Complex! 2006 Lexus SC430, running perfectly. Suddenly missing, scanned, "misfire cyl 5." Couple of days later, running rougher, scanned, "Misfire cyls 1, 3, 5, 7." Couple of days later, wouldn't start, scanned, "Problem with camshaft position sensor circuit, " "Problem with crankshaft position sensor circuit." Checked continuity of both circuits, tested good. Changed the camshaft position sensor anyway, no change. Engine fires very briefly, then shuts off. Stumped!
You may have a bad crank sensor, continuity may be good cold but not hot. Also check your fuel pressure as that as well as a vacuum leak plus any type of ignition or cylinder problem can cause misfires.
August, 23, 2011 AT 7:32 PM
Thanks for the reply. Follow-on to question: This situation felt familiar, and when I thought about it, I recall a time when another Lexus was behaving similarly (not the codes, but the brief start, then shutdown). The problem then was the anti-theft system. I don't remember what was wrong or what I had to do to get it going again. Could that be a possibility? Any suggestions on how to check?
August, 23, 2011 AT 8:11 PM
I have not worked on many Lexus vehicles so I really dont'knowhow to reset the system. However it uses a transponder in the key so if you have another good key try that as the diode in theone you are using may be the problem. My manual I have available doesn't say how to reset the security system so i'm kinda screwed on that. I'm sorry.