The electronic engine management systems on modern vehicles are made up of sophisticated fuel and ignition systems that work together for the vehicle to run. Both systems are made up of various components that all work together to provide timed fuel and ignition for the engine. One of these components is the automatic shutdown relay, commonly referred to as the ASD relay. The ASD relay is responsible for supplying switched 12-volt power to the vehicle’s injectors and ignition coils, allowing them to provide fuel and produce spark.
In certain cases, the ASD relay will also provide power for the vehicle’s oxygen sensor heater circuit as well as function as an automatic shut down switch that will shut off the fuel and ignition systems when the computer detects that the engine is no longer running. As with most electrical components, the ASD relay is subject to the normal wear and tear associated with normal service life, and when it fails, it can cause problems for the entire vehicle. Usually, when the ASD relay has failed or is having a problem the vehicle will produce a few symptoms that can alert the driver that a problem has occurred that should be serviced.
1. Car starts but immediately stalls
One of the most common symptoms of a bad ASD relay is an engine that will start, but stall out almost immediately, or at random times. The ASD relay supplies power to the vehicle’s ignition coils and fuel injectors, which are some of the most important components of the entire engine management system.
If the ASD is having any problems that interfere with its ability to supply power to the injectors, coils, or whatever other circuits it may feed, then those components may not function properly and problems may arise. A car with a failing or faulty ASD relay may stall immediately after starting, or randomly while operating.
2. Engine does not crank
Another symptom of bad ASD relay is an engine that will not crank at all. As many of the engine management systems are wired together, if any of the circuits that the ASD relay provides power for go out as a result of a bad ASD relay, then it may affect other circuits, one of them being the starting circuit. A bad ASD relay can indirectly, and sometimes directly, cause a starting circuit to not have power, which will result in a no crank condition when you turn the key.
3. Check Engine Light comes on
Another symptom of a possible problem with the ASD relay is an illuminated Check Engine Light. If the computer detects that a problem with the ASD relay or circuit has occurred, it will illuminate the Check Engine Light to alert the driver of a problem. The Check Engine Light can also be activated for a wide variety of other reasons, so it is important to have the vehicle scanned for trouble codes to determine what the exact cause of the problem may be.
As the ASD relay is what supplies power to some of the engine’s most critical engine management components, it is a very important part to the overall functionality of the vehicle. For this reason, if you suspect that the ASD relay has failed, or is having a problem, have the vehicle serviced by a professional technician, such as one from YourMechanic to determine if the car needs an automatic shutdown relay replacement, or if another issue needs to be addressed.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Automatic Shutdown Relay and was authored by Ed Ruelas.