Followed test proceedures in Bentley manual. Involves testing resistance and heating/cooling the sensor-(used heat gun and ice water. Hope this helps. Also, if yours is bad you'll know it by the check engine light and by unusually rich behavior-(deposits on plugs or it won't run at all-flooding).Mine did all of the before mentioned but I did not know it (like an idiot I cleared the ECU memory before I checked the codes). I rely heavily on the members of this board for advice on troubleshooting weird things that creep up from time to time.As a last note, I found the Bosch sensor at the dealer for $25.00- cheaper than FCP Groton and a lot faster.