Emergency mode automatic transmission: what to do? Automatic transmission enters emergency mode: causes and ways to eliminate them What is automatic transmission emergency mode.

02.07.2020

Reason one: the level is not normal.

This refers to both underfilling and overflowing. All this disrupts the operation of the computer, forcing it to turn on emergency mode. When overflowing, you just need to get rid of the excess. With a lack of fluid, you need to look for the cause of this phenomenon, eliminate leaks.

Reason two: problems with the operation of hydraulics or the mechanical part of the automatic transmission.

This is where renovations can make a big difference in the budget. IN automatic transmission emergency mode can get up due to damage to the gearbox housing itself, malfunction of the friction group. You will have to remove the pan, inspect for the presence of foreign particles - friction dust, chips, metal debris, etc. If all this is present, you will have to examine each element of the transmission separately in search of a cause, or conduct an electronic one. Although scanning does not always accurately determine mechanical damage.

Reason three: problems in the operation of the electronic control system.

The most common reason why Automatic transmission goes into emergency mode. There are several situations that we will analyze separately.

The gearbox is either stable in emergency mode, or goes into it after heating to operating temperatures. The reason may be a malfunction of the temperature sensor, which should be replaced.

The gearbox is either stably in emergency mode, or goes into it unexpectedly and haphazardly. The reason may be damage to the wiring between the blocks, malfunctions of some chips connecting the blocks. It is eliminated by ringing the wiring, trial replacement of chips in turn, to identify a faulty one.

The gearbox is either stable in emergency mode, or goes into it suddenly, but not when shifting gears. The reason may be faulty sensors: camshaft, throttle, air flow, ABS. What exactly is wrong helps to identify the scan.

When the lever is moved to "D", a thud is heard, after which it turns on automatic transmission emergency mode. Or this mode is activated when switching from first to second gear. The reason is the breakdown of the rotation sensors of the input or output shaft. It may show a scan. Eliminated by replacing sensors.

The gearbox is stably in emergency mode, does not want to leave it under any action. Control unit defective. Scans don't always show this, so a trial block replacement helps.

Automatic transmission switched to emergency mode, Video

We have considered typical cases where Automatic transmission switched to emergency mode. But it would be useful to note that the automatic transmission is such a complex mechanism that the same sign can correspond to different damages. And only a specialist can make an accurate diagnosis. In order not to overpay for repairs, you should still check the car in a car service.

To begin with, today there are several types of automatic transmissions:, and. At the same time, various malfunctions are characteristic of each type of gearbox, and quite often and regardless of the type of gearbox, the machine “gets up” in emergency mode.

In this article, we will consider a classic automatic transmission with (hydromechanical automatic transmission), what is an emergency mode for an automatic machine of this type, and also why the automatic transmission goes into an “accident”.

Read in this article

Automatic transmission emergency mode: what is it

So, the transition of the gearbox to emergency mode occurs if there is a breakdown or malfunction of the unit. In other words, the activation of the emergency mode on the machine signals the occurrence of certain problems.

At the same time, notifications or warning lights for check AT, HOLD, check engine, etc. light up on the instrument panel. If the automatic transmission "got" into an accident, the car stops accelerating dynamically, the sharp response to pressing the gas pedal disappears, gears do not change in D mode, etc. The fact is that in this mode the car starts and moves only in third gear.

At the same time, the emergency mode itself can be considered protective, since its inclusion allows you to prevent a number of more serious damage to the automatic transmission. Even the emergency mode of the automatic transmission retains the ability to continue driving on its own to the nearest service station.

In other words, you can’t constantly drive in automatic transmission emergency mode, but you can get to a car service without a tow truck. Now let's look at why and when the emergency mode of the automatic transmission is activated, the reasons for its activation, as well as options and ways to solve the problem.

Automatic transmission goes into emergency mode: reasons

Let's start with the fact that modern automatic transmissions are quite complex units. At the same time, as practice shows, there are several main reasons why the automatic transmission “falls” into an accident.

First of all, a low or high ATF level in the box can lead to malfunctions, as a result of which the emergency mode is activated at the command of the automatic transmission ECU.

Underleveling can occur as a result of leaks, while overleveling is often due to errors during box maintenance. For example, overflowing fluid into an automatic transmission leads to foaming, and a shortage leads to oil starvation.

The result is a decrease in pressure and deterioration of lubrication, rubbing surfaces at the points of contact wear out heavily. Electronics fixes deviations from the norm, emergency mode is activated, an error is registered in the ECU by the box.

For this reason, if the box went into emergency mode, you need. It is also recommended to carry out automatic transmission self-diagnosis (if possible and if you have the skills to carry out this operation).

Another reason may be malfunctions associated with the operation of hydraulic devices, as well as problems in terms of mechanics. For example, the emergency mode of the automatic transmission may turn on if the body of the automatic transmission is damaged, slip, worn, skidding or “burnt”, there are problems with the gas turbine engine, etc.

In this case, it is necessary to carry out an in-depth diagnosis of the automatic transmission. The check begins with computer diagnostics, but such a scan does not always provide a clear idea of the nature and cause of the malfunction.

In this case, it may be necessary to dismantle the gearbox pan in order to inspect for contamination, friction dust, metal chips. In some cases, for troubleshooting, it will also be necessary to completely remove the automatic transmission and disassemble the unit in order to assess the degree of wear and condition of individual elements.

The third reason for the transition of the machine to emergency mode is problems with the automatic transmission electronic control system. In this case, the symptoms may be different, the malfunction may be "floating" or persist permanently.

For example, it works fine on a cold box, but after warming up, the automatic transmission immediately goes into emergency mode. In such a situation, the culprit is often the temperature sensor, which needs to be replaced.

If the gearbox “falls” into emergency mode unexpectedly, that is, regardless of various factors and conditions, then the cause may be a banal damage to the wiring, problems with contacts, etc. In this case, an experienced diagnostician checks the wiring and connections.

In addition, if the transmission goes into emergency mode unexpectedly, and this transition does not occur during a gear change, then the sensors (camshaft sensor, etc.) may be the cause. In this case, you need a complex.

Also, often problems with automatic transmission occur when the driver moves the selector to position D or at the moment of switching from 1st to 2nd gear. At this time, a blow is heard in the box, then the emergency mode of the automatic transmission is activated. In this situation, the probability of damage to the shaft rotation sensors is high.

It should be remembered that the contacts of the sensors can oxidize or break, thin wiring often breaks, cables wear out, etc. As a result, the connection is lost. This is also one of the answers to the question why the automatic transmission went into emergency mode.

For automatic transmission diagnostics in emergency mode, it is better to read errors using a diagnostic scanner, since automatic transmission self-diagnosis is not always able to detect a problem. If the diagnostics do not give results, then the breakdown should be looked for manually (by checking the sensors, “ringing” the circuits, etc.).

If the automatic transmission is in emergency mode all the time, while restarting the engine or resetting errors does not help, and the sensors and wiring are in order, then the possibility of problems with the gearbox ECU should not be ruled out. In this case, they often resort to the method of replacing the block with a known working one in order to check.

A common cause of automatic transmission failure is contamination / damage to the channels, the appearance of scoring in the valve plate, malfunctioning solenoids. In this case, the machine operates in emergency mode. The reason is increased sensitivity to the quality of the oil in the automatic transmission and fluid pressure.

To avoid such a breakdown, it is necessary in a timely manner. You also need to use only such ATF fluid that the manufacturer allows for use in a particular type of automatic transmission.

Remember, mixing transmission fluid from different manufacturers can cause the additive packages to react, as a result of which the properties of the oil will change and the automatic transmission will malfunction.

It turns out that if the automatic transmission has switched to emergency mode, the oil level is normal, but its color, smell, viscosity and general condition are in doubt, then you should diagnose the box and be prepared, at least

What is the result

As you can see, there are a lot of reasons why the emergency mode of the automatic transmission is turned on. At the same time, even rare inclusions of this mode, which are eliminated by restarting the internal combustion engine, indicate that there is already a problem with the machine and with a high degree of probability it will only progress.

As for the errors and failures themselves, a long drive in a car in which the box has switched to emergency mode is not allowed. In other words, in this mode, you can only get to the car service, while avoiding loads on the automatic transmission.

Let us remind you once again that until the breakdown or malfunction is eliminated, the regular operation of a car with an automatic gearbox in emergency mode is prohibited! Moreover, if the automatic transmission has already “gone” into an accident, but while driving, extraneous sounds are heard during the operation of the machine (grinding, hum, crunch, bumps), then it is better to refuse to drive to the service on your own.

The best rhenium in such a situation would be to call a tow truck, since towing a car with a faulty machine gun without hanging the drive wheels can lead to even more serious consequences for the automatic transmission, which is already faulty in itself and has switched to “emergency” mode.

What to do if the machine goes into an accident?

In the event of a malfunction of the valve body solenoids, wiring problems, a short movement should not turn into sad consequences, since the automatic transmission ECU selects the safest mode of operation. The concept of emergency mode means that the car moves only at one of the speeds. If the automatic transmission got into an accident and blocked the second or third gear, follow the following algorithm of actions:

stop and check the oil level in the automatic transmission. If the transmission design does not include a dipstick, look under the vehicle. The leaking transmission fluid is red, the characteristic smell of burnt oil indicates that it is not worth going further;
move the wiring harnesses going to the automatic transmission. If the reason is poor contact of the engine compartment wiring, with the proper combination of circumstances, you will be able to temporarily remove the box from emergency mode;
turn off the engine, turn off the ignition for 1-2 minutes. If it does not help, disconnect the negative battery terminal for 2-3 minutes. On some cars, such manipulations really allow you to remove the emergency mode;
if the oil level is correct, continue driving to a safe stop or the nearest service station. At the same time, you need to drive as carefully as possible. Do not press the pedal to the floor, driving the engine speed into the red zone.

Possible causes of malfunction

Going beyond the operating temperature, in other words - overheating.
Insufficient ATF fluid level, resulting in a decrease in oil pressure in the valve body. Often, a breakdown does not occur at lightning speed and begins to manifest itself with a belated shifting of gears, shocks, shocks when switching.
Fault . For an accurate selection of the moment of gear shifting, effective acceleration and fuel economy, the automatic transmission electronic control unit is based on the readings of either DBP, TPS. Incorrect operation of the sensors ignites the Check Engine on the dashboard, but can also cause jolts, bumps and the automatic transmission to go into emergency mode.

Where should you start diagnosing?

Only the earliest models did without an electronic component. All other units, depending on the model and year of manufacture of the automatic transmission, have an electronic "brain" and a self-diagnosis system. If the automatic transmission on your car got into an “accident”, you should start with computer diagnostics. You will need a device to connect to the diagnostic socket and the appropriate software for reading information. After reading the current fault codes, look for their decryption on the Internet in order to more clearly represent the direction of further searches. The most common causes of automatic transmission emergency mode:

incorrect gear ratio of individual gears;
malfunctions in the electrical circuit of the solenoid valves;
discrepancy between the speed of the input and output shaft of the gearbox.

In case of an error on the solenoid valves, do not rush to disassemble the automatic transmission. It is necessary to diagnose the wiring and the computer of the automatic transmission. If you know, then easily check the resistance of the wires, the shaft rotation sensor. You need to remove the connectors from the box body, as well as the automatic transmission control unit connector. Check the wires not only for an open, a short to “-”, “+”, but also for a short to each other. This is quite likely in the case of grinding or melting of the insulation. Also, be sure to check whether power is “coming” to the connector of the control unit and whether there is a reliable “ground”. The location of the control units, the pinout of the connectors and the colors of the wires can be found in the manual for the repair and operation of the car.

The video by Ivan Saichenko shows how to properly check the wiring if the automatic transmission is in emergency mode.

Visual inspection and soldering of contacts

When looking for the cause of the emergency mode of an automatic transmission, pay attention not only to the wiring harnesses in places where they come into contact with the body, but also to the power connectors themselves. Sometimes, due to corrosion, inaccurate removal / installation, the pins of the connectors simply break off. Automatic transmission can go into emergency mode even in the presence of oxides on the contacts.

On many Audi, Mercedes, the automatic control unit is located under the front seat, where moisture often gets in. Before disassembling the automatic transmission, it will be useful to pull out the control unit board. Even if there are no oxides on it, we recommend that you make sure that there are no microcracks in the soldering points, and, if necessary, solder the main contacts.

We recommend disassembling the box for troubleshooting the hydraulic unit, checking solenoids, clutch packs only after a complete diagnosis of electrical circuits and easily accessible elements.

In the event of emergency situations, when the normal operation of the “automatic” box is not possible, the ECU turns on the emergency mode of the automatic transmission and signals this by turning on the corresponding lamp on the dashboard.

What caused this? Can problems be fixed on the spot?

An automatic gearbox, subject to the operating conditions recommended by the manufacturer, will last 250 thousand kilometers or up to 5 years. In fact, the actual service life depends on many factors - driving style, service intervals, etc. Automatic boxes are equipped with an electronic control unit that is responsible for operating modes and performs all the necessary procedures for shifting gears. In the event of emergency situations, when the normal operation of the “automatic” box is not possible, the ECU turns on the emergency mode of the automatic transmission and signals this by turning on the corresponding lamp on the dashboard.

Why does the automatic transmission go into emergency mode

The reasons for the transition of the automatic transmission to emergency mode may be as follows:

Lack of transmission fluid. If there is not enough oil in the automatic transmission, the electronic control unit switches on the emergency operation.
Malfunctions of the electronic control system. Automatic transmission errors can be caused by automatic transmission computer failures.
Problems in the operation of hydraulics or mechanical elements of the automatic transmission - malfunctions of the torque converter, wear of friction clutches, other hydraulic or mechanical damage include emergency operation of the automatic transmission.

Transmission oil leak

The "automatic" box goes into emergency mode in case of a lack of gear oil. A leak can occur due to failure of the seals, damage to the housing, malfunctions of the automatic transmission valve body. If, during inspection, oil smudges are found in the pit or on the lift, then it is necessary to contact specialists as soon as possible to troubleshoot. Most often, the transmission oil and seals will need to be replaced. In a specialized auto repair shop, masters will be able to determine the causes of leaks and eliminate them.

Control unit malfunctions

Abnormal operation of the transmission ECU can lead to the activation of the emergency mode of the automatic transmission. Typical malfunctions of the control unit are the wrong choice of revolutions, gear shift blocking. Troubleshooting will require computer diagnostics, replacement of failed elements or the entire unit, damaged cables, contact group.

Failure of hydraulic or mechanical parts

The self-diagnostic system, upon detection of malfunctions in the mechanical or hydraulic part of the box, will ensure the transition of the automatic transmission to emergency mode. Common problems are clutch wear, valve body or torque converter malfunctions. After diagnosing the automatic transmission, it will be possible to establish the reasons for the failure of individual parts.

Features of automatic transmission emergency mode

If the automatic transmission is in emergency mode, then you can continue driving only in third gear. The speed of the car in this case is limited - no more than 60 km / h. Starting a car in emergency mode (for example, in winter) is quite problematic.

The emergency mode of operation of the “automatic” box is designed so that you can get to the service station without calling a tow truck. Operation of the car in emergency mode is not allowed, as it can lead to serious damage and, as a rule, expensive overhaul of the automatic transmission. Therefore, in the event of activation of the emergency mode, it is necessary to determine the reason for the entry of the "automatic" box into this mode as soon as possible and eliminate the malfunctions.

What to do when you turn on the emergency mode

Don't know what to do in emergency automatic transmission mode? There are two options for solving the problem:

Call the master. The specialist will diagnose the automatic transmission, determine why the automatic transmission has entered emergency mode, and, if possible, eliminate the malfunctions on the spot.
Get to the car service. In 3rd gear, you can get to the service station on your own, where the masters will diagnose and repair the automatic transmission of the car.

Of course, you can immediately go to the service station for diagnostics and repairs, but it will be more convenient to call an auto electrician with a visit to the place of breakdown. The master will perform diagnostics and, if the breakdowns can be fixed immediately, will perform the necessary work. So you can save time on a trip to the service in case of minor breakdowns, which, after diagnostics, an on-site auto electrician can fix on the spot.