J Gonzales Posted April 19, 2022 Report Share Posted April 19, 2022 When I turn on the test feature for radiator fans, ce light, tach converter, or fuel pump i read 0v on the signal wire from the ecu, but when I turn it off on the test feature it reads 12v. Not sure why this is happening. Maybe its made to control normally closed relays? Quote Link to comment Share on other sites More sharing options...
Confused Posted April 19, 2022 Report Share Posted April 19, 2022 There is a very weak pull up to 12v when the output is off. This is why you'll be seeing 12v on the meter. The output, when on, switches the ground signal. This is also why it's important to have most of your accessories powered via an ignition feed, rather than permanent feed. Quote Link to comment Share on other sites More sharing options...
J Gonzales Posted April 19, 2022 Author Report Share Posted April 19, 2022 Im not well versed in ecu stuff so this doesnt make much sense to me. Why would it read 12v when off but not when on? What do you mean by switches the ground signal? Am I supposed to control accessories by relaying their ground instead of their power supply? Whats the difference between an ignition and permanent feed? Quote Link to comment Share on other sites More sharing options...
Adamw Posted April 19, 2022 Report Share Posted April 19, 2022 One side of the device should be connected to 12V, the ecu controls the ground side of the device. Devices such as idle valve, vvt & boost solenoids are connected directly like this: High current devices such as fuel pumps and fans are connected like this: Quote Link to comment Share on other sites More sharing options...
J Gonzales Posted April 19, 2022 Author Report Share Posted April 19, 2022 Okay that makes more sense. Looks like ive got some work to do. Thanks. Quote Link to comment Share on other sites More sharing options...
J Gonzales Posted April 19, 2022 Author Report Share Posted April 19, 2022 Another question, if the ecu is to control the ground of a relay, how would I wire in the tach converter correctly, as it needs a signal from the ecu. It essentially functions as a relay, having a +12v, gnd, sig in and sig out to the tacho. Quote Link to comment Share on other sites More sharing options...
Adamw Posted April 19, 2022 Report Share Posted April 19, 2022 All ecu's work this way. Connect the aux to the "sig in". Quote Link to comment Share on other sites More sharing options...
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