A vehicle speed sensor or engine speed sensor is the device that takes and sends data to your car's computer system in regards to what speed your engine's spinning rate is going.
The sensor senses this by noting the rate the crankshaft is spinning. You can experience difficulties with your vehicle if your sensor has been compromised. This includes the check engine light coming on and demanding your attention, inactive cruise control, and harsh or improper shifting when push comes to shove.
Incidentally, the symptoms of a bad transmission speed sensor are the same as issues with a faulty coil pack or a bad throttle position sensor. Consult with your mechanic for more details.
How to Look for Problems in the Vehicle Speed Sensor
- Improper or Harsh Shifting: When the sensor for transmission or engine speed sensor malfunction, this results in poor control with shifting gears on the part of the Powertrain Control Module or PCM. You therefore end up with higher revs before you shift gears or leading late transmission overdrive. Your vehicle is also unable to go to top gear. Harsh shifting is dangerous because it damages your vehicle's internal components such as the mechanical gears, hydraulic lines, and valve bodies.
- Inactive Cruise Control and Speedometer Issues: Your cruise control may also become inactive to safeguard your vehicle from the malfunctioning speed sensor. This is because this car part doesn't only control the speed of the input and output shaft. It also monitors the cruise control. Without it, an error code will be sent to the ECU or Engine Control Unit. This is a failsafe shutdown essentially. In turn your speedometer can also shut down or work frantically in light with your compromised sensor.
- Blinking Check Engine Light Whenever You Accelerate: Another symptom that it's your engine speed sensor specifically that's malfunctioning is your check engine light. If it only blinks intermittently or sporadically every time you accelerate, then perhaps it's a speed sensor problem. Your overdrive light might also blink or go on and off as well. It's also important to check what error the check engine light is alerting you to. The diagnostic trouble code provided by the PCM should refer to an error relating to the sensor in question.
- Troubleshooting and Repairing the Engine Speed Sensor: Your mechanic might have to check the problem with your speed sensor by running a complete computer diagnostic test. The car computer was invented specifically to make it easier for the repairman to pinpoint what's wrong with your car without having to test different parts manually. Just alert the auto repair shop about the other symptoms that should help them eliminate any other potential issues with your vehicle. From there, they can quote you a price for parts and labor.