3sgte shuts off when fans turn on Options

[Arturio55]

Usdm 95 celica Gt.
Just finished a 3rd gen 3sgte swap and ran the top mount intercooler along with st205 pump and heat exchanger. Did the wiring myself. Cut hole in firewall for harness.

For some reason, when the car reaches operating temperature and the fans kick on, the ecu will lose power and the car shuts off. It doesnt bog down, it just shuts off as if i killed the ignition.
When i put the key to the "on" position, the check engine light wont show and i cant start the car.
Once the fans turn off, the check engine light comes back on and i can start the car again until this issue happens again.

I have no clue on how to remedy this issue. Replaced alternator. Switched ecu. Unplugged different coolant temp sensors. Unplugged fan relays. Unplugged main relay. Checked all wiring multiple times. Even if the fans themselves are unplugged the ecu still loses power momentarily.
I did everything right yet this keeps happening. Please help

This post has been edited by Arturio55: Mar 12, 2016 - 8:25 PM

[Bitter]

I'll bet you missed a ground somewhere and the fan is pulling too much power through a ground and the ECM is dropping below running voltage. Double check all your grounds and double up the ECM grounds to a good body ground. I've seen this issue on other kinds of cars with rotten ground wires, some high amp device comes on and other things stop working.

[Arturio55]

I'll bet you missed a ground somewhere and the fan is pulling too much power through a ground and the ECM is dropping below running voltage. Double check all your grounds and double up the ECM grounds to a good body ground. I've seen this issue on other kinds of cars with rotten ground wires, some high amp device comes on and other things stop working.

Replaced main ground last night. Connected to tranny and radiator support like stock.
Have one ground from alternator bracket to strut mount. Never touched the one behind manifold

Also checked all 4 ecu grounds with volt meter, they're working fine

This post has been edited by Arturio55: Mar 12, 2016 - 9:01 PM

[Bitter]

What do they read when the fan is running?

[Arturio55]

What do they read when the fan is running?

Around 11.9- 12, but of course the engine was off at that point and the fans drawing current

[Bitter]

http://www.fme-cat.com/Docs/1519.pdf Test voltage drop for the ECM powers and grounds when the fans are running. You can force the fans on by jumping the relay or by unplugging the fan switch.