Hyundai Repair: TCM or VSS, vehicle speed sensor, emission control system
QuestionQUESTION: Hi, I have a 99 sonata w/6cyl 2.5 Lrt. I could be driving my car on the highway and suddenly a tremendous buck would occur then the check engine light would come on the the car would come out of overdrive and not shift right. I would pull over and shut the car off and most times it would reset and be fine for awhile, till the next time. I have an autoxray ez-scan 5000. I hooked it up and no codes came up but when I read the operational data it told me the vehicle speed was 11mph and I was parked. When I drove the car the vehicle speed would occasionally jump but return to 11mph. Just for fun I went to an auto zone and with a different code reader the code 0720 (output shaft speed sensor)came up. Ant help would be greatly appreciated. Thank You Mike
ANSWER: Anytime data is present that just doesn't make sense, there's likely a communication issue between the scan tool and the computer. I'd trust the P0720 and replace the output speed sensor (not the vehicle speed sensor).
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QUESTION: HT you were right on the money about the output speed sensor. The car ran well for a couple of days then I got a code 0440 (evap. emission control system malfunction). I really don't know where to begin with this one. Also when I hook up my scanner it still shows 11mph. Should I just ignore that or do I have a further problem. Thanks Mike
AnswerI don't recall seeing this code on a Hyundai, so I checked the service manual. On most vehicles, this is a generic trouble code that simply means there's a problem somewhere in the fuel vapor management system. But according to the service manual, it indicates that the ECM believes the purge control valve to be stuck open. Purge valves are relatively inexpensive and easy to service, so I'd say to replace yours and clear the lamp to see if it returns. If you can blow through the purge control valve while the engine is off, that's definitely a problem-- it should be closed.
