Transmission Solenoids

►  What is a Transmission Solenoid?
►  What Exactly Do Transmission Solenoids Do?
►  Symptoms of a Failed Solenoid
►  Solenoid Replacement and Cost

What is a Transmission Solenoid?

A transmission solenoid is an electro-mechanical component "valve" used to control the flow of transmission fluid in the transmission.  A typical automatic transmission uses a number of different solenoids for different purposes.  The opening and closing of the solenoids is controlled electronically by the vehicle's Engine Control Module (ECM) or Transmission Control Module (TCM), depending on the vehicle.

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Did you know?    As the name suggests, shift solenoids are used to control gear engagement and gear shifts. It works something like this... When the Engine Control Module (ECM) or Transmission Control Module (TCM) determines it is time to shift to a different gear, (or when the driver manually shifts the transmission), electrical pulses cause the appropriate shift solenoid valve to open. The opening of the solenoid allows transmission fluid to flow to the bands and clutches to effect the desired gear shift. The fluid provides the pressure needed to apply the bands and clutches to engage the gear. 

What Exactly Do Transmission Solenoids Do?

The best way to explain what transmission solenoids do is to describe the different solenoids that are used in an automatic transmission.  The following describes the different solenoids along with their functions.  Also included are problem symptoms, repair information, parts and estimated repair costs.

A modern-day transmission uses solenoids to engage and shift gears, called shift solenoids, which are normally mounted to the transmission valve body.  There is also a Transmission Pressure Control Solenoid and a Torque Converter Clutch Solenoid

Symptoms of a Faulty Shift Solenoid

There primary problem symptoms of a faulty shift solenoid are delayed shifts, no downshifts and erratic shifts.
Delayed Shifts: When the shift solenoids are working properly, shifts occur smoothly and without delay.  A faulty shift solenoid can cause delayed shifts of a few seconds or up to one minute or longer.  During a shift delay no power is delivered to the drive wheels - it's as if the shifter is in neutral.  These shift delays can occur when you first shift the transmission into a gear and when the transmission is shifting between gears.

No Downshift(s): When the shift solenoids are function properly, the transmission automatically downshifts as the vehicle speed slows.  When the vehicle comes to a complete stop the transmission downshifts into first gear.  A faulty shift solenoid can cause the transmission to downshift uncontrollably (in other words at random times) or not downshift at all, even when coming to a complete stop.

Erratic Shifts: A defective shift solenoid can also cause the transmission to shift erratically.  This can be described as shifting into the wrong gear, skipping the intended gear and shifting back and forth between two gears. 


Once it is determined that you have a failed transmission shift solenoid the only repair is to replace the faulty part.  Replacing a transmission shift solenoid can be done by most any auto repair shop, automobile dealership service center or you can do-it-yourself "DIY".

Replacing a transmission shift solenoid or a shift solenoid pack involves dropping the transmission oil pan in order to access the valve body, (where the solenoids/solenoid pack is mounted), locating and replacing the faulty solenoid and then replacing the oil pan using a new pan gasket before refilling the transmission with the correct automatic transmission fluid (ATF).

NOTE: On some transmission models, the solenoids are part of a solenoid pack.  In these instances, you must replace the entire solenoid pack.


The cost for transmission solenoid replacement depends heavily on the type of vehicle you drive.  For example, a single transmission shift solenoid can cost anywhere from $15 to $100.  A solenoid pack, which includes all the solenoids for a particular vehicle/transmission can cost from $65 to several hundred dollars or more.  Where you get the work done, (whether at a local auto repair shop, car dealership or you do-it-yourself), also factors heavily into the cost of repair.  If you replace the solenoid yourself, the parts supplier you purchase the solenoid (or solenoid pack) from will factor into your final cost.

Below are transmission solenoid replacement costs for four different vehicles.  Use this information to give you a rough idea of what your cost might be. 

 Transmission Shift Solenoid - Sample Replacement Cost

REPAIR: Replace shift solenoid
DIY COST: $40 to $65
DIY SAVINGS: $195 to $295

REPAIR: Replace failed solenoid pack
DIY COST: $140 to $160
DIY SAVINGS: $150 to $275 

VEHICLE: 2008 BMW 330i
REPAIR: Replace solenoid pack
DIY COST: $245 to $265
DIY SAVINGS: $390 to $485

REPAIR: Replace shift solenoid
DIY COST: $35 to $45
DIY SAVINGS: $140 to $190  

Normally the transmission fluid that is drained from the pan when replacing a solenoid or solenoid pack is reused.  If you choose to replace this fluid with new fluid the approximate cost is $20 to $50.  ATF costs between $6 and $10 per quart and you will need 3 to 5 quarts.

Fail Safe (or Limp Mode)

A failed transmission solenoid or an open circuit anywhere in the electrical system may cause the transmission to go into Fail Safe (or "limp" mode as it is also called) in order to protect the transmission from internal damage that might be caused by the faulty solenoid or open circuit.  In fail safe/limp mode, the transmission will have limited functionality and will lock in either 2nd. or 3rd. gear.  When the transmission is in fail safe mode, the vehicle should only be drive home or to the repair shop.  Maximum speed while in limp mode is around 30 mph.

Continuing to drive the vehicle with the transmission in fail safe or driving faster than the recommended fail safe speed will cause the transmission to overheat.  Excessive heat build up in an automatic transmission is the #1 cause of catastrophic failure.  So, avoid extended driving when the transmission is in fail safe mode.

A transmission that goes into limp mode will sometimes reset itself when the engine is shut off and restarted.  So, if you find yourself in this predicament, find a safe place to pull off the road and shut the engine off, wait a minute or so and then restart it. 

Diagnostic Trouble Codes P0700 thru P0799

P0700....Transmission Control System (MIL Request)
P0701....Transmission Control System Range/Performance
P0702....Transmission Control System Electrical
P0703....Torque Converter/Brake Switch B Circuit
P0704....Clutch Switch In put Circuit Malfunction
P0705....Transmission Range Sensor Circuit Malfunction (PRNDL Input)
P0706....Transmission Range Sensor Circuit Range/Performance P0707....Transmission Range Sensor Circuit Low Input
P0708....Transmission Range Sensor Circuit High Input
P0709....Transmission Range Sensor Circuit intermittent
P0710....Transmission Fluid Temperature Sensor Circuit
P0711....Transmission Fluid Temperature Sensor Circuit Range/Performance
P0712....Transmission Fluid Temperature Sensor Circuit Low Input P0713....Transmission Fluid Temperature Sensor Circuit High Input P0714....Transmission Fluid Temperature Sensor Circuit Intermittent P0715....Input/Turbine Speed Sensor Circuit
P0716....Input/Turbine Speed Sensor Circuit Range/Performance P0717....Input/Turbine Speed Sensor Circuit No Signal
P0718....Input/Turbine Speed Sensor Circuit Intermittent
P0719....Torque Converter/Brake Switch B Circuit Low
P0720....Output Speed Sensor Circuit
P0721....Output Speed Sensor Circuit Range/Performance
P0722....Output Speed Sensor Circuit No Signal
P0723....Output Speed Sensor Circuit Intermittent
P0724....Torque Converter/Brake Switch B Circuit High
P0725....Engine Speed Input Circuit
P0726....Engine Speed Input Circuit Range/Performance
P0727....Engine Speed Input Circuit No Signal
P0728....Engine Speed Input Circuit Intermittent
P0730....Incorrect Gear Ratio
P0731....Gear 1 Incorrect Ratio
P0732....Gear 2 Incorrect Ratio
P0733....Gear 3 Incorrect Ratio
P0734....Gear 4 Incorrect Ratio
P0735....Gear 5 Incorrect Ratio
P0736....Reverse Incorrect Ratio
P0737....TCM Engine Speed Output Circuit
P0739....TCM Engine Speed Output Circuit Low
P0739....TCM Engine Speed Output Circuit High
P0740....Torque Converter Clutch Circuit
P0741....Torque Converter Clutch Circuit Performance or Stuck Off
P0742....Torque Converter Clutch Circuit Stuck On
P0743....Torque Converter Clutch Circuit Electrical
P0744....Torque Converter Clutch Circuit Intermittent
P0745....Pressure Control Solenoid 'A'
P0746....Pressure Control Solenoid 'A' Performance or Stuck Off
P0747....Pressure Control Solenoid 'A' Stuck On
P0748....Pressure Control Solenoid 'A' Electrical
P0749....Pressure Control Solenoid 'A' Intermittent
P0750....Shift Solenoid 'A'
P0751....Shift Solenoid 'A' Performance or Stuck Off
P0752....Shift Solenoid 'A' Stuck On
P0753....Shift Solenoid 'A' Electrical
P0754....Shift Solenoid 'A' Intermittent
P0765....Shift Solenoid 'B'
P0756....Shift Solenoid 'B' Performance or Stuck Off
P0757....Shift Solenoid 'B' Stuck On
P0758....Shift Solenoid 'B' Electrical
P0759....Shift Solenoid 'B' Intermittent
P0760....Shift Solenoid 'C'
P0761....Shift Solenoid 'C' Performance or Stuck Off
P0762....Shift Solenoid 'C' Stuck On
P0763....Shift Solenoid 'C' Electrical
P0764....Shift Solenoid 'C' Intermittent
P0765....Shift Solenoid 'C'
P0766....Shift Solenoid 'D' Performance or Stuck Off
P0767....Shift Solenoid 'D' Stuck On
P0768....Shift Solenoid 'D' Electrical
P0769....Shift Solenoid 'D' Intermittent
P0770....Shift Solenoid 'E'
P0771....Shift Solenoid 'E' Performance or Stuck Off
P0772....Shift Solenoid 'E' Stuck On
P0773....Shift Solenoid 'E' Electrical
P0774....Shift Solenoid 'E' Intermittent
P0775....Pressure Control Solenoid 'B'
P0776....Pressure Control Solenoid 'B' Performance or Stuck Off
P0777....Pressure Control Solenoid 'B' Stuck On
P0778....Pressure Control Solenoid 'B' Electrical
P0779....Pressure Control Solenoid 'B' Intermittent
P0781....1-2 Shift
P0782....2-3 Shift
P0783....3-4 Shift
P0784....4-5 Shift
P0785....Shift/Timing Solenoid
P0786....Shift/Timing Solenoid Range/Performance
P0787....Shift/Timing Solenoid Low
P0788....Shift/Timing Solenoid High
P0789....Shift/Timing Solenoid Intermittent
P0790....Normal/Performance Switch Circuit
P0791....Intermediate Shaft Speed Sensor Circuit
P0792....Intermediate Shaft Speed Sensor Circuit Range/Performance
P0793....Intermediate Shaft Speed Sensor Circuit No Signal
P0794....Intermediate Shaft Speed Sensor Circuit Intermittent
P0795....Pressure Control Solenoid 'C'
P0796....Pressure Control Solenoid 'C' Performance or Stuck off
P0797....Pressure Control Solenoid 'C' Stuck On
P0798....Pressure Control Solenoid 'C' Electrical
P0799....Pressure Control Solenoid 'C' Intermittent

Diagnosing a failed transmission solenoid with Check Engine Light

A failed transmission solenoid will normally set a diagnostic trouble code (DTC), which will cause the check engine light to illuminate.  In these instances, an OBD-II scan of your vehicle's computer will provide information pointing to the faulty solenoid.  The DTC information (or explanation) will almost always include a statement indicating that the problem may be an open circuit in the transmission electrical system.  Therefore, you should always test the solenoid to verify its condition before replacing it. DTC codes specific to transmissions and solenoids are listed below.

Diagnosing any Transmission Problem with NO Check Engine Light

A correct diagnoses of a transmission problem when there is no check engine light is best accomplished with a professional transmission scan.  This type of scan will necessitate a visit to a transmission shop or car dealership.  A professional transmission scan can cost between $60 and $125.  This charge is normally referred to as a diagnostics fee.  It is standard procedure for the shop making the repair to waive the diagnostics fee. 

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