How to Test a Transmission Speed Sensor

It provides vital information to your car’s powertrain computer; make sure it’s on point.

byMay 15, 2020 12:00 PM
How to Test a Transmission Speed Sensor
Share

The Drive and its partners may earn a commission if you purchase a product through one of our links. Read more.

So your car’s transmission is acting up or throwing a heart-stopping fault code and you want to find out if the speed sensors are causing it? Fabulous. 

Your car’s transmission speed sensors are vital to its powertrain operation. Most modern cars have two transmission speed sensors, one at the input shaft and another at the output shaft. These sensors work in tandem to send the powertrain control module (i.e., the computer that manages the engine and transmission) the speed difference between the engine crankshaft and the transmission output shaft, and thus, the gear ratio. That data, along with data from other sensors around the car, is used to set shift points, adjust engine calibrations, and even manage cruise control. If those sensors aren’t working properly, the transmission may shift roughly or sluggishly, cruise control may not work, or the speedometer may malfunction.

Diagnosing a faulty transmission speed sensor is pretty straightforward, as is replacing it, but to diagnose a problem fully, you’ll need to be comfortable using a multimeter to check voltage. If not, take your car to a qualified mechanic for a proper once-over. The Drive’s crack How-To team is here to help you diagnose and fix your transmission speed sensor issues, and get back on the road.

Basics

Estimated Time Needed: Half-hour

Skill Level: Intermediate

Vehicle System: Transmission

Depositphotos

Safety

Working on your car can be dirty, especially when you’re working with surfaces you’ve never bothered to clean before. It can also be dangerous as liquids can be scaldingly hot and tires could fall on your toes. So here’s what you’ll need to ensure you keep your jeans, shirt, and skin spotless, and your bones fully intact.

Organizing your tools and gear so everything is easily reachable will save precious minutes waiting for your handy-dandy child or four-legged helper to bring you the sandpaper or blowtorch. (You won't need a blowtorch for this job. Please don’t have your kid hand you a blowtorch—Ed.)

You’ll also need a flat workspace, such as a garage floor, driveway, or street parking. Check your local laws to make sure you’re not violating any codes when using the street.

Depositphotos

Everything You’ll Need

We’re not psychic, nor are we snooping through your toolbox or garage, so here’s what you’ll need to get the job done.  

Tool List

Parts List

  • New transmission speed sensors (if applicable)
Depositphotos

Here’s How to Test Your Transmission Speed Sensors

Let’s do this!

Testing Transmission Speed Sensors

  1. Using an OBD2 scanner, check to see if there are any error codes related to the transmission speed sensor.
  2. If there are, there’s your problem. The part will need to be replaced.
  3. If there aren’t any codes, or if your car is from the Regan years, you’ll need to physically test the sensor.
  4. For better clearance, lift up the front end of your vehicle.
  5. Locate the transmission speed sensors, they’ll be near the front and rear of the transmission housing. Consult the repair manual for your car.
  6. Place bucket or oil drain pan underneath the sensor, there will be some oil that drains out.
  7. Disconnect the sensor from the housing on the transmission, as indicated in the repair manual for your car.
  8. Disconnect the sensor’s wire coupling.
  9. Turn the key to the ignition on, but engine off, position (one key click past Accessory)
  10. Using the multimeter’s voltmeter connect the probes to the ground and reference wires in the connector.
  11. If no voltage is received, the sensor is faulty.  
  12. If voltage is received, you may need to have the car diagnosed by a qualified tech.

Replacing Your Transmission Speed Sensors 

  1. Having found the sensor or sensors to be faulty, remove the connector between the sensor and the vehicle’s wiring.
  2. Using the proper socket, remove the faulty sensor.
  3. Connect the new sensor to the vehicle’s wiring.
  4. Install the new sensor.
  5. Lower your car.
  6. Start the engine.
  7. Take a test drive.
  8. Check to make sure the transmission shifts properly.
  9. Check to make sure the cruise control works properly.
  10. Wait to see if the check engine light goes off.
  11. If everything is a-ok, you’re golden. 

Congrats, you did it!

Depositphotos

Tips From a Pro

Here are our top pro tips to help you diagnose and fix your transmission speed sensor.

  • If your transmission becomes bucking-broncoesque, pull over. You’re likely to cause serious damage to a number of parts if you continue.
  • A fluctuating speedometer may be a sign of a faulty transmission sensor.
  • If you have a truck or SUV with enough ground clearance, you won’t need to jack up your car. 

Life Hacks

Since you may not have access to the right tools, we also compiled a list of our best hacks to make your life easier and drain your pocket less.

  • If you don’t have an OBD2 scanner handy, your local auto parts shop will loan you one.

How Often Do You Need To Test Your Transmission Speed Sensor?

Automakers build these sensors with a long lifecycle, the only reason you’d need to test or change the transmission speed sensor would be because it began to malfunction again. 

Featured Products

Ancel AD310

Power Probe IV with Case

Gerber Dime Multitool

Got a question? Got a pro tip? Send us a note: guidesandgear@thedrive.com

Other ‘Auto Repair and Maintenance’ Reviews You Might Like:
Shock AbsorbersAuto Repair and MaintenanceAuto Repair and MaintenanceGet Ready for Fall and Winter Driving with Great Deals for Your Car, Truck, Motorcycle, and GarageAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceLate Summer Means Big Savings on Cars—plus Auto Parts, Accessories, and Tools at Walmart, Amazon, and Moremotorcycle dealsAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceHGV Mini Tire Inflator Digital Portable Air CompressorAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceAuto Repair and MaintenanceWorkpro’s 39-Piece Tool SetAuto Repair and MaintenanceHow To Change Your Motorcycle's Oil100+ of the Best Deals for Auto Enthusiasts on Amazon Prime Day 2021, Day TwoThe Best Automotive Amazon Prime Day Deals: Live NowDeals, Deals, Deals! Big Savings on Gear, Tools, and More from Amazon, Walmart, eBay and Best BuyTime is Running Out for Father's Day DealsWill the BRIDJIT Three-Piece Expandable Curb Ramp Keep Our Bumpers Safe?How Garage Air CompressorsOne of Our Favorite Torque Wrenches is Nearly 40% Off Right Now and We're Annoyed We Already Own ItMilwaukee’s M18 Fuel Half-Inch High Torque Impact Wrench Is for When You Need the Power of Mjölnir: ReviewHow a Portable Tire Inflator WorksThe Drive's Daily Deals Roundup: The Best Auto Gear On Sale This Week from Walmart, Lowe's, Amazon, and MoreThe Ultimate Father’s Day Tools Gift Guide: Walmart, Amazon, Northern Tool, Advance Auto, and MoreTekton’s 30-Piece Hex Key Set Might Be the Most Dynamic Set Ever — MaybeFix Your Car Like a Professional with GearWrench's Torque WrenchCheck Out These Fantastic Father’s Day Gifts from Advance Auto PartsNow's the Time to Get Great Deals on Summer Driving Gear and Gifts for Father's Day Eklind's Hex-L Key Set Unlocks All ConcernsYes, a Tekton Torque Wrench Can Be Both Cheap and GoodDaily Deals: Hot Bargains on Car Tools, Garage Gear, and Tech from Amazon, Walmart, Home Depot, and MoreStockton Roadside Tool Kit: An Undeniable Deal on the Portable Tool Kit Every Motorcyclist Should Ride WithHow To Install New Handlebars on Your MotorcycleHow To Turn a Motorcycle Using Its KickstandWe Gave This Craftsman 1/2-Inch SAE Torque Wrench the Beans And It Held UpDoes RAM Mounts’ X-Grip Motorcycle Phone Mount Live Up to the Hype?We Ramp Up the PSI While Testing the Jaco SmartPro 2.0 AC/DC Digital Tire InflatorWe Go Portable With the Ryobi P737 18-Volt One+ Cordless Power InflatorGetting Our PSI On With the Husky Electric Air Tire Pump 120V InflatorHow To Fix Tears in Vinyl SeatsStock Your Garage With Harbor Freight's Memorial Day Tool SaleHow to Tune a CarburetorHow To Shoot and Adjust Ignition TimingHow To Dispose Of Old GasTrailer MaintenanceWhat Is an Impact DriverHow To Build the Perfect Mechanic’s GarageGarage LightingBad Fuel Pump SymptomsHow To Check for Vacuum LeaksHow To Test a Spark PlugHow to Adjust a CarburetorThrottle Position Sensor SymptomsCv Axle ReplacementHow Much Does Window Tinting CostWhy Your Ball Joint Failed and How to Replace ItHow to Bleed Brakes by YourselfTie Rod EndWhat is the Lifespan of An AlternatorHow To Remove Jeep DoorsHow To Test a Car BatteryHow To Install Car SpeakerPower Steering Pump NoiseWheel Repair10 Steps to Get Your Garage Ready for WinterSigns of a Bad Water PumpHigh Oil PressureWhat Is a Purge ValveHow To Use Jack StandsBrake GrindingHow To Winterize Your CarIntake Manifold GasketRepairing a Driveway? The Right Solution for Every SurfaceHere Are The Tools That Readers Of The Drive Can't Live WithoutTransmission RebuildExhaust LeaksStripped BoltBrake Fluid LeakEVAP Leakcar shocksHybrid Battery ReplacementDriving on a Flat TireReplace HeadlightCar Vibrates When AcceleratingWhen To Change Spark PlugsClogged Fuel FilterWhite Smoke From ExhaustWhat is a Smog Check?Timing Belt CostWhat Causes a Blown Head GasketCar Won't StartWheel Alignment CostCar OverheatingTire BalancingTune UpAntifreeze LeakHow to Dispose of AntifreezeBrake Pad Replacement CostCar Radio RepairSerpentine BeltABS Light OnHow To Disconnect A Car BatteryHow To Clean A Catalytic ConverterTransmission SlippingCar MaintenanceSymptoms Of A Bad AlternatorWindshield RepairGarage Door RepairHead Gasket RepairTPMS LightCar Heater Not WorkingCar Dent RepairCar AC RepairKey Stuck In IgnitionEngine Block HeaterCar Shakes When BrakingHow To Gap A Spark PlugHow Often To Change Synthetic OilCar Cranks But Wont StartHow To Change Spark PlugsHow To Test A RelayHow To Use A Torque WrenchCar Won't Start & You Hear a Clicking NoiseHow To Reset Check Engine LightHow To Check Power Steering FluidWhat Does A Bad Starter Sound LikeTransmission Fluid ChangeCar Windshield RepairHow To Clean a Motorcycle ChainHow To Replace Brake PadsHow To Lubricate Garage DoorHow To Recharge Car ACHow Often To Change Oil?How Often Should You Rotate Tires?How To Start a Car That Has Been Sitting For 1 Year?How To Clean Battery TerminalsHow to Mix Auto PaintHow To Reupholster Car SeatsHow To Remove Scratches From a CarHow To Change Your Fuel FilterHow To Test Your Oil PressureHow to Clean Fuel InjectorsHow to Fix a Temperature GuageHow to Remove Rust From Your CarHow To Lift a CarHow to Rotate Car TiresA DIY Air Conditioner Recharge Can Cool Your Jets