For 1990-2009 cars only
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 |
|---|---|---|---|---|
Cellular Microphone Signal | B2455 04 | B2455 04 | B2455 04 | -- |
Cellular Microphone Low Reference | -- | B2455 04 | 1 | -- |
1. OnStar Microphone Inoperative - Caller Cannot Be Heard | ||||
Circuit/System Description
The communication interface module (CIM) provides the cellular microphone with a supplied voltage on the cellular microphone signal circuit. When the microphone is in use, voice data from the user is sent back to the CIM on the signal circuit. The CIM provides a ground for the microphone via the low reference circuit.
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 Testing
- Ignition OFF, disconnect the harness connector at the cellular microphone.
- Test for less than 10 Ω between the low reference circuit terminal A and ground.
- Ignition ON, test for 9.5-10.5 V between the signal circuit terminal B and ground.
- If all circuits test normal, replace the cellular microphone.
| ⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
| ⇒ | If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CIM. |
| ⇒ | If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the CIM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for CIM replacement, setup, and programming |
