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 |
|---|---|---|---|---|
Signal | 2 | 1 | -- | -- |
Low Reference | -- | 3 | -- | -- |
1. Talk Switch inoperative 2. Talk Switch inoperative, scan tool displays active at all times. 3. All Headlamp Switch functions inoperative | ||||
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Switch not pressed Parameter Normal Range: Inactive | |||
Signal | Active | Inactive | Inactive |
Low Reference | Inactive | Inactive | -- |
Circuit/System Description
The OnStar® talk switch, if equipped, is incorporated with the headlamp switch. The body control module supples a B+ input signal to the switch. When the switch is pressed, the signal is pulled low through the switch to the headlamp switch low reference circuit in the body control module. When the body control module senses the signal is pulled low, a serial data message is sent to the communication interface module to start voice interaction with the OnStar® system.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
OnStar Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, observe the body control module scan tool talk switch input parameter while pressing and releasing the talk switch. The reading should change between inactive and active.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the headlamp switch.
- Verify a test lamp illuminates between the low reference circuit terminal 3 and B+.
- Ignition ON, verify the body control module scan tool talk switch input parameter is inactive.
- Install a 3A fused jumper wire between the signal circuit terminal 10 and the low reference circuit terminal 3. Verify the body control module scan tool talk switch input parameter is active.
- If all circuits test normal, replace the headlamp switch.
| ⇒ | If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the body control module. |
| ⇒ | If not the specified value, test the signal circuit terminal 10 for a short to ground. If the circuit tests normal, replace the body control module. |
| ⇒ | 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 body control module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for body control module replacement. |
