Speed ​​sensor Opel Astra H

Diagnostics and replacement of the automatic transmission input speed sensor

It often happens that you blame the car for an engine failure, poor-quality fuel that was filled at a gas station, although in fact the input shaft speed sensor in the automatic transmission simply failed. Damage can be mechanical, leakage of the housing or internal oxidation of the contacts. But first things first.

Input shaft speed sensor, automatic transmission

The automatic transmission has two speed sensors.

• one sets the number of revolutions of the input shaft;
• the second one freezes it.

Attention! For automatic transmissions on reversible vehicles, the sensor measures the number of revolutions of the differential.

The input shaft sensor is a non-contact magnetic device based on the Hall effect. It consists of a magnet and a Hall integrated circuit. This equipment is packed in a sealed box.

Information from these sensors enters the electronic control computer of the machine, where it is processed by the machine. If there is any malfunction in the sensor, crankshaft or differential, the automatic transmission goes into emergency mode.

If the ECU does not find problems according to the sensor readings, and the vehicle speed decreases or does not increase, Check Engine is on, then the malfunction may be in the automatic transmission input shaft sensor. But more on that later.

Principle of operation

As I already wrote, the device records the number of shaft revolutions after switching to one of the automatic transmission gears. The working process of the Hall sensor is as follows:

1. During operation, the electromagnetic sensor creates a special electromagnetic field.
2. As the wheel protrusion or gear tooth of the "driving wheel" mounted on it passes through the sensor, this field changes.
3. The so-called Hall effect begins to operate. In other words, an electrical signal is generated.
4. It turns and enters the automatic transmission electronic control unit.
5. Here it is read by the computer. A low signal is a valley and a high signal is a ledge.

The drive wheel is a normal gear mounted on the device. The wheel has a certain number of bumps and depressions.

Where is

The automatic transmission output shaft speed sensor is installed on the machine body next to the air filter. Instruments for measuring the number of revolutions of the input and output shafts differ in the number prescribed in the catalog. For Hyundai Santa cars, they have the following catalog values: 42620 and 42621.

Attention! These devices should not be confused. There is a lot of information on the Internet about these devices, but often inexperienced writers do not distinguish between them and write as if they are one and the same. For example, information from the last device is needed to adjust the lubricant pressure. These automatic transmission sensors have different proportionality between the revolutions and the signals that come from them.

It is these devices that are directly connected to the automatic transmission control unit. The devices themselves are repairable. It will only be necessary to check for cracks in the casing.

Diagnostics

If you are a beginner car enthusiast and do not know how to check and where to start looking for errors in the device, then I advise you to call the contacts and measure the DC or AC signals. For this you use a multimeter. The device determines the voltage and resistance.

Diagnostics can also be carried out by jolts, jolts felt by the driver when switching the selector backstage to the “D” mode. A faulty sensor gives incorrect rotation measurement signals and, as a result, low or excessively high pressure is created, causing acceleration drops during acceleration.

Experienced mechanics are of the type of visual diagnostics, watching for the appearance of errors on the dashboard. For example, the following indicators on the monitor may indicate problems with the input shaft sensor:

Automatic transmission can start emergency mode or include only third gear and no more.

If you check with a scanner with a laptop at hand, the following error "P0715" will be displayed. In this case, you need to replace the automatic transmission input shaft sensor or change the damaged wires.

Measuring the rotation of the automatic transmission output shaft

Earlier I wrote about the automatic transmission output shaft speed sensor, comparing it with a device that fixes the speed of rotation. Now let's talk about its shortcomings.

P0720 detects a fault in the output shaft speed sensor. The box ECU receives a signal from the device and decides which gear to shift into next. If there is no signal from the sensor, the automatic transmission goes into emergency mode, or an experienced mechanic diagnoses error 0720 with a scanner.

But before that, the driver may complain that the car is stuck in one gear and does not shift. There are errors in overclocking.

Definition of gear shifting

Now you know all about the sensors that monitor the speed of rotation of the input and output shaft. Let's talk about another important device - the gear shift detection device. It is located next to the selector. The choice of speed and the ability of the driver to switch one or another gear depend on it.

This device controls the position of the gear selector. But sometimes it breaks down and then the driver observes:

• incorrect designation of the gear you have chosen on the dashboard monitor;
• the letter of the selected gear is not displayed at all;
• change of speed occurs in jumps;
• transmission delay. A car, for example, can stand still for a while before moving in a certain mode.

All these malfunctions occur due to:

• drops of water falling inside the case immediately violate the tightness;
• dust on contacts;
• wear of contact sheets;
• contact oxidation or contamination.

To correct errors that have arisen due to incorrect operation of the sensor, the device must be disassembled and cleaned. Use regular gasoline or kerosene to clean the contacts. If you need to solder loose pins, do so.

Use a penetrating lubricant to clean the contacts. But experienced mechanics and I do not recommend lubricating the surface with Litol or Solidol.

Features of obtaining data on the position of selectors in some car models

The following vehicle modifications have serviceable sensors:

• OpelOmega. The blades of the selector position detection devices are thick. Therefore, they rarely fail. If they crack, light soldering will repair the contacts;
• Renault Megan. Car owners of this machine may experience jamming of the input shaft sensor. Since the board is packed in fragile plastic, which very often melts under the influence of high temperatures;
• Mitsubishi. Mitsubishi automatic transmission input shaft sensors are renowned for their reliability. To correct its poor performance, it is necessary to disassemble it and blow it with air, and clean the contacts with kerosene.

If cleaning, bleeding the automatic transmission input shaft sensors does not help, then it will need to be replaced. Have you ever changed such devices? If not, then sit down. I'll tell you how it's done by hand.

Replacing the automatic transmission input shaft sensor

Attention! In rare cases, drivers of the second generation Renault Megane, and other vehicles, may not notice any changes in the operation of the automatic transmission. The gradual increase in this problem will lead to the fact that the car can go into emergency mode somewhere in the middle of heavy traffic. This will create an emergency. Therefore, it is important to deliver the car for maintenance to the service center on time.

Repair and replacement of a damaged output shaft speed sensor is carried out as follows:

1. Open the hood and remove the air filter to gain access to the device.
2. Disconnect it from the connectors.
3. Check housing for tightness. If everything is in order, open the device.
4. Check device voltage and resistance.
5. If the gear teeth are worn out, replace them with new ones.
6. Check the contacts and clean them.
7. If the device is in poor condition, replace it and install a new one.
8. After completing all the procedures for installing a new one, check the automatic transmission for errors with a scanner.
9. If errors persist, check terminals and cables. They can be chewed on by mice or cats.
10. Replace them if necessary.

Automatic transmission shaft speed sensor

A modern automatic transmission is a complex assembly. Depending on the type of automatic transmission, it is a whole complex of electronic, mechanical and hydraulic components and assemblies.

By controlling the automatic transmission ECU, it controls the operation of the transmission, receives signals from numerous sensors of the gearbox, automatic transmission and ECM, and also generates control signals according to the algorithms prescribed in the automatic transmission memory.

In this article, we will discuss what an automatic transmission input speed sensor is, what malfunctions occur with this element, and how to diagnose problems that an automatic transmission speed sensor can cause.

Input shaft speed sensor (input speed) automatic transmission: purpose, malfunctions, repair

Among the various sensors that closely interact with the automatic transmission computer and can cause malfunctions, the automatic transmission input and output shaft sensors should be singled out separately.

If it is an automatic transmission input speed sensor, its job is to diagnose problems, monitor shift points, adjust operating pressure, and perform a torque converter lock-up (TLT).

Signs that the automatic transmission input speed sensor is defective or not working properly are a noticeable deterioration in vehicle dynamics, poor and weak acceleration, a “tick” on the instrument panel, or the automatic transmission in emergency mode.

In such a situation, many drivers believe that the cause is poor fuel quality, a malfunction in the engine power system, or contamination of the transmission oil.

At the same time, it should be noted that instead of cleaning the nozzle or changing the oil in the automatic transmission, it may be necessary to perform in-depth diagnostics of the automatic transmission or check the speed sensor of the input shaft of the gearbox.

If the emergency lamp is constantly on / flashing, the gearbox was in an accident (only third gear is engaged, the shift is tight, shocks and bumps are noticeable, the car does not accelerate), then you need to check the input shaft sensor.

Such a check often allows you to quickly identify the problem, especially if it is related to the operation of the automatic transmission shaft speed sensor. By the way, in most cases, a faulty automatic transmission input speed sensor should be replaced with a new one or a known good one.

As a rule, although the sensor is a reliable and fairly simple electronic device, failures can occur during operation. Faults in this case usually boil down to the following:

• The sensor housing is damaged, there are defects, there were problems with its sealing. As a rule, the case can be damaged as a result of significant temperature changes (strong heating and intense cooling) or mechanical influences. In this case, a replacement with a new element is necessary.
• The sensor signal is not constant, the problem is floating (the signal disappears and appears again). In such a situation, both wiring problems and oxidation / damage to the contacts in the sensor housing are possible. In this case, in some cases the sensor cannot be replaced. To repair a defective element, you need to disassemble the case, clean the contacts (solder if necessary), after which the contacts are crimped, insulated, etc.

Then you need to remove the sensor and check it with a multimeter, comparing the readings with those indicated in the instructions. If deviations from the norm are noted, replace or repair the automatic transmission input shaft sensor.

To summarize

As you can see, the automatic transmission shaft speed sensor is a simple element, while the quality of the automatic transmission as a whole directly depends on its serviceability. If malfunctions and deviations from the norm are noted (the car accelerates poorly, the “check” is on, the HOLD indicator flashes, the gears shift sharply and abruptly, the shift point is changed, delays are observed, etc.), then as part of a comprehensive automatic transmission diagnostics, eliminate possible malfunctions of the frequency sensor rotation of the input shaft of the automatic transmission.

In this case, the replacement itself can only be done in a garage. The main thing is to study the manual separately in order to get all the necessary information about the installation site, the features of removing and subsequent installation of the automatic transmission input shaft sensor.