The Project Pad

to start im using an econoseal ECU with a jumper harness i made to make it PNP with my AAN harness. i originally created a motronic bench harness to test ECU's after i did modifications without having a car as well. so i hooked all this up to my bench setup along with the a USB to serial converter to my tower in my work bench and the ECU connects with VEMStune with no problems. my problem is when i put it in my car connected to the factory engine harness it cannot connect with my either of my laptops. i even tested it with my laptops on the bench harness and i get no communication but as soon as i hook it to the tower it picks up the ECU right away. im using the same USB to serial converter on every case and i have all 3 computers configured to use the same com port for the USB serial converter. whats going on here? is my ECU locked to a single PC? the tower was the first PC i hooked it to too.

What operating systems? Drivers installed correctly? I just picked up a new small laptop on windows 8 and had to buy a new usb-serial adapter cable because my old one that worked with everything up to windows 7 doesn't with windows 8. here's the one I picked up:

http://www.amazon.ca/gp/product/B00425S ... UTF8&psc=1

actually i solved it after posting this. i forgot to add the ground from pin 5 of the serial port to the ECU. for some odd reason it would work fine with the tower but not my laptops.