kentoby

In my 2009 LS460 I press the brake and get the green light on my start button (normal) and the car cranks for a moment, not long enough to start. I press the button again and get nothing yet all the while my dash light are on, etc. I let the car sit a while and the same thing happens again. Evidently the starter is working so my question is: what is in the circuit that tells the starter to disengage thinking that the car has started? It seems there is a fault in a sensor that talks to the starter. I removed the starter relay and bench tested it and it's fine. What else??

swfla

iTrader: (1)

an OBD reader may give you the answer

kentoby

I'll try that but I don't think OBD is meant for this type of issue.

jud149

Have you "load" tested the battery and checked its posts for good contact?

jmcraney

In your opinion, is the car cranking vigorously or is it cranking sluggishly? And, how long does it crank?

kentoby

Cleaned the posts and charged it overnight. I'm looking for circuit/schematic level input. Please keep in mind, if the car sits it cranks momentarily. this tells me that there is some sort of a reset in the circuit, the same circuit that tells the starter to disengage as if the car has started. The simple stuff has already been done. Thanks

kentoby

It cranks normally for about 1 second, I let it sit a while and it cranks for one second again. Something (a sensor, computer, etc.) is shutting down the starter for a while then letting it work again.

jmcraney

I think the advice from jud149 in post #4, above, should be your next move. Have your battery tested by a battery dealer.

kentoby

The battery is ok, I need to look at components withing the starter circuit. I'll ask a more detailed question: what component in the starter circuit tells the starter that the engine has started and to stop cranking? In a keyed car we simply hold the key in the start position until it starts, in a push button car this is done via sensors, etc,. What is that component? Thanks

LeX2K

The engine computer does this based on the various inputs/sensors. "The battery is ok" is you guessing get it tested.

miket000

Jump the starter relay, see if the starter really spins for longer than a second.

AZGS4

I agree, get the battery tested.

kentoby

Battery good, pulled the starter relay and jumped the terminals, starter turns great with lots of power. Starter relay tests good so it comes down to another component in the starting system.

swfla

iTrader: (1)

After checking the simple basics, I'm thinking a module/cpu or it's connector. Intermittent might be either. Maybe someone has the diagram you're requesting, but I suspect it will show a module between the start button and the starter. I wish I knew which module and where it's located. If your code reader didn't show a problem, going to a shop with Techstream software may give you an answer. Techstream is Toyota/Lexus specific software.

Cape600L

Love when people ask for help, numerous people take their time to respond, often with the same diagnostic process and OP ignores said advice and just wants to go about it their own way. Blows me away..