Some vehicle problems can be difficult to diagnose. The transmission solenoid is a lever that keeps your car or truck in the correct gear and prevents the transmission from switching to drive, reverse or another gear. Without knowing the symptoms of a bad transmission solenoid, it can be hard to tell if the problem is with the solenoid or transmission itself.
Shifting Into Drive or Reverse
One possible sign of a bad transmission solenoid is when your vehicle has trouble shifting into drive or reverse. Normally, when you start your car or truck, you're able to shift into drive or reverse right away. With a bad transmission solenoid, the vehicle could have a delay of a few seconds, or even take several minutes to warm up and operate properly. During this delay, the vehicle will act similar to how it behaves in neutral. It won't stay in park, and when you press the gas pedal, the vehicle will make an engine revving noise but not move.
Vehicle Does Not Downshift
Sometimes, after the transmission solenoid goes bad, the vehicle does not downshift when you slow down. Even if you come to a complete stop, the transmission may not shift down. While still in a higher gear, your vehicle will have a harder time accelerating from the stop.
Vehicle Does Not Shift Into the Right Gear
When the vehicle is accelerating, a bad transmission solenoid may not shift up into the proper gear. You can notice this because the car will have a rough ride and not accelerate as quickly as it normally would. Another similar symptom is that the car or truck will shift back and forth between gears while you are not changing speed. Generally you can feel a slight jerk as the vehicle shifts gears.
The easiest symptom to notice is over-shifting. This happens when the solenoid allows the transmission to move more than one gear up or down. Over-shifting often happens when you stop pressing down on the gas pedal. The vehicle will experience a strong jolt as it jerks forward.
Diagnosing the Problem
These symptoms are not the only way to diagnose a bad transmission solenoid. Many times, when you have transmission solenoid problems, your vehicle's "Check Engine" light will turn on. According to Engine-Light-Help.com, many of the codes given by your vehicle's computer will tell specifically what is wrong with your car or truck. Your mechanic or dealer can hook a scanner to your vehicle's computer to retrieve the "Check Engine" light codes.