Engine fan control output

[Fleetman13]

I had an ECM that had a bad fan circuit driver. So it’s very possible this could be the case. I’d check all your power and grounds going into the ECM and make sure they are good. Make sure the circuits can carry a load (have integrity) don’t use a LED test light or a power probe they can send you down a rabbit hole some times. If all that checks out back probe you’re OEM harness at the ECM and make sure it’s sending out the correct voltage. If it’s not I’d load test your wires from your ECM to your fan if they test good then it’s a good possibility it’s the ECM. I wanna say the one I had issues with put out like 8.7 volts or something like that never could fire off the fan but it never had any other issues other than that. Also if you don’t have a circuit load tested then just wire up a head light bulb in between your circuits and if it will light that bulb your circuit has plenty of integrity.