The distributor was replaced, and the optical sensor is in the distributor. I am glad you came up with the low resolution signal idea, and yes I have checked it when hot and cold, at the distributor. The AC signal is there when cold, and disappears when the engine dies. The low resolution signal is the AC voltage measured on terminal A ot the four pin distributor connector. When the connector is pulled out of the distributor, terminal A is the First terminal from the right, Looking at the pins on the connector, with the tab on top. When the engine was hot, after it had died and no resolution signal was available, I checked for a low resolution signal, of which there was none. I then rang out the wire from terrminal A to connector B(black connector) , pin 2 and got 0 ohms when hot(good wire and pin). According to Mitchell, this means the PCM (computer) is bad. I would normally agree with this, but the PCM has been replaced, with the same result. The problem with removing the connectors, on the sensors, is that this may render the same result, as sometimes the computer is lookin for a varing signal, and if an open or short is detected, sees this as an error, and may not run. If anyone knows the sensors, and relays that can shut down the computer when hot, please let me know. Rember, not only does the car die when running and hot, but then will not start, because of the loss of the low resolution signal, although it cranks fine.