The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Can I power up the ECM without an engine attached?

kipps · 01-18-2019, 10:22 PM

Based on my schematics, the run/crank relay provides an ignition hot source to the ecm. The ecm in turn, activates the powertrain relay, which "turns on" the engine sensors and components. I want to know if the ecm will automatically power up that relay when it gets a key on signal, as does it need a data signal to do so.

If you didn't follow that mumble-jumble, don't sweat it. On to the question...

Can I provide 12 volts to the appropriate pins on the ecm, and read the output voltages on various pins without an engine attached? Or is this somehow dangerous or ill advised?

I would be doing this through the stock harness and fusebox. So I won't be just blindly pushing alligator clips into the ecm pins...

01-18-2019, 10:22 PM	#1
kipps Registered User Join Date: Jul 2014 Location: North-central Virginia Posts: 1,099	Can I power up the ECM without an engine attached? Based on my schematics, the run/crank relay provides an ignition hot source to the ecm. The ecm in turn, activates the powertrain relay, which "turns on" the engine sensors and components. I want to know if the ecm will automatically power up that relay when it gets a key on signal, as does it need a data signal to do so. If you didn't follow that mumble-jumble, don't sweat it. On to the question... Can I provide 12 volts to the appropriate pins on the ecm, and read the output voltages on various pins without an engine attached? Or is this somehow dangerous or ill advised? I would be doing this through the stock harness and fusebox. So I won't be just blindly pushing alligator clips into the ecm pins...