fast question

[cojo1]

Does anyone know if the ecu sends a hot to the negative side of the fuel pump and fan relays? I have the bank to bank system and checked both negative sides which were hot when you check them to ground! I was under the impression that the ecu sent a negative signal to the negative side of the relay. *when I checked these the car was off*!

 

[cojo1]

anyone?

 

[TurboTR]

You'll see that because the load is just a relay coil with low resistance, and one side is connected to 12v. So when the ecu output is OFF and you probe either side of the load you just see straight through to 12v. The ecu uses low side drive, meaning it switches to ground when "ON". In the ON case you'll see low voltage, near ground on the ecu side of the load, and still 12v on the other side.

TurboTR

 

[cojo1]

thanks!