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 |
|---|---|---|---|---|
Left Turn Signal Switch Signal | 1 | 1 | 3 | -- |
Right Turn Signal Switch Signal | 2 | 2 | 4 | -- |
Ground -- Turn Signal Switch | -- | 1, 2 | -- | -- |
B+ -- Turn Signal Hazard Flasher Module | 1, 2 | 1, 2 | -- | -- |
Left Front Turn Signal Lamp Supply Voltage | 1 | 1 | 3 | -- |
Right Front Turn Signal Lamp Supply Voltage | 2 | 2 | 4 | -- |
Ground -- Front Park Turn Signal Lamp | -- | 1, 2 | -- | -- |
Left Rear Turn/Stop Lamps Supply Voltage | 1 | 1 | 3 | -- |
Right Rear Turn/Stop Lamps Supply Voltage | 2 | 2 | 4 | -- |
Ground -- Tail/Stop and Turn Signal Lamp | -- | 1, 2 | -- | -- |
B+ -- Left Turn/Trailer Relay | 5 | 5 | -- | -- |
Left Turn/Trailer Relay Control | 5 | 5 | 3, 7 | -- |
Left Trailer Turn Signal Lamps Control | 5 | 5 | 7 | -- |
Ground -- Left Turn/Trailer Relay | -- | 5 | -- | -- |
B+ -- Right Turn/Trailer Relay | 6 | 6 | -- | -- |
Right Turn/Trailer Relay Control | 6 | 6 | 4, 8 | -- |
Right Trailer Turn Signal Lamps Control | 6 | 6 | 8 | -- |
Ground -- Right Turn/Trailer Relay | -- | 6 | -- | -- |
1. Left turn signal is inoperative 2. Right turn signal is inoperative 3. Left turn signal is always ON 4. Right turn signal is always ON 5. Left trailer turn signal is inoperative 6. Right trailer turn signal is inoperative 7. Left trailer turn signal is always ON 8. Right trailer turn signal is always ON | ||||
Circuit/System Description
Turn Signals
Turn signal multifunction switch provides ground for the turn signal switch signal circuits and hazard switch. When either the left or right turn signal switch circuits are grounded, the turn signal hazard flasher module applies battery voltage to the appropriate turn signal and marker lamp assembly, as well as the appropriate turn signal indicator in the instrument panel cluster (IPC), which causes the lamps and the indicator to illuminate.
Trailer Turn Signals
The left and right trailer turn signal lamps operate through separate relays. Battery voltage is supplied at all times to the Left TURN/TRAILER Relay from Circuit Breaker 25 located in I/P fuse block-2, while the Right TURN/TRAILER Relay receives B+ from Circuit Breaker 11 located in I/P fuse block-1.
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
- Command the left and right turn signals ON and OFF using the turn signal multifunction switch. The left and right turn signals and the IPC turn signal indicators should turn ON and OFF when changing between commanded states.
- If all turn signals operate as specified, but the trailer turn signal lamps are inoperative, refer to Trailer Turn Signal Lamps Inoperative.
| ⇒ | If all of the turn signals are always OFF, refer to All Turn Signals Inoperative. |
| ⇒ | If one or more of the turn signals are inoperative, refer to the Turn Signal Circuit Test. |
| ⇒ | If the turn signals are always ON, refer to Turn Signals Always ON. |
Circuit/System Testing
All Turn Signals Inoperative
- Disconnect the harness connector at the turn signal/hazard flasher module.
- Verify that a test lamp illuminates between the B+ circuit terminal 9 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal 10 and ground.
- Connect the harness connector at the turn signal/hazard flasher module and disconnect the X1 harness connector at the turn signal multifunction switch.
- Test for less than 5 ohms between the ground circuit terminal 1 and ground.
- Connect a 3A fused jumper wire between the signal circuit terminal 6 and ground. The left turn signal should cycle ON and OFF.
- If all circuits test normal, test or replace the turn signal multifunction switch.
| ⇒ | 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. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the left turn signal does not cycle ON and OFF, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the turn signal/hazard flasher module. |
Turn Signal Circuit Test.
- Disconnect the harness connector at the inoperative turn signal lamp.
- Test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground.
- Connect the harness connector at the turn signal lamp and disconnect the turn signal/hazard flasher module.
- Connect a 3A fused jumper wire between the appropriate control circuit terminal listed below and ground. The appropriate lamps should illuminate.
- Connect the harness connector at the turn signal/hazard flasher module and disconnect the X1 harness at the turn signal multifunction switch.
- Connect a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. The inoperative turn signal should flash ON and OFF.
- If all circuits test normal, test or replace the turn signal multifunction switch.
| • | Tail Lamp Assembly terminal L |
| • | Park/Turn Signal Lamp terminal B |
| • | Turn Signal and Marker Lamp Assembly terminal 3 |
| • | IPC terminal A8 |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| • | Left rear turn/stop lamps terminal 5 |
| • | Left front turn signal lamps terminal 1 |
| • | Right rear turn/stop lamps terminal 4 |
| • | Right front turn signal lamps terminal 3 |
| ⇒ | If the lamp or lamps do not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the bulb or lamp assembly. |
| • | Left turn signal terminal 6 |
| • | Right turn signal terminal 7 |
| ⇒ | If the turn signal does not flash ON and OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the turn signal/hazard flasher module. |
Turn Signal Always ON
- Ignition OFF, disconnect the turn signal multifunction switch. The turn signals should become Inactive.
- If all circuits test normal, test or replace the turn signal multifunction switch.
| ⇒ | If one or more turn signals remain Active, test the control circuit for a short to ground. If the circuit tests normal, replace the turn signal/hazard flasher module. |
Trailer Turn Signal Lamps Inoperative
- Ignition OFF, disconnect the appropriate TURN/TRAILER Relay.
- Test for less than 5.0 ohms between the ground circuit terminal 86 and ground.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
- Connect a test lamp between the appropriate tractor trailer receptacle harness connector terminal 3 and ground.
- Connect a 3A fused jumper wire between the relay B+ circuit terminal 30 and the control circuit terminal 87. The test lamp should illuminate.
- Connect a test lamp between the relay control circuit terminal 85 and ground.
- Command the appropriate turn signal ON. The test lamp should cycle ON and OFF with turn signal operation.
- If all circuits test normal, test or replace the turn/trailer relay.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | 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 control circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not turn ON and OFF, test the control circuit for an open/high resistance. |
Component Testing
Turn Signal Multifunction Switch
- Ignition OFF, disconnect the X1 harness connector at the turn signal multifunction switch.
- Test for infinite resistance between the control circuit terminal 6 and the ground circuit terminal 1 with the left turn signal switch in the open position.
- Test for infinite resistance between the control circuit terminal 7 and the ground circuit terminal 1 with the right turn signal switch in the open position.
- Test for less than 2 ohms between the control circuit terminal 6 and the ground circuit terminal 1 with the left turn signal switch in the closed position.
- Test for less than 2 ohms between the control circuit terminal 7 and the ground circuit terminal 1 with the right turn signal switch in the closed position.
| ⇒ | If not the specified value, replace the turn signal multifunction switch. |
| ⇒ | If not the specified value, replace the turn signal multifunction switch. |
| ⇒ | If not within the specified range, replace the turn signal multifunction switch. |
| ⇒ | If not within the specified range, replace the turn signal multifunction switch. |
Relay
- Ignition OFF, disconnect the appropriate relay.
- Test for 70-100 ohms of resistance between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- Test for less than 2 ohms of resistance between terminals 30 and 87A.
- Install a 10A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.
| ⇒ | If the resistance is not within the specified range, replace the appropriate relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the appropriate relay. |
| ⇒ | If greater than the specified range, replace the appropriate relay. |
| ⇒ | If greater than the specified range, replace the appropriate relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
