Please note, that misdiagnosis of a good working TCU is one of the primary reasons we get these units returned. We no longer accept returns on these units without a 30% restocking fee and there are NO refunds on our original shipping cost. We test all units we possibly can, and will test any returned units. All units we sell are operational units that came out of crash damaged salvage cars. Unlike most sellers on ebay, we never sell ECU's from no-start cars or from flood damaged cars!