'03 Model:

Open the trunk lid, and remove the OnStar system control compartment cover.
Remove the OnStar system control compartment with bracket.
Remove four screws which installs the OnStar control unit and OnStar system interface unit onto bracket.
Disconnect the 32P connectors from the OnStar control unit.
Inspect the connector and socket terminals to be sure they are all marking good contact.
- If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.
- If the terminals look OK, make the following input tests at the connector.
  - If any test indicates a problem, find and correct the cause, then recheck the system.
  - If all the input tests prove OK, the control unit must be faulty; replace it.
Fig 1: Identifying On Star Control Unit Connector Terminals
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 2: OnStar Control Unit Input Test (Disconnected)

Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 3: OnStar Control Unit Input Test (Connected - 1 Of 2)

Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 4: OnStar Control Unit Input Test (Connected - 2 Of 2)

Courtesy of AMERICAN HONDA MOTOR CO., INC.