I have a 2003 L300 motor turns over when I try to crank it but will not crank. Seems there is no fire, (tried starting fluid) up until yesterday fuel gauge was moving when key was turned now not so much. Tried putting code reader on car and it is not connecting, therefore will not give me any codes. My question is does the BCM control the spark, or is it the ECM or could they both be bad?

 

first things first.
.."motor turns over when I crank it but it will not crank"..... Huh?

1) do you mean you turn the key the motor cranks (spins) but does not FIRE?

2) Have you pulled a plug and grounded the end of it to the frame or other non-painted metal grounded surface?

3) "fuel gauge was moving before but not so much" . Probably running down battery

4) I'm an S series guy, but I believe the BCM manages everything except running the engine. So I would think the ECU controls spark, fuel, air fuel ratio, etc.

5) Get the battery recharged
6) What is the status of the security light when you are trying to start the car? Solid? Blinking?

Answer the above and we'll go from there.
The diag port is prob a fuse

 

Another one hit wonder?

 

I think derf hurt someones feeling by asking all of those "technical" questions. Oh, well.

 

I think if I know where to start confirming basic info and beginning basic troubleshooting, I'm not playing 20 questions. You come to a forum for help from those who theoretically know more than you. Asking an open ended question that is significantly off the mark requires basic questions and confirmations with a few diagnostic questions to boot.

I may not always come across smelling like flowers but if you don't understand the answers I typed or the requests for info , then just say so. If you choose to walk away that's up to you. Maybe got the same questions on another forum and engaged there.

Whatever.