Vehicle speed sensor location diagram

If there are some engine speed sensor problems , it may lead to other difficulties in your car. The symptoms of a bad transmission speed sensor are same to some other engine problems, like bad throttle position sensor or faulty coil pack. This may cause transmission revs higher before shifting gear or leading late transmission overdrive and inability to go into that top gear.

VSS - Vehicle Speed Sensor Testing - FreeAutoMechanic

Harsh shifting may damage internal components such as valve bodies, hydraulic lines, and even mechanical gears in some cases. If your car has some engine speed sensor problems, the Powertrain Control Module PCM will set a diagnostic trouble code and illuminate the Check Engine Light on the vehicle dashboard. Then the check engine light comes on sporadically and intermittently when accelerating.

If you notice any of the above-mentioned symptoms, you should have your car checked at a nearby auto repair shop. While the problems may be transmission related, run a complete computer diagnostic test at a repair shop, instead of directly taking your car to a specialty shop. Finding cheap used cars from reliable Japanese sellers? Tsukasa Azuma is an awesome car blogger of Car From Japan. He owns a car repair shop at downtown Osaka, and he put all that experience to good use in his sharing posts.

Login with Google. Likes Followers Followers. Import used cars directly from Japan. Many of the subsystems in a rail vehicle, such as a locomotive or multiple unit , depend on a reliable and precise rotary speed signal, in some cases as a measure of the speed or changes in the speed. This applies in particular to traction control , but also to wheel slide protection , registration, train control, door control and so on. These tasks are performed by a number of rotary speed sensors that may be found in various parts of the vehicle.

Speed sensor failures are frequent, and are mainly due to the extremely harsh operating conditions encountered in rail vehicles. Although rail vehicles occasionally do use drives without sensors, most need a rotary speed sensor for their regulator system. The most common type is a two-channel sensor that scans a toothed wheel on the motor shaft or gearbox which may be dedicated to this purpose or may be already present in the drive system.

Speed Sensor

The form of the teeth is of secondary importance; target wheels with involute or rectangular toothing can be scanned. Depending on the diameter and teeth of the wheel it is possible to get between 60 and pulses per revolution, which is sufficient for drives of lower and medium traction performance. This type of sensor normally consists of two hall effect sensors , a rare earth magnet and appropriate evaluation electronics.

The field of the magnet is modulated by the passing target teeth. This modulation is registered by the Hall sensors, converted by a comparator stage to a square wave signal and amplified in a driver stage. Unfortunately, the Hall effect varies greatly with temperature. This also very much reduces the maximum permissible air gap between the sensor and the target wheel. In this case the maximum possible air gap is only 0.

For the design engineer, the visible air gap that the sensor ends up with is primarily the result of the specific machine design, but is subject to whatever constraints are needed to register the rotary speed.


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If this means that the possible air gap has to lie within a very small range, then this will also restrict the mechanical tolerances of the motor housing and target wheels to prevent signal dropouts during operation. From the point of view of the motor manufacturer, and even more so the operator, it is therefore better to look for speed sensors with a wider range of air gap.

The primary signal from a Hall sensor loses amplitude sharply as the air gap increases.

For Hall sensor manufacturers this means that they need to provide maximum possible compensation for the Hall signal's physically induced offset drift. The conventional way of doing this is to measure the temperature at the sensor and use this information to compensate the offset, but this fails for two reasons: firstly because the drift does not vary linearly with the temperature, and secondly because not even the sign of the drift is the same for all sensors. Some sensors now offer an integrated signal processor that attempts to correct the offset and amplitude of the Hall sensor signals.

This correction enables a larger maximum permissible air gap at the speed sensor. It has also been possible to markedly increase the signal quality. Both the duty cycle and the phase displacement between the two channels is at least three times as stable in the face of fluctuating air gap and temperature drift.

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In addition, in spite of the complex electronics it has also been possible to increase the mean time between failures for the new speed sensors by a factor of three to four. So they not only provide more precise signals, their signal availability is also significantly better. An alternative to Hall effect sensors with gears are sensors or encoders which use [magnetoresistance]. Because the target wheel is an active, multipole magnet, air gaps can be even larger, up to 4. Because magnetoresistive sensors are angle-sensitive and amplitude-insensitive, signal quality is increased over Hall sensors in fluctuating gap applications.

But many locomotives and electric multiple units EMUs need higher numbers of pulses for proper operation of the traction converter, for instance when there are tight constraints on the traction regulator at low speeds. Such Hall effect sensor applications may benefit from built-in bearings, which can tolerate an air gap many orders of magnitude smaller because of the greatly reduced play on the actual sensor as opposed to that of the motor bearing.

Likewise, the magnetoresistive sensors offer even higher resolution and accuracy than Hall sensors when implemented in motor encoders with integrated bearings. The functional principles of the two encoders are similar: a multichannel magneto-resistive sensor scans a target wheel with teeth, generating sine and cosine signals.


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The precision encoder also possesses amplitude and offset correction functions. This makes it possible to further improve the signal quality, which greatly improves traction regulation. Bearingless speed sensors may be found in almost every wheelset of a rail vehicle.

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They are principally used for wheel slide protection and usually supplied by the manufacturer of the wheel slide protection system. These sensors require a sufficiently small air gap and need to be particularly reliable. View All Diagrams. This product fits vehicle variants. Toyota: 15 models, variants between and Related Products. Alloy Wheel Locks. Lug Nut. TRD Wheel Lock. Remote Engine Starter. Please select a dealer to view local or discounted pricing.