The smog tester at a "Test Only" station failed to pass my 1997 V90 with 45K miles upon returning for a retest. The exact message on the report read: This vehicle failed the MIL/Check engine light due to failure to successfully complete all OBD self tests. All other tests were OK. The same station fialed the initial testing of the car just an hour before due to fault code PO500, Vehicle speed sensor malfunction. In the meantime I took the car to an independent Volvo repair garage and the technician connected his readout device, verified that the speedometer was working OK and cleared the code at which time the check engine light went off. What does the speed sensor have to do with emission control in the first place and why did the smog tester fail it again after it was verified to be OK. This took place 5 days ago and the check engine light has remained off. What recourse do I have with the smog station. I don,t wish to pay another $50. for another test when I don't believe there was anything not working properly in the first place. Any responses will be appreciated.