low tranmission fluid symptoms

Transmission Shift Solenoid: Functions & Symptoms

In Transmission by Josh S2 Comments

Modern transmissions use a lot of electronics as you may know. If one of those hundreds of electric parts fails, the whole transmission could fail.

What’s happening when an electric part gets defective, is that the engine control unit/transmission control unit feels it and put the engine and transmission into limp mode.A very common part in the transmission that could fail, is one of the shift solenoids. In this guide, I will write about, what is a shift solenoid? And how to fix it the easiest and cheapest way?

What is a transmission shift solenoid?

transmission shift solenoid

The transmission shift solenoids job is as it sounds, shift gears for you. The transmission control unit is getting information from the engine and the vehicle speed sensors and other parameters. It uses this information to know when it’s time to shift. When it’s time to shift, the transmission control unit sends out power or ground to the required shift solenoid and it makes the solenoid to open and let the transmission oil flow into the valve body.

The shift solenoids are spring loaded with a coil inside. Depending on the car, but it normally has 12 volts to it all the time and gives ground to it when it’s time to open.

As we now know that the solenoid requires 12 volts and one ground wire to open, we can figure out what is happening when one of those are missing. The TCM (Transmission control unit) puts out a trouble code on “Open Circuit”. The shift solenoid could also have an internal fault.

Symptoms of a bad transmission shift solenoid

The most common symptoms of a faulty shift solenoid are:

How to fix/diagnose a shift solenoid problem?

ask a mechanicFirst, we have to figure out if it’s a wire, shift solenoid, TCM or mechanical fault. We have to read the DTC code carefully and understand what it is saying. If it is saying that it’s stuck or electrical problem it is most likely a wiring or shift solenoid problem.

A lot of the shift solenoid codes could be solved by trying to make a transmission fluid replacement or a transmission flush.

Common Shift solenoid DTC Codes

P0750 – Shift Solenoid A
P0752 – Shift Solenoid A Stuck On
P0753 – Trans 3-4 Shift Sol/Trans Relay Circuits
P0754 – Shift Solenoid A Interm
P0755 – Shift Solenoid B
P0756 – AW4 Shift Sol B (2-3) Functional Failure
P0757 – Shift Solenoid B Stuck On
P0758 – Shift Solenoid B Electrical
P0759 – Shift Solenoid B Interm
P0760 –  Shift Solenoid C
P0761 – Shift Solenoid C Perf or Stuck Off
P0762 – Shift Solenoid C Stuck On
P0763 – Shift Solenoid C Electrical
P0764 – Shift Solenoid C Interm
P0765 – Shift Solenoid D
P0766 – Shift Solenoid D Perf or Stuck Off
P0767 – Shift Solenoid D Stuck On
P0768 – Shift Solenoid D Electrical
P0769 – Shift Solenoid D Interm
P0770 – Shift Solenoid E
P0771 – Shift Solenoid E Perf or Stuck Off
P0772 – Shift Solenoid E Stuck On
P0773 – Shift Solenoid E Electrical
P0774 – Shift Solenoid E Interm

 

If you get an electrical or stuck code, the easiest way to check this is with an OBD2 reader that can do “output test”. If you do not have an OBD2 reader with this function at home, you can lend one or check out our article OBD2 Scanner Reviews.

  1. Find a transmission wiring diagram for the required transmission.
  2. Find out which pins are going to the code that you get a fault code on.
  3. Loosen the transmission wiring plug on the transmission
  4. Use the OBD2 scanner and start the output of the required shift solenoid
  5. Measure that you get both 12 volts and ground to the shift solenoid with the DTC code.

If you do not get both 12 volts and ground, you may have a wiring problem or a faulty TCM ( Transmission control unit ).

If you get 12 volts and ground and the shift solenoid trouble code keeps coming back after you erased it, you do probably have a faulty shift solenoid.

Transmission Shift Solenoid Troubleshooting

ProblemSymptomsCausesSolutions
Transmission shift solenoid problemShifting delays

Skip / Jump over some gears

Stuck in gears

Downshift / Upshift problems

Check Engine light

Limp mode
Faulty Shift Solenoid

Low transmission fluid

Bad electrical connections on transmission

Faulty wirings to shift solenoid

Faulty TCM(Transmission control unit)
Replace Shift Solenoid(If possible)

Check transmission fluid level

Clean connectors on transmission

Repair wirings between shift solenoid and TCM

Replace TCM

How to repair a transmission shift solenoid?

transmission valve body

If the shift solenoid itself has an internal error, the best way is to replace the solenoid. As I mentioned before, a transmission fluid replacement or a transmission flush can solve some shift solenoid trouble codes if you want to try it out first.

To replace a shift solenoid, you have to remove the transmission fluid pan to reach the faulty solenoid. It is located in the valve body.

Warning: In some vehicles, you can’t replace just one solenoid, you have to replace the whole solenoid pack. Always check this with your dealer before you are starting to remove the transmission pan.

How much is the cost of a shift solenoid replacement?

The cost of a shift solenoid replacement is depending a lot on what car model you have. As I mentioned before, in some cars you can’t replace just one solenoid. You have to replace the whole solenoid pack and it could be expensive. When you are replacing a shift solenoid or shift solenoid pack, you are also usually replacing the transmission fluid.

Single shift solenoid replacement: ~50 – 150$

Shift solenoid pack replacement: ~200 – 500$

Prices can vary a lot depending on if the workshop is using original parts and what transmission fluid they are using.

 

Summary

Some shift solenoid replacements can be solved by replacing the transmission fluid or do a transmission flush. If you can’t replace a single solenoid it could be worth a try to replace transmission fluid. You should always make sure that there is not a wiring problem between the transmission control unit and the solenoid.

In some cars, you have to replace the whole solenoid pack. Call your authorized dealer before making any repairs to your vehicle.
If you want more help about how to troubleshoot your transmission, you can check out our Transmission problems repair guide.

 

If you do still have some questions about the shift solenoid that you want answers for. Comment down below and I will answer them as soon as possible. If you have other car questions you can go to our homepage and ask a mechanic for free.

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Comments

  1. Hi, i have a solenoid b fault on my 2004 Ford focus.
    Would replacing the gearbox fix this issue?

    Thank you, Chrissie

  2. Author

    @Chrissie
    In a lot of automatic transmissions, you can replace the solenoid or so-called the whole solenoid pack. It’s recommended to measure the solenoid with a multimeter from the transmission control unit connector to check if there are any open circuits, take help of a wiring diagram. If you see an open circuit, measure the same wirings on the transmission, if this line is okay, check the wirings between transmission control unit and the transmission. If you do not know a lot of car electronics, I can recommend to let a good mechanic measure it before replacement of the solenoid pack or transmission.

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