How to check if the speed sensor is good?
HOW IT WORKS The Vehicle Speed Sensor (VSS) is a variable reluctance sensor that generates a sine wave type waveform with a frequency that is proportional to the speed of the vehicle.It has a gear on it that meshes into either the transmission/transaxle or the differential (depending on the vehicle.Probably in the differential of a FORD RANGER) When the vehicle is moving slowly, the sensor produces a low frequency signal. As the vehicle speed increases, the sensor produces a higher frequency signal. This signal is sent to the PCM and is converted into a vehicle speed value, stored in RAM memory. The PCM utilizes this value to aid in controlling torque converter lock-up/transmission/transaxle shift points, control fuel injection, ignition timing and , coolant fan control, vehicle speed control, air/fuel ratio and ignition timing. MY OBERVATIONS AND COMMENTS It works like a little alternator of sorts, or probably more correctly like the rotor and pick-up in an electronic ignition system. When it is spinning with the transmission or differential gears it generates small electric pulses which are sent to the engine control computer. The faster it spins the higher the frequency. I have tested some of mine two different ways. One way is to remove it from the tailshaft of the transmission or the differential housing (depends on vehicle)and hook the two leads to a volt meter on the AC scale or if you have a digital meter with a frequency scale you can use that too. This will measure the frequency in HERTZ (Hz.),meaning cycles per second. Spin the little gear(probably nylon)as fast as you can by hand (drag your hand /arm across it real fast like you were winding up a toy car or top)and watch the voltmeter for a reading. If you get a reading ( a few volts or Hz.) it's probably still functioning. You could also turn the gear with a variable speed drill.Keep it slow to be on the safe side.I'm guessing under 1000 RPM (most variables top out at 1250rpm for 1/2" and 2250rpm for 3/8"). If it won't go in the drill chuck (some gears have a little nub on the end you can grab),then wrap the gear with some tape and press the gear onto the side of the chuck,sort of like a bicycle generator on a bike tire.The tape will protect the little gear and help increase the friction between the two so it spins easily. Another way is to leave the sensor in place, jack up the vehicle,drive wheels off the ground and turn the drive wheels by hand with your test apparatus hooked up to the leads on the sensor for similar results. The main thing is that you get varied voltages/frequencies at different speeds.If you get nothing it's busted. I DO NOT recommend that you run the vehicle while it is jacked up. Spinning the wheels by hand will tell you all you need to know. I don't know the exact voltage or frequency you should get because it's all based on how they designed the sensor, how they calibrated the computer,the gear ratios of the sensor to the transmission or differential, and how fast you spin it. If you get different voltage and/or frequency readings at different speeds,it's probably good. The resistance across the two terminals of the sensor for a 1993 FORD RANGER is supposed to be 190 to 250 OHMS. If the sensor checks out good ,you may have a problem in the connectors or wiring .Often a close visual inspection of the connectors and wiring will reveal the problem before you have to break out a meter and run continuity checks Also check out the condition of the gear on the sensor and make sure that it is not chewed up and is properly fixed to the shaft of the sensor and not spinning loose on the shaft. I tried the first method with the drill with a 1990 NISSAN speed sensor and at approx 1000 RPM I got about 7 volts AC and 270 Hz. Also, the measured resistance across the two terminals of the sensor was 258 OHMS.
What to check on a 2004 HD Road King when the turn indicators nor speedometer not check engine light do not work?
do you mean, needle bounce all around the speedometer gauge face ? like a windshield wiper ? check / replace speed sensor on your transmission check instrumentation for short or grounded wire/circuit. check the guage for defects, but most probably it is the speed sensor... worst is the ECU,, speed sensor is connected to the ECU of a vehicle;
Locate the vehicle speed sensor of the vehicle mounted to the rear section of the transmission. Disconnect the electrical connector from the sensor. Remove the retaining bolt from the sensor mounting at the transmission, then pull the sensor out of the transmission. Place the sensor on a flat surface, then slowly turn the sensor gear by hand. Use the voltage meter to check for the pulsing AC voltage from 0 to 0.5 volts. If there…
How do you make the speed sensor work as you changed transmissions from a 1999 to a 1996 Chevrolet Camaro 5 speed?
To check if a speed sensor is bad. Pull the sensor and connect your ohm (resistance) meter probes to the two terminals of the speed sensor. There needs to be 7 or more pulses of zero resistance, and the resistance between needs to be infinite. There are 2 speed sensors, an input and output. I had this happen once, and to put it real simply, your speedometer won't work anymore.
Drive on a freeway or highway where there's a speedometer check point. Set your odometer to zero, drive the exact speed limit (try to use cruise control), and after the speedometer check point is over (5 miles), you will be able to determine if your speedometer is working correctly based on the miles driven according to your odometer and the end of the checkpoint.
A sensor has failed, and is reporting the wrong value to the transmission controller. Old transmissions: Probably the vacuum modulator or throttle position sensor. Also check the fluid level. New Transmissions: Output speed sensor, turbine speed sensor, throttle-position sensor, fluid pressure sensor, and sensors on the engine.
do you mean your car won't display your car speed ? is that what you mean ? check the speedometer cable on your car. check the speed sensor located at the end of the speedometer cable. check the plastic gear inserted on the transmission at the end the speedometer cable. get a qualified technician who can work on your car.. it may require the instrument panel (gauges assy) be remove to unplug the other end…
Your 1998 chev cavalier shows a obd-ii trouble code po502 vss circuit low input what can you troubleshoot to find out what is wrong?
you have either a bad speed sensor (check engine light on?) or a short in the printed panel and amp/ voltage reg. on the back of the speedo head. no check engine light on replace/ rebuild speedo head there are speedo shops. if light is on replace speed sensor as the OBD system uses this sensor to. clear codes and happy driving Johnie
What do you do when you were driving a Chevy Cavalier and it all of a sudden acts like it is neutral when it isn't?
Check the transmission fluid first. If the fluid is fine, check the Speed Control Sensor. This happened to me yesterday, and computer diognostics showed it to be the Speed Control Sensor had gone bad. Fluid is a good place to start. Make sure you change it IAW your owners manual or service professional. If it is within correct range get the fly wheel checked if a manual, if automatic it still may be the flywheel…