This is the symptom everyone has been ignoring, and it's important. First of all, the key's starting position simply tells the ECM that you want to start the GX. It never matters how long you hold the key there, you can barely tap it and it will still start. The ECM keeps cranking until sensors detect a running engine.

So when your extended crank happens, the engine isn't starting as quickly as it should, or the ECM isn't receiving a signal from a crank or cam sensor to indicate that it's running. That's where your research should have begun.

Possibilities:
ECM overheating (probably fried).
Crank or Cam sensor failing.
A/C voltage output from the alternator.

The fact you aren't getting codes is a likely sign that the ECM is going bad or the alternator has a bad diode that is dumping AC voltage onto the electrical system. There are some guides on the web regarding how to check an alternator for AC leakage.

 

Awesome and thanks! Hopefully it is something that simple. Regarding the ECM what should I look for when purchasing? Does it have to be from a 2003? Im finding them for as cheap as $150 and if that is all this ordeal ends up costing me then that will be sweat.

 

Well its not the ECU. I got another one and still nothing. The problem has gotten worse and wont turn over regardless of what ECU is in there. I pulled the Crank position sensor out and checked resistance and got about 2.1 kilohms. Im assuming that is a good reading.

From what I read regarding a bad diode in the alternator is that you will gradually loose voltage at the battery. It has sat for days and sitting at 12.10 volts.

 

Im wondering if it was a bad diode or had AC leakage would it be an intermittent problem though

 

You may have to bite the bullet and take it lexus for a diag to see what they can find and what it would cost to fix it.....Not worth throwing all these parts at it and wasting money

 

A bad diode won't always make your battery go dead. There are several diodes that can fail, and there are different ways they can fail. The diodes rectify the AC from the alternator into DC. If you've got a bad diode it'll allow AC past, which can fry all kinds of stuff. Many bench tests don't check for AC voltage, so you're kind of in a tough spot now that it won't start.

Understand though, the issue isn't really about the AC at this point. You can easily solve that by disconnecting the alternator. It's an issue of something else being fried, and what fried it, whether it was AC leakage, corrosion, or just general old age.

 

Well I just got the alternator out. Had it tested and they said its good.

 

Engine won't start a positive wire again hot to the starter