Fault code P2711 – unexpected mechanical gear disengagement

Fault code P2711 is called “Unexpected Mechanical Gear Disengagement” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P2711

This diagnostic trouble code (DTC) is a generic transmission code. Error P2711 is considered a generic code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly from model to model.

A fault code appears when the PCM control module detects a problem between the output and input shaft speed signals. The control module perceives this problem as a mechanical gear disconnect. This may result in poor gear shifting and drivability problems.

Unexpected mechanical gear disengagement occurs when the PCM detects that the output shaft speed sensor is defective. The system detects the error when the gears are ready or nearly ready to shift.

The PCM control module controls hydraulic pressure and electronic solenoids to select and hold the various gears in the transmission. When the PCM detects that the transmission is not holding the requested gear, it sets code P2711.

When it is mechanically disengaged, the output speed does not increase gradually as it does during normal operation, so an error occurs in the system. For some makes and models, it will take several system failures before the indicator lamp (MIL) lights up.

Symptoms of vehicle malfunctions

The main signal that an error P2711 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
2. The transmission does not shift properly.
3. Jerking when shifting or driving.
4. Increased fuel consumption.
5. Severe speedometer fluctuation or complete failure.
6. Floating revolutions, and attempts to stall when idling.
7. There may be no symptoms other than a stored fault code.

A stored fault code P2711 is considered serious, as it can cause drivability and safety problems with the vehicle. The conditions that have contributed to the stored code must be corrected as soon as possible.

Factors that can cause this error code

The error code P2711 can mean that one or more of the following problems have occurred:

• Low transmission fluid level.
• Heavy contamination of transmission fluid.
• Mechanical failure inside the transmission.
• Faulty input or output shaft speed sensors.
• Short circuit or damage to wiring harness.
• Faulty wiring connector.
• Sometimes faulty PCM module is the cause.

How to fix or reset OBD-2 code P2711

Some suggested steps for troubleshooting and fix the error code P2711:

1. Read all stored data and error codes with an OBD-II scanner.
2. Clear the error codes from the computer memory.
3. Test-drive the vehicle to find out if error P2711 appears again.
4. Check the level and quality of the transmission fluid.
5. Check the input and output shaft speed sensors.
6. Visually inspect the appropriate wires and connectors for damage.
7. If necessary, replace the defective parts.
8. Test the transmission for internal mechanical problems.
9. Test the transmission control module (TCM).

Diagnose and repair of problems

The first thing to do is to check the level and quality of the transmission fluid and, if necessary, top up or replace it. When replacing the transmission fluid, the filter must also be changed.

Next, when diagnosing code P2711, it is worth checking the electrical part for damage. In today’s vehicles, electrical and electronic signals require good cabling for proper data transmission.

Any faults, such as breaks, disconnected connectors or corrosion, can interrupt signals, leading to transmission control failures. Next, check the battery, as some PCM and TCM modules are sensitive to low voltage.

If the battery is low, the system may detect this as a failure. Make sure the battery is delivering at least 12 volts and that the alternator is running properly, a minimum of 13 volts at idle.

If there are no problems at this point, check the input shaft speed sensor and output shaft speed sensor. If no sensor problems are found, then internal diagnostics of the friction components, gears, valve housing and other transmission parts should be performed.

The transmission control module (TCM) fails very rarely, but it can happen. Therefore, when diagnosing error P2711, it must be checked if all other steps have already been completed.

On which vehicles does this problem occur most frequently

Fault code P2711 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

• Audi (A3, TT)
• Citroen
• Peugeot (508)
• Skoda (Yeti)
• Volkswagen (Passat, Scirocco)

Fault code P2711 can sometimes be found with other errors. The most common are the following: P2793, P2794, P2795.

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