What to know about the ECM-Power Relay:

Vehicle development has evolved over the past several years to a point where it seems every vehicle function is controlled by a computer, right down to the engine itself. This is actually the case for the engine and its related functions as it is controlled by the engine control module, or ECM. The ECM monitors and adjusts operation and power distribution to the fuel supply and injection systems, engine timing, exhaust gas recirculation, emissions, ignition system, and several other systems. In order to dispense power to run these other systems, the engine control module requires power itself.


The power distribution center, or fuse block, positioned under the hood houses most or all of the vehicle’s fuses and relays. It contains a relay for the ECM that is powered up when the ignition key is turned to the on position. This ECM power relay acts as a switch that supplies power to the ECM. When the ignition is turned off, power buttons inside the ECM relay and it no longer takes battery power. If the ECM power relay stops switching as it should, you will experience vehicle problems. When the relay is stuck open, no power will be supplied to the engine control module and the vehicle won’t start. If the relay is stuck closed, constant power will be sent to the ECM even with the engine turned off and the battery will drain.


Facts to Note:


The battery should be detached any time the electrical system is being repaired.

There are several problems which can cause your vehicle not to start, with the ECM power relay being one of them. Have the problem analyzed by one of your expert technicians.

How to Fix:

The ECM-power relay is confirmed that it needs to be changed. The relay is located in the engine main fuse relay control box.


The faulty ECM-power relay is detached from the control box by pulling it straight up and out of socket.


The new ECM-power relay is fixed into the socket and the engine scanned for codes.


The engine is started and the ECM-power relay is tested for appropriate operation.


The vehicle is road tested for proper operation of the ECM-power relay and is then checked for codes.


Our Proposal:

The ECM power relay should last the lifetime of your vehicle unless there is a power distribution problem or moisture that causes it to fail. If your vehicle won’t start, get one of your expert technicians analyze the problem and change the ECM power relay if necessary.


Common symptoms indicating you may need to change ECM-Power Relay:

Engine will not start when the key is turned.

Engine doesn’t turn over when ignition is on.

Check Engine light is on.

Battery drain which may leave it weak or dead.

Importance of this service:


Although it is extremely unlikely the ECM relay will cause your vehicle to stall or create a safety concern, your vehicle may not start or the battery may die while the ignition is off. In either case, you will need to change the ECM relay.