02 mercury cougar 2.5

Put new PCM in car. When I turn the key over several times I get no crank. Eventually it will crank and start. It will run and drive fine. When I park it and turn it off it starts the no crank condition again. Only trouble code I get is a p0743. TCS electrical circuit. I'm lost on this.

Hey Willscohy! Was the PCM replaced in response to this no crank issue? Or, was this issue present before the PCM replacement?

Looking at the diagram, I'd suggest doing some quick checks at the starter relay when you get it to not crank:



With a test light or DMM, with the key in the crank position, we're looking for two power feeds. One at pin 3 from the battery for the load side of the relay, and one at pin 1 from the ignition switch.

If you have those, then we're looking for two grounds. One will be through the starter solenoid winding at pin 4, and the other will be through the park/neutral switch (or clutch switch if it's a manual) and the PCM itself on pin 2. That ground at pin 2 is especially important. If it's there when the engine isn't cranking, then it means that the PCM is allowing starter operation. If it isn't, then we can dig into an anti-theft issue.

Can you hear the starter relay click or anything while you're turning the ignition to the start position while it's a no crank?
Was the PCM replaced for this concern, or did this only begin after the PCM was replaced?
It looks like the PCM switches ground ground to the control side of the starter relay through the park neutral switch (possibly for antitheft, it doesn't look like it would control the ground here to activate the starter) and the ignition switch switches power to the control side of the starter relay (through the starter relay diode)with the ignition in the start position.
I would start checking at the relay the next time it's a no crank.

Cavity 3 in the relay base should be constant battery voltage.
Cavity 5 should be constant ground through the starter.
Cavity 1 should be battery voltage with the ignition in the crank position.
Cavity 2 should be ground with the car in park\neutral and the pcm completing the circuit.
Find out which one is missing during the no crank, and we can take it from there.

Lol, you beat me to it!

I replaced the PCM because of bad drivers. It would crank before the new PCM was put in. I had a locksmith program the keys to the new PCM.