1. Home
  2. Articles
  3. Symptoms of a Bad or Failing ECM-Power Relay

Symptoms of a Bad or Failing ECM-Power Relay

ECM-power relay

The ECM, or electronic control module, is the computer responsible for controlling all of the engine management functions. It is the central control unit of most vehicles and controls a variety of functions, such as electrical system power distribution, emissions, ignition, and fuel systems. It is a very important, if not the most important component of a modern engine management system, and just the same as any other important electrical component it is powered through a relay.

The ECM power relay is the relay responsible for sending power to the ECM. If the relay fails, or has any issues, it can cause the vehicle to have all sorts of problems, and may even render it undriveable. Usually a problem with the ECM power relay will produce a few symptoms that can alert the driver of a problem that should be serviced.

1. No power when the key is inserted

One of the first symptoms of a problem with the ECM power relay is no power when the key is inserted. If the ECM power relay fails it can cut off power to the entire vehicle. A failed relay will disable the dash lights and warning chimes that normally come on when the key is inserted into the ignition, and will probably be unable to start or turn over the vehicle.

2. Engine will not start

Another common symptom of a problem with the ECM power relay is an engine that will not start or turn over. The fuel and ignition systems, as well as several other engine management functions, of many vehicles are controlled by the ECM. If the ECM or it’s relay fail, the entire engine management system will be left without power and will not function as a result. A bad relay may cause the vehicle to crank, but not start, or sometimes not even crank at all.

3. Battery drain or dead battery

A failed ECM power relay can also cause a battery drain or dead battery. If the relay shorts it can leave power on to the computer, even when the vehicle is turned off. This will place a parasitic drain on the battery, which will eventually cause it to go dead.

The ECM power relay is one of the most important relays as it provides power for the vehicle’s computer system. Without it the entire engine management system will be disabled and the vehicle will not run. For this reason, if you suspect that your ECM power relay may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the relay should be replaced.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Still not sure about your car's issue?
Diagnose your car
What kind of issue are you experiencing?
Brakes are squeaking
Car is not starting
Car is overheating
Car is shaking (vibrating)
Fluids are leaking
Heating and A/C
Smoke or steam is coming out of the car
Warning light is on
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222...
P0608 OBD-II Trouble Code: Control Module VSS Output "A" Malfunction
P0608 means there is an malfunction in the vehicle speed sensor A control module often due too faulty speed sensor or shorted electrical wiring.
What it Really Costs to Maintain a Standard Car vs Luxury Car
Luxury cars are more expensive than a standard car off the lot, and maintenance costs more. An Acura TL costs $100 more per year than a Honda Accord.

Related questions

Q: 98 Chevrolet Tahoe cranks but won't start.

Hi there. If your fuel pressure is normal (35 psi or higher) then check the spark plugs and see if they are getting burn spots. If they have burn spots, then the injectors may not be working. If the fuel...

Q: Can you recommend a place for 4 wheel alignment? ... with a lifetime warranty

A lifetime warranty is a gimmick designed to get you to buy an alignment but, of most relevance, the offering or existence of such an exaggerated warranty has no relationship WHATSOEVER to the likelihood of a shop actually following the...

Q: My car is experiencing intermittent low beam headlight malfunction

The headlights on this vehicle are controlled by a multiplex integrated control unit (MICU) located under the left side of the dash on fuse panel. The MICU contains all the headlight controls inside as an assembly and the low beam...