Originally Posted by EuroWill

I would check for continuity between the main fuse and the ECM. I am on my iPhone so I cannot look up the wiring diagram on TIS. Thus, I cannot provide the which pins/connectors to check. I suspect the ECM is fried - that is what usually happens when a battery is installed backwards.

Probably the best course or action is to check EVERY (not kidding) fuse in the fuse blocks. I have seen seemingly unrelated fuses cause very strange issues. Additionally, make sure you didn’t burn up any grounds or leave any grounds loose.

Sorry for the less than helpful response earlier - I was irritated with my wife when I posted it.

Will

Originally Posted by MDMXLX

Sorry for the late wrap-up on this, I've been driving the wheels off the car!

I hadn't found the fusebox in the driver's kickpanel before I started this thread. In my car, the cover (and all the codes printed on it for what circuit is what) is missing for this particular fusebox. But, there was ONE fuse blown. A 5 amp fuse.

The car started on the first try after replacing that 5 amp fuse!

THANK YOU to all of you who replied to this thread, you saved me days of time and HUNDREDS of dollars in cost which I was resigned to spending to get the ECU repaired.

THANK YOU THANK YOU THANK YOU!!!!!

Originally Posted by swfla

Glad you were able to add a lot of good info to this thread. We all get aggravated and when you acknowledge it, it's good karma for everyone involved!

Originally Posted by TrueGS300

Interesting conflict of information here. In my experience as a tech, fuses always blow before ECU's.. just saying. But I guess some unicorns must happen at the Lexus dealership.. I've replaced dozens of main fuses and primary circuit fuses for backwards battery installs/ jumps. Never an ECU. Glad for the OP that it was just a fuse.

Originally Posted by swfla

Great news! The reason we helped you figure it out is because folks like you, report back on what the outcome was. That encourages us to help more people. Without feedback, relationships/forums fail.