- |
Turn Signal Lamp - LF Ground | -- | 1 | -- | -- |
Turn Signal Lamp - RF Ground | -- | 1 | -- | -- |
Upper Stop/Turn Lamp Ground -- LR | -- | 1 | -- | -- |
Upper Stop/Turn Lamp Ground -- RR | -- | 1 | -- | -- |
1. Turn Signal Lamps and/or Indicators Malfunction 2. Hazard Lamps Malfunction 3. Turn Signal Switch Malfunction | ||||
Circuit/System Description
When the turn signal switch is placed in either the left or right position, a ground signal is completed from the turn signal switch to the BCM. When the hazard flasher switch is activated, a ground signal is completed from the turn signal/hazard switch to the BCM. The BCM then sends a pulsating voltage signal through the fuses to the appropriate turn signal and side repeater (European only) lamps or to all of the turn signal fuses for hazard operation. The driver door switch and passenger door switch also receive voltage from the BCM turn signal supply voltage circuits for the mirror turn signals. The door switches have no function or control of the mirror turn signals other than a pass through connection for the circuits. The audio chime is also activated when the turn signals are ON. The instrument panel cluster (IPC) receives the signals to activate the turn signal indicators over the GMLAN serial data system.
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 Switch parameters while cycling the turn signal switch between the left and right positions. The readings should toggle between ACTIVE and INACTIVE.
- Observe the left turn signal lamps while activating the left turn signals. The left turn signal lamps should illuminate and flash when turned ON.
| ⇒ | 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. |
| ⇒ | If the left turn signal lamps do not flash or flash in a rapid manner, refer to Turn Signal Lamp Malfunction. |
Circuit/System Testing
Turn Signal Lamp Malfunction
- Ignition OFF, disconnect the X4 harness connector at the BCM.
- Verify that a test lamp illuminates between the LT STOP TRN fuse B+ circuit terminal 1 and ground.
- Verify that a test lamp illuminates between the RT STOP TRN fuse B+ circuit terminal 3 and ground.
- Ignition OFF, reconnect the X4 harness connector at the BCM.
- Disconnect the harness connector at the appropriate turn signal lamp.
- Test for less than 5.0 ohms between the appropriate ground circuit terminal and ground.
- Connect a test lamp between the appropriate turn signal control circuit terminal and ground.
- 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.
- If all circuits test normal, test or replace the appropriate turn signal lamp.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| • | Park/Turn Signal Lamp -- Left front terminal C -- with X88/Z88 |
| • | Park/Turn Signal Lamp -- Right front terminal A -- with X88/Z88 |
| • | Turn Signal Lamp -- Left and Right front terminal 3-- with Z75 |
| • | Repeater Lamp -- Left and Right front terminal 2 -- with TR2 |
| • | Tail/Turn Signal Lamp -- Left and Right rear terminal GRD -- with X88 |
| • | Tail/Turn Signal Lamp -- Left and Right rear terminal G-- w/o X88 |
| • | Tail/Stop and Turn Signal Lamp -- Left and Right Upper rear terminal GRD -- with X88/Z75 -- EXP -- E52 |
| • | Tail/Stop and Turn Signal Lamp -- Left and Right Lower rear terminal GRD -- with X88/Z75 -- EXP -- E52 |
| • | Tail Lamp Circuit Board -- Left and Right rear terminal D -- with Z75 + E52 |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| • | Park/Turn Signal Lamp -- Left front terminal A -- with X88/Z88 |
| • | Park/Turn Signal Lamp -- Right front terminal D -- with X88/Z88 |
| • | Turn Signal Lamp -- Left and Right front terminal 1-- with Z75 |
| • | Repeater Lamp -- Left and Right front terminal 1-- with TR2 |
| • | Tail/Turn Signal Lamp -- Left and Right rear terminal MJR -- with X88 |
| • | Tail/Turn Signal Lamp -- Left and Right rear terminal A -- w/o X88 |
| • | Tail/Stop and Turn Signal Lamp -- Left and Right Upper rear terminal MJR -- with X88/Z75 -- EXP -- E52 |
| • | Tail/Stop and Turn Signal Lamp -- Left and Right Lower rear terminal MJR -- with X88/Z75 -- EXP -- E52 |
| • | Tail Lamp Circuit Board -- Left and Right rear terminal B -- with Z75 + E52 -- with EXP |
| • | Tail Lamp Circuit Board -- Left and Right rear terminal E -- with Z75 + E52 -- w/o EXP |
| ⇒ | 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 Switch Malfunction
- Ignition OFF, disconnect the harness connector X1 at the turn signal/multifunction switch.
- Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal F.
- Ignition ON, verify the scan tool Left Front and Rear Turn Signal Switch parameter is INACTIVE.
- Verify the scan tool Right Front and Rear Turn Signal Switch parameter is INACTIVE.
- Verify the scan tool Hazard Lamp Switch parameter is INACTIVE.
- Install a 3A fused jumper wire between the signal circuit terminal E and ground. Verify the scan tool Left Turn Signal Switch parameter is ACTIVE.
- Install a 3A fused jumper wire between the signal circuit terminal D and ground. Verify the scan tool Right Turn Signal Switch parameter is ACTIVE.
- Install a 3A fused jumper wire between the signal circuit terminal G and ground. Verify the scan tool Hazard Lamp Switch parameter is ACTIVE.
- 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 E for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If not the specified value, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If not the specified value, test the signal circuit terminal G 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. |
| ⇒ | 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 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, programming, and setup. |
