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 X4 Terminal 1 | 2 | 2 | -- | -- |
B+, BCM X4 Terminal 2 | B2615 00 | B2615 00 | -- | -- |
B+, BCM X4 Terminal 3 | 7 | 7 | -- | -- |
Left Front Turn Signal Lamp Supply Voltage | 2 | 4 | 4 | -- |
Right Front Turn Signal Lamp Supply Voltage | B2615 00 | 5 | 5 | -- |
Left Rear Stop/Turn Lamp Supply Voltage | 2 | 6 | 6 | -- |
Right Rear Stop/Turn Lamp Supply Voltage | 7 | 7 | 7 | -- |
Left Turn Signal Switch Signal | 1, 2 | 2 | 2 | -- |
Right Turn Signal Switch Signal | 1 | 3 | 3 | -- |
LF Park/Turn Signal Lamp Ground | -- | 4 | -- | -- |
RF Park/Turn Signal Lamp Ground | -- | 5 | -- | -- |
Left Tail Stop/Turn Lamp Ground | -- | 6 | -- | -- |
Right Tail Stop/Turn Lamp Ground | -- | 7 | -- | -- |
Turn Signal/Multifunction Switch Ground | -- | 1 | -- | -- |
1. All turn signals inoperative 2. Left turn signal malfunction 3. Right turn signal malfunction 4. Left front turn signal malfunction 5. Right front turn signal malfunction 6. Left rear turn signal malfunction 7. Right rear turn signal malfunction | ||||
Circuit/System Description
Ground is applied at all times to the turn signal/multifunction switch from G201. The turn signal lamps may only be activated with the ignition switch in the ON position. The body control module (BCM) controls the vehicle turn signals based on inputs from the turn signal/multifunction switch. With the turn signal/multifunction switch in either the left or right turn position, a ground is applied through the turn signal switch signal circuit to the BCM indicating a turn signal request. When the specific request is seen, the BCM then applies a pulsating voltage through the front and rear turn signal 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
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
- 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 parameter should cycle between Active and Inactive.
- Observe 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 parameter should cycle between Active and Inactive.
- Ignition ON, place the turn signal/multifunction switch in the left turn position. The left turn signal indicator on the IPC should cycle ON and OFF.
- Ignition ON, place the turn signal/multifunction switch in the right turn position. The right turn signal indicator on the IPC should cycle ON and OFF.
| ⇒ | If the parameter does not cycle between the specified values, refer to Turn Signal/Multifunction Switch Circuit Test. |
| ⇒ | If the parameter does cycle between the specified values and the left turn signal is inoperative, refer to the Turn Signal Circuit Test. |
| ⇒ | If the parameter does not cycle between the specified values, refer to Turn Signal/Multifunction Switch Circuit Test. |
| ⇒ | If the parameter does cycle between the specified values and the right turn signal is inoperative, refer to the Turn Signal Circuit Test. |
| ⇒ | If the indicator is always OFF, refer to Turn Signal Indicator Test. |
| ⇒ | If the indicator is always OFF, refer to Turn Signal Indicator Test. |
Circuit/System Testing
Turn Signal/Multifunction Switch Circuit Test.
- Ignition OFF, disconnect the X2 harness connector at the turn signal/multifunction switch.
- Verify that a test lamp illuminates between the ground circuit terminal B and B+.
- 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 G and the ground circuit terminal B. Verify the scan tool Left Turn Signal Switch parameter is Active.
- Install a 3A fused jumper wire between the signal circuit terminal H and the ground circuit terminal B. 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 G 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 Circuit Test.
- Ignition OFF, disconnect the X4 harness connector at the BCM.
- Ignition ON, verify a test lamp illuminates between the following B+ terminals and ground.
- Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
- Test for less than 5.0 ohms of resistance between the ground circuit listed below and ground.
- Connect a test lamp between the supply voltage circuit listed below and the ground circuit .
- Ignition ON, command the inoperative 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 assembly.
| • | B+ terminal 1 |
| • | B+ terminal 2 |
| • | B+ terminal 3 |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the B+ circuit and the respective turn signal circuits for a short to ground. |
| • | Chevrolet front turn signal - terminal 2 |
| • | Pontiac front turn signal - terminal 3 |
| • | Chevrolet and Pontiac rear turn signal - terminal GRND |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| • | Chevrolet or Pontiac front turn signal - terminal 1 |
| • | Chevrolet and Pontiac rear turn signal - terminal Minor |
| ⇒ | If the test lamp is always ON, test the supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp is always OFF, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
Turn Signal Indicator Test
Ignition ON, with a scan tool perform the display test for the instrument panel cluster (IPC) and observe the turn signal indicator.
| ⇒ | If the turn signal indicator illuminates during the test, replace the BCM. |
| ⇒ | If the turn signal indicator does not illuminate during the test or remains 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 |
