Poweer to ECU
Thread Starter
Joined: Mar 2014
Posts: 699
Likes: 59
From: Alamogordo, NM
Poweer to ECU From time to time while working on the '39 and while parked over night at a rod run I kill power with a master cut off switch. Is this on and off in any way detrimental to the ECU?
As I understand it no. What I have heard is that disconnecting power will erase fuel trim memory codes that will re-learn once driven.
Stated in my PSI wiring instruction is to never power up or down with the ignition key on or damage "can" occur.
Stated in my PSI wiring instruction is to never power up or down with the ignition key on or damage "can" occur.
TECH Fanatic
Joined: Dec 2017
Posts: 1,467
Likes: 265
From: Bossier City, Louisiana
Kinda' depends on the ECU, I think. For the roughly 1999 to about 2007 P01 and P59 PCM devices, there are two power input wires. One is the boot up power "operating" 12 volt input. This is what gives it power to actually run. Kill this input and the PCM shuts off operation of the vehicle. No harm done.
The other is the PCM memory keep alive wire. This power retains the learned memory parameters for the electronic transmission and what it takes for the engine to start easily and idle correctly. This wire should be on all the time and it only consumes a tiny amount power - won't run your battery down anytime soon. If you kill power to this wire, your vehicle will possibly be a little harder to start, won't idle correctly right away and the transmission shift feel might be a little different.
But no permanent harm done to your vehicle or the PCM.
Rick
The other is the PCM memory keep alive wire. This power retains the learned memory parameters for the electronic transmission and what it takes for the engine to start easily and idle correctly. This wire should be on all the time and it only consumes a tiny amount power - won't run your battery down anytime soon. If you kill power to this wire, your vehicle will possibly be a little harder to start, won't idle correctly right away and the transmission shift feel might be a little different.
But no permanent harm done to your vehicle or the PCM.
Rick
