The following is a sample error response from the UPS OnLine Tools server.  Please see your Developers Guide for a complete list of error responses.

<?xml version="1.0"?>
<TrackResponse>
  <Response>
    <TransactionReference>
      <CustomerContext>guidlikesubstance</CustomerContext>
      <XpciVersion version=”1.0001”/>
    </TransactionReference>
    <ResponseStatusCode>0</ResponseStatusCode>
    <ResponseStatusDescription>Failure</ResponseStatusDescription>
    <Error>
      <ErrorSeverity>Hard</ErrorSeverity>
      <ErrorCode>10002</ErrorCode>
      <ErrorDescription>The XML document is well formed but the document is not valid</ErrorDescription>
      <ErrorLocation>
        <ErrorLocationElementName>TrackRequest/TrackingNumber</ErrorLocationElementName>
      </ErrorLocation>
    </Error>
  </Response>
</TrackResponse>