Access shows only "ODBC--connection to … failed" (3151)

When opening or linking a table, Access reports error 3151 “ODBC–connection to '…' failed” without saying why.

The driver knows the actual reason; this page shows where to find it.

Access and DAO, both bitnesses; other applications receive the cause as a driver message.

On a failed connection attempt, Access shows only its own number. Access discards the actual message from the driver or the service – wrong password, expired or blocked key, missing second factor, untrusted certificate, unreachable service, invalid setting in the connection.

1. Turn on the driver's tracing, restart Access, and open the table again.

2. Search the file for the line SQLDriverConnectW and the message after it. Common reasons:

   Message	Continue with
   “… UntrustedRoot …”	08S01 "UntrustedRoot"
   “Der persönliche Schlüssel ist unbekannt.” / “… ist abgelaufen.” / “… ist gesperrt.” (The personal key is unknown. / … has expired. / … is blocked.)	have a new key issued; Sign in with a personal key
   “The driver sends a password only over https or to this computer.”	switch URL to https
   “The connection doesn't name the service's address (URL).”	add URL to the connection or data source
   HTTP 401 with Wkl-Totp, without a dialog	the application allows no dialog; specify TOTP/SESSION

3. If the trace names only an HTTP status, look in the service's log at the same time.

After the correction, the table opens; after SQLDriverConnectW, the trace shows the response HTTP 200 to $metadata.

• Driver connection string: Exceptions
• Turn on tracing