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 |
|---|---|---|---|---|
Body Control Module (BCM) 3 Fuse B+ Supply | 1 | 1 | -- | -- |
Body Control Module (BCM) 5 Fuse B+ Supply | 1 | 1 | -- | -- |
Body Control Module (BCM) 6 Fuse B+ Supply | 1 | 1 | -- | -- |
Hazard Switch Signal | 2 | 2 | 2 | -- |
Left Front Turn Signal Lamp Supply Voltage | 1 | 1 | 1 | -- |
Right Front Turn Signal Lamp Supply Voltage | 1 | 1 | 1 | -- |
Left Rear Turn Lamp Supply Voltage | 1 | 1 | 1 | -- |
Right Rear Turn Lamp Supply Voltage | 1 | 1 | 1 | -- |
Left Tail Lamp Outage Detection Signal | 4 | 4 | 4 | -- |
Left Turn Signal Switch Signal | 3 | 3 | 3 | -- |
Right Tail Lamp Outage Detection Signal | 4 | 4 | 4 | -- |
Right Turn Signal Switch Signal | 3 | 3 | 3 | -- |
Hazard Switch Ground | -- | 2 | -- | -- |
Left Rear Stop/Turn Lamp Ground | -- | 1 | -- | -- |
Left Repeater Lamp Ground | -- | 1 | -- | -- |
Right Repeater Lamp Ground | -- | 1 | -- | -- |
Right Rear Stop/Turn Lamp Ground | -- | 1 | -- | -- |
Turn Signal/Multifunction Switch Ground | -- | 3 | -- | -- |
Turn Signal Lamp - LF Ground | -- | 1 | -- | -- |
Turn Signal Lamp - RF Ground | -- | 1 | -- | -- |
| ||||
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. Ground for the left and right front turn signal lamp is supplied at G104. Ground for the rear turn signal lamps is supplied at G402 for the left and G401 for the right. For more detailed information concerning turn signal lamp operation refer to Exterior Lighting Systems Description and Operation .
Reference Information
Schematic Reference
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Diagnostic Aids
The tail lamp outage detection circuits are low current B+ circuits supplied by the BCM. For purposes of testing, a test lamp connected between the outage detection circuit and ground will not illuminate due to the low current.
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.
- Ignition ON, observe the left turn signal lamps and turn signal indicators on the IPC while activating the left turn signals. The left turn signal lamps and indicators should illuminate and flash when turned ON.
- Ignition ON, observe the right turn signal lamps and turn signal indicators on the IPC while activating the right turn signals. The right turn signal lamps and indicators 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 turn signal indicators are inoperative, refer to Turn Signal Indicators Malfunction. |
| ⇒ | If the left turn signal lamps and indictors illuminate but flash in a rapid manner, refer to Tail Lamp Outage Detection Malfunction. |
| ⇒ | If the left turn signal lamps and indictors illuminate but flash in a rapid manner, refer to Tail Lamp Outage Detection Malfunction. |
Circuit/System Testing
Turn Signal Switch Malfunction
- Ignition OFF, disconnect the harness connector at the turn signal/multifunction switch.
- Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal C.
- Ignition ON, verify the scan tool left turn signal switch parameter is INACTIVE.
- Verify the scan tool right turn signal switch parameter is INACTIVE.
- Install a 3A fused jumper wire between the signal circuit terminal D and ground. Verify the scan tool left turn signal switch parameter is ACTIVE.
- Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool right turn signal 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 D for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If not the specified value, test the signal circuit terminal A 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 C4 harness connector at the BCM.
- Ignition ON, verify that a test lamp illuminates between the BCM 3 fuse voltage supply circuit terminal 2 and ground.
- Ignition ON, verify that a test lamp illuminates between the BCM 5 fuse voltage supply circuit terminal 1 and ground.
- Ignition ON, verify that a test lamp illuminates between the BCM 6 fuse voltage supply circuit terminal 3 and ground.
- Ignition OFF, reconnect the C4 harness connector at the BCM.
- Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
- Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms of resistance between the ground circuit and ground.
- Connect a test lamp between the control circuit and the ground circuit.
- 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, test or replace the appropriate turn signal lamp assembly.
| ⇒ | If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | 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. |
Tail Lamp Outage Detection Malfunction
- Ignition OFF, disconnect the harness connector at the appropriate rear tail lamp assembly.
- Ignition ON, test for B+ between the outage detection circuit terminal C and ground.
- Ignition ON, connect a test lamp between the outage detection circuit terminal C and ground. The test lamp should not Illuminate.
- If all circuits test normal, test or replace the tail lamp assembly.
| ⇒ | If the measured voltage is less than B+, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp illuminates, test the signal circuit for a short to voltage. 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. |
Component Testing
Tail Lamp Assembly
- Ignition OFF, disconnect the harness connector at the appropriate rear tail lamp assembly.
- Test for infinite resistance between the outage detection terminal C and the ground terminal D at the tail lamp assembly.
| ⇒ | If not the specified value, replace the tail lamp assembly. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM or IPC replacement, setup, and programming |
