I have a 2006 tC and it will randomly not start will turn over but won't fire no codes except upstream oxygen sensor code, if I keep clearing the codes it will start and runs great as long as the car is running I have no problems checked all the fuses,
I will get a no communication with the ECM once in awhile when no start happens but then it will connect and will start after a few code clears, this is random most times i have no problems and will run and start great, wanted to see if anyone had any idea's.

I was thinking maybe ECM or some other issue.

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Toyota starters have a tendency to overheat. Does it only not start up after a drive?
I had a starter in a Corolla that started heat soaking and just wouldn't start the car until it cooled down enough.

I had it bench tested three times and it never failed. Finally swapped it out and problem solved.

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What is the code number?

 

The issue I'm having has to do with the immobilizer system that's why i haven't gotten any codes, as long as I don't let the battery die and a new key fob I haven't been having as many issues. Just an update if anyone has any issues. When I run the scanner it seems to think there's no key and if I take the key and put It back a few times it will see the key and start then usually don't have any problems or comes and goes.

 

Is your key fob battery fresh? Have you taken the fob apart to inspect the battery connections for damage or tarnish?

 

I have a new key and battery it still has the issue mainly when it sits overnight if I've been driving it will start every time no problem. If I leave the key in the ignition for over 10 minutes it will start something to do with it not recognizing the key. Still haven't figured it out. It's not the ECU

 

Have you checked your car battery voltage?

 

Has a brand new battery and charging good. It starts fine after I let it set with key on usually only happens after sitting all night. Once I drive the car it does not have any more issues.

 

@monkey 5787, The voltage battery can be on the low side, and there is not enough amperage. Check the Battery connection poles (- +) (for interior bad surface connection -including the Ground), then check the starter electric wire connection for any corrosion, or wrong coverage. Also, some electrical car specialists check the gauge of the wires. Hidden switches/fuses/connectors/extensions mall function.