Bad Transmission Solenoid Symptoms: Diagnosis and Fixing

Before concluding that the negative signs of your vehicle shifting are bad transmission solenoid symptoms, there are some important things to look out for.

Automatic vehicles don’t make shifts by chance. Some vital components function and interact together to make a proper automatic gear shifting, and transmission solenoid is one.

So, unless your vehicle has a faulty transmission control solenoid, you may never hear of this vital component of the vehicle.

Before we dive into how you will know when this part of your vehicle is getting bad or requires the attention of a mechanic, let’s get a clear understanding of what a solenoid is and its function in a vehicle.

what happens when a transmission solenoid goes bad

What does a transmission control solenoid do?

A transmission control solenoid is an electromechanical component of a vehicle. It’s a valve that determines and regulates fluid flow in a vehicle transmission.

This component functions or responds to voltage or electro signals from a transmission control module, another component of the vehicle that evaluates signals from the engine speed sensors. It is also steel-made and cylindrical.

Similar to the manual transmission which depends on the clutch to control gear shifting, the automatic transmission uses solenoids to execute the same functions in a vehicle. To make proper gear shifting in automatic vehicles, solenoids have to supply the right volume of fluid through the system.

Transmission solenoids are in charge of regulating the flow and pressure of the fluid. It opens and closes to either take in more or prevent any more fluid from passing through to make shifts.

This is no doubt a vital component that keeps your vehicle moving. However, there are certain signs you’d see when this component starts failing. Here’s what happens when a transmission solenoid goes bad.

Bad transmission solenoid symptoms

Unusual gear shifts

This is one of the most prevalent shifting solenoid problems. When this part of your vehicle becomes faulty, you can experience unpredictable or unexpected gear shifting.

For instance, when you’re driving with a specific gear and the vehicle suddenly makes an unexpected shift to a higher gear, this can be dangerous for the driver and the vehicle as well.

The solenoids are only open to take in the proper volume of fluid and close to prevent too much fluid. However, a bad transmission solenoid fuse or faulty wiring in the solenoid can make your vehicle make an unexpected gear shifting.

This problem manifests either. This means you may experience an unexpected shifting to a higher gear, thereby increasing the vehicle speed. The gear may also shift to a lower one when you’re trying to accelerate or get past a slower vehicle.

You must ask for the help of a transmission expert as soon as you start seeing symptoms like this. Ignoring it will only result in more catastrophic and expensive problems for the owner and the vehicle itself.

Delayed shifting

Pressure is what propels automatic transmission. This means that the pressure within is what controls a vehicle gear shifting, and this pressure is controlled by the solenoid.

Unfortunately, solenoids don’t last forever. After several years of consistent use, they become old and start to fail. This is when you start noticing problems with the vehicle transmission shifting, especially when it takes longer than usual.

For instance, you may notice an unusually long gap in transmission shifting response. If your vehicle is taking longer than the normal time to shift, it’s likely a problem with the solenoid.

Sometimes, dirty fluids in the solenoid can cause it to close or stay open. This in turn makes your vehicle transmission function abnormally or take longer than expected. Therefore, bad transmission relay symptoms like this should be addressed.

Unable to downshift

Sometimes, a problem with a vehicle solenoid may not affect acceleration and gear upshifting, but then you will experience difficulty in downshifting – either slow downshifting or vehicle not downshifting at all.

This is what happens when your vehicle’s transmission solenoid becomes faulty and becomes stuck open. There could be several reasons for this.

First, it can be a problem with the internal wiring of the solenoid. Bad wiring within the solenoid may not transmit electrical signals to the solenoid, causing it to stay open, take in more fluids and pressure, and be unable to downshift.

Another reason is simply a damaged solenoid. When the solenoid itself is damaged, you will experience downshifting difficulties like this. Your vehicle may also be unresponsiveness to downshifting due to the intake of dirty fluid.

This means that too much influx of dirty or contaminated fluid can weaken the solenoid response to signals from the transmission control module, thereby causing difficulty in downshifting.

Check the engine light signal.

When the check engine light comes on, it means there’s a problem with your engine that requires attention; therefore, it shouldn’t be ignored. Most times when this light is on, vehicles transmission often switches to safe mode, which makes it more difficult for you to drive.

In cases like this, you’d be limited to certain gears and power, making it obvious that there’s a problem with the vehicle engine which needs urgent attention. When this happens, don’t hesitate to call for the help of a transmission expert or a mechanic.

Bad transmission solenoid symptoms

Diagnosis and fixing Bad transmission solenoid

To diagnose the problem of the transmission solenoid, we have to find out what is causing the problem and which part of the engine it’s coming from, as it may be a problem with the internal wiring, transmission control module, or some other mechanical fault.

You may want to call for the help of a transmission expert, or you can decide to do the transmission shift solenoid test yourself. However, to do the latter, you’ll need to research trouble codes so that you can understand the exact fault of the vehicle.

In case the trouble code shows that there’s an electrical fault, it’s likely a problem with the wiring. Most trouble codes related to solenoid problems can be easily resolved by changing the transmission fluid or flushing it completely.

Whether you decide to replace the solenoid fluid or do a transmission flush, it’s always worth it and not expensive.

A scanner is important for transmission solenoid troubleshooting or diagnosis. To do this, you need to find a transmission diagram that shows the wiring pattern.

Next, you’ll need to look for the pins that go to the faulty solenoid. Remove the transmission plug that’s on the transmission. Then use the scanner to detect the faulty shift solenoid. The trouble codes from the transmission shift solenoid test will help you understand the problem.


Can you drive with a bad transmission solenoid?

Yes, you can drive a vehicle with a bad transmission solenoid. Nevertheless, you should keep in mind that the problem may escalate into an expensive repair if not taken care of as soon as possible.

Also, since solenoids are in charge of controlling gear shifting and vehicle acceleration, the driver will experience difficulty as he drives without fixing the solenoid fault.

Can you start a car with a bad solenoid?

Unless your vehicle has a bad starter solenoid, you can still start your car. Faulty starter solenoids affect a vehicle by causing it to start on its own without the driver turning the key to start the vehicle.

Either your vehicle is having a problem with the starter solenoid or the transmission solenoid, you should address the problem without delay.

How much does it cost to replace the shift solenoid?

To replace one shift solenoid can cost between $100 to $350, making the pack of a shift solenoid cost about $400 to 700 dollars, as well as the cost for labor, the transmission fluid, parts, and filter.

You should also know that transmission solenoid repair costs may vary depending on the model of the transmission as well as the vehicle model. Some vehicles only permit the replacement of the whole pack instead of one or two faulty solenoids.

Sometimes, you may have to replace the complete body of the valve, which may be expensive. Nevertheless, always change the filter and transmission fluid whenever you replace a solenoid, the body of the valve, or the complete pack.

How long does it take to change a transmission solenoid?

Changing a transmission solenoid takes about 2 to 4 hours, which makes it easier to calculate the labor cost for fixing this part of your vehicle. So far, you’re paying per hour; you can deduce what the total cost will be by adding the cost of hours it’ll take to the cost of the part replacement.

Will a bad shift solenoid always throw a code?

When you diagnose your vehicle for solenoid problems using a scanner, you’ll always see a trouble code. This trouble code may persist even after troubleshooting the engine, and this means the fault is yet to be fixed.

If you tried troubleshooting it yourself and the problem persists, you should call a mechanic or a transmission expert to examine the trouble code and look into the vehicle.

Final Words

Bad transmission solenoid symptoms manifest in different ways. As mentioned, you may experience difficulty in downshifting, as well as unusual gear shifting either upwards or downwards.

Your gear may also get stuck if your vehicle solenoid gets faulty. When you start seeing these signs, it means your vehicle solenoid requires attention, and you shouldn’t hesitate to fix the problem.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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