TriWav

Hey guys, dec 23 2021 my car was running perfect until out of nowhere it just stop starting, I’ve had a mechanic replace spark plugs, ignition wires and coils, fuel pump assembly, cam and crankshaft sensor. Still no start, mind has been over the place and I lost my master key. Called multiple locksmiths to make me a key said they need the master key because they can’t communicate with the ECU. So next thing I noticed is that security light always flashing even when the key is in the ignition so I towed it to the Lexus dealership and the ran the machine to try and find the issue and the couldn’t communicate with the ECU as well so I bought and ECU with a master key, replaces the transponder key amplifier, ignition lock cylinder, and the ignition switch and that didn’t work as well. How do I remove or disable the stupid anti theft system and should I start with OBD2/ DLC3

TrueGS300

That's a lot of new stuff. Is the security light still flashing as if that might still be the issue? I'm wondering if maybe it's something outside the box, like could you have possibly went to fuel up and put diesel in? No matter what you replace, it would still not start if that's the case. Have you actually paid for a diagnosis or have you requested the parts to be replaced each time? Maybe let someone really figure it out with real diagnostic equipment.

TriWav

That’s the thing. The Lexus dealership said they couldn’t get a reading from the ECU through the machine and all my fuses are good. Yes my light is still flashing. One thing I noticed is that I tested the voltage from the transponder key amplifier to the ECU and I’m only getting 1V. Can anyone tell me if that’s the right voltage I don’t have the service manual. Also I tested the OBD data link pin and I’m getting 4.5V

TriWav

Lexus told me that it was the ECU so I bought an ECU with a programmed key and that didn’t work. They did a full diagnostic for like a whole day and those parts I’ve replaced were before I took it to Lexus and no. I’ve always put premium in my car

TrueGS300

You shouldn't have to pay for something that they told you it needed and didn't fix it. Unfortunately if the "Lexus dealership" has failed in diagnosing the car, there's not much we are going to be able to help you out with here. They have the ability to test anything we can possibly think up.

TriWav

Honestly I feel like they did a half *** job because I had an appointment at 1120am and didn’t get seen until 400pm. They didn’t want to work on my car

LeX2K

First thing you need to do is get the key programmed to the ECU there are services on Ebay that do this
https://www.ebay.com/itm/184990003005

I am not vouching for the above it came up in a search. Better if you can find a locksmith local to you but that can be difficult. My gut says there could be other electrical problems thanks to the mechanic that did all that work on your car.

Margate330

We've all done dumb things and when it rains it pours, murphy's law. lol
You don't need anyone to tell you that losing the Master Key while the car had a "no start" condition made this diagnostic exponentially more complicated.

May explain why the dealer could have brushed you away with the classic "replace ECU" theory- it may need an ecu and maybe not- no way to know yet and this is an educated guess but thin evidence so far with a flashing security light now contributing to the "no start" condition.
And the first tech who worked on your car was clearly out of his league replacing cam & crank sensors without scoping it first, fuel pump, plugs, wires , etc and handing you back a non-running car.

To get back to a place where a diagnostic can proceed I can think of 2 solutions, hopefully others have more...
1) Tear the house apart and find that master key!!!
2) Do whatever it takes and satisfy the immobilizer security from a place of knowing and not guessing- so the "no-start" diagnostic can proceed knowing it's not immobilized.

dwoods801