Modern automatic transmission are sophisticated pieces of machinery that are made up of several components that work together to shift the vehicle’s gears. They operate using hydraulic pressure to shift the gears, and use electronic solenoids to regulate the pressure of the transmission fluid to control the shifting points. One of these electronic solenoids are the downshift solenoids.
The downshift solenoid controls the transmission shifting from a higher gear to a lower gear, such as when the vehicle is slowing down to a stop. When the solenoid fails or has any issues, it can cause problems with the vehicle’s shifting. Usually a bad or failing downshift solenoid will produce a few symptoms that can alert the driver of an issue that needs to be serviced.
1. Erratic shifting
One of the first symptoms of a bad or failing downshift solenoid is erratic shifting. If the downshift solenoid has any issues, it may cause the vehicle to behave erratically when downshifting. A bad or failing solenoid may cause the vehicle to experience hard or erratic shifting when slowing down or coming to a stop.
2. Late shifting
Another common symptom of a problem with the downshift solenoid is a vehicle that experiences late downshifting. If the downshift solenoid fails or has an issue, the vehicle may experience late shifting when slowing down. The transmission may stay engaged in a higher gear for an extended period of time when it should be downshifting. This will cause the engine to over rev, and may put additional unnecessary strain on the engine and transmission.
3. Check Engine Light comes on
An illuminated Check Engine Light is another symptom of a bad or failing downshift solenoid. If the computer detects a problem with the downshift solenoid circuit or function it will set off the Check Engine Light to alert the driver of the issue. An illuminated Check Engine Light can also be caused by a wide variety of other problems, so having the computer scanned for trouble codes is highly recommended to be certain of what the issue may be.
Downshift solenoids are an important transmission component, and without them, the vehicle will not be able to shift gears properly, sometimes even to the point of rendering the car undriveable. For this reason, if you suspect that your downshift solenoid may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if your car needs a replacement downshift solenoid.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Downshift Solenoid and was authored by Ed Ruelas.