'03 Model:

Open the trunk lid, and remove the OnStar system control compartment assembly cover.
Remove the OnStar control compartment with bracket.
Remove the four screws which install the OnStar control unit and OnStar system interface unit onto bracket.
Disconnect the five connectors from the OnStar control unit and OnStar system interface unit.

Fig 1: Disconnecting OnStar System Unit Connectors
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Release the clip on the bracket, and remove the OnStar system radio frequency modulator unit.
Disconnect the 25P connector (A) from the OnStar system radio frequency modulator unit (B).

Fig 2: Identifying OnStar System Radio Frequency Modulator Unit Connector Terminals
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Reconnect all connectors to the OnStar control unit and OnStar system interface unit.
Inspect the connector and socket terminals to be sure they are all making 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 3: OnStar System Radio Frequency Modulator Unit Input Test (Disconnected)

Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 4: OnStar System Radio Frequency Modulator Unit Input Test (Connected)

Courtesy of AMERICAN HONDA MOTOR CO., INC.