My daughter's '09 ES350 has been acting strangely over the past week. A few days ago, she called because the vehicle wouldn't start, had no dash lights, no power at all. We figured it to be a battery problem, so I went over and jumped it. Started right up and ran like a charm for several days. After a few days, the battery was dead again. My husband jumped the car again and it started up. Later, he tested the battery and alternator, both checked out perfectly. Yesterday, she had been out running around, and just as she pulled into our street all of her dash lights went out (the car continued to run). Once she turned it off, it would not start again.

My husband put a code reader on it (although no check engine, or other lights, were illuminated on the display). He got a C1201 code. After reading a bunch of stuff online, it seems to indicate a problem with the ECM and/or ABS system (but she hasn't had any issues with braking). Other threads indicate it could be a bad key fob, or a bad gas cap. A month ago, she had to replace a coil that went bad, so maybe this issue is somehow related.

My husband is going to put a newer, more advanced, code reader on it tonight to see if any other codes are generated, because the C1201 is a very general code. In the meantime, I'm just wondering if anyone has experienced anything like this, or has some insight into what it may be.

 

First, get a new battery before exploring more exotic and unlikely scenarios. Low voltage from a weak battery triggers a lot of random codes from stuff that relies on enough voltage to work properly. I have seen this many times on several Club Lexus forums. Jump starting a dead battery and driving around does not give it enough charge, you need a charger, however the fact that it died again so soon indicates to me that you need a battery.
A battery is inexpensive and the most likely to fail component. It may have passed your home test, but may still be bad.
To be properly tested it needs a full charge from a charger then a test at Advance Auto on their load tester machine. However, I would just get a new battery and I bet all your other problems go away.

If in the Washington DC suburbs, Satellite Motors And Beahm's Auto Service in Silver Spring are good shops. http://satellitemotors.com/

 

Double check that the battery cables are secure.

 

Yes, and I would add that you need to check both ends of the cables!