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1. Car would lose all power randomly when driving.
2. Currently has a no crank, no start. This has been happening on and off. Sometimes it starts fine, sometimes I have the no crank, no start.
I did some testing and the ignition switch seems good. I found that the powertrain relay is not pulling in. Relay measures fine with ohmmeter. There is 12v present to one side of the coil. I’m thinking a signal applies the ground to the other side of the coil which would pull it in and close the contact.
I can’t find what signal is sent to pull in that relay.
My assumption would be the ECU?
Could a bad ECU also cause the complete loss of power problem also?
Is the ECU and powertrain control module the same thing?
Don’t use a multimeter to diagnose non working circuits. Multimeters are designed to not load a circuit and cause damage to sensitive components. You have to load test relays. The main relay in Honda’s caused many problems in the 80s. Maybe Saturn used the same Bosch relay in your car.