Diagnostic code P1720 for cars of the brand Nissan indicates a critical malfunction in the vehicle speed signal circuit transmitted from the sensor to the transmission control unit. This problem often manifests itself as an illuminated Check Engine light on the dashboard and is accompanied by unstable transmission performance, especially when switching modes or driving at high speeds. Ignoring this signal can lead to the transmission going into emergency mode, which significantly limits driving dynamics and safety.
In modern models such as Nissan Qashqai or Nissan X-Trail, the engine management system and automatic transmission work closely together, using speed data to accurately calculate gear shift timing. A failure in the transmission of this signal disrupts the logic of operation ECU, causing the computer to make incorrect decisions about when to change stages. Understanding the nature of the P1720 error code is the first step to quickly restoring your vehicle's performance and preventing more serious damage.
The nature of the P1720 code and its meaning
Error code P1720 stands for “Vehicle Speed Sensor A is not received” or “Vehicle Speed Sensor A Circuit”. Unlike simple mechanical failures, this error most often indicates a problem in the electrical circuit or the sensor itself, which is located in close proximity to the transmission output shaft.
The transmission control module (TCM) constantly monitors incoming impulses. If there is no signal for a certain time or its amplitude is outside the permissible limits, the system records a failure. It is important to understand that the problem may not only be in the speed sensor, but also in the wiring, connectors, or even in the mechanical part of the transmission if the sensor does not rotate.
Symptoms may vary depending on the car model. In some cases, the driver may notice that the speedometer is showing incorrect data or has stopped altogether while the odometer continues to record mileage. This is a direct result of desynchronization of the signals that the electronics use to display information on the dashboard.
Root Causes and Circuit Components
There are several key reasons why the error may occur P1720. Most often, the problem lies in a physical failure of the vehicle speed sensor (VSS). Over time, the bearing inside the sensor wears out or the magnetic element loses its properties, causing the signal to be interrupted.
The second most common cause is damaged wiring. Vibration, temperature changes and exposure to aggressive environments can lead to abrasion of insulation, oxidation of contacts in connectors or complete breakage of wires. Particular attention should be paid to wiring areas running near hot engine or suspension components, where the risk of mechanical damage is greatest.
Also, do not rule out problems with the control unit. Although less common, software glitches TCM or damage to the internal circuits of the computer itself can lead to false alarms of the sensor. In rare cases, the problem may be due to mechanical wear of the ring gear on the gearbox output shaft, which transmits rotation to the sensor.
- ⚡ Failure of the speed sensor (VSS) itself due to wear or internal damage.
- 🔌 Oxidation or poor contact in the electrical connectors connecting the sensor to the control unit.
- 🔧 Mechanical damage to the ring gear transmitting rotation to the sensor.
- 💻 The transmission control module (TCM) is malfunctioning or the wiring is broken.
Diagnostic methods and troubleshooting
To accurately determine the cause of the error, it is necessary to carry out comprehensive diagnostics using special equipment. The first step is to read the error codes with an OBDII scanner and check the parameters in real time. You need to see if the speed value changes as the car moves, even if the speedometer on the dashboard is not working.
Visual inspection is a mandatory step. It is necessary to check the condition of the speed sensor connector for oxidation, moisture or mechanical damage. The wires must be intact, without signs of rubbing against body parts or the engine. If you find damaged insulation, it may cause a short circuit or signal loss.
A multimeter is often used to check the sensor itself. It is necessary to measure the resistance of the sensor and compare it with the factory values specified in the technical documentation. You can also check the presence of alternating voltage at the sensor terminals when spinning the wheel on a jack. The absence of a signal during rotation indicates a malfunction of the element.
⚠️ Attention: Before starting diagnostics, be sure to disconnect the negative terminal of the battery to avoid short circuits when checking the wiring and connectors.
If a visual inspection and a check with a multimeter do not reveal any problems, it is worth checking the integrity of the circuits between the sensor and the control unit. Testing the wires for breaks and short circuits to ground will help eliminate problems with the wiring. It is also useful to check the grounding of the control unit, since poor ground contact can distort the signals.
- Qashqai
- X-Trail
- Teana
- Juke
- Other
Step-by-step instructions for replacement and repair
If the diagnostics confirm that the speed sensor is faulty, it will need to be replaced. The process is not particularly difficult, but requires accuracy and consistency of actions. First you need to provide access to the sensor, which is usually located on the gearbox housing.
Before starting work, make sure the vehicle is securely supported on stands, especially if you plan to work under the vehicle. Disconnect the electrical connector from the sensor by gently pressing the latch. Then unscrew the mounting bolt and remove the sensor. Be prepared for a small amount of transmission fluid to leak from the hole.
Installation of a new sensor is carried out in reverse order. It is recommended to replace the O-ring (gasket) immediately to avoid oil leaks. Once installed, plug in the connector and make sure it snaps all the way into place. Do not over-tighten the mounting bolt to avoid damaging the sensor body or threads.
☑️ Check before replacement
After replacement, it is necessary to erase the error codes from the control unit’s memory. This can be done using a diagnostic scanner or by disconnecting the battery for a few minutes (although a scanner is preferable for precise cleaning). Next, test drive to ensure that the P1720 code does not return and that the speedometer and gearshift function correctly.
What should I do if the error is returned immediately?
If P1720 appears immediately after replacing the sensor, check that the new element is installed correctly. You may have damaged the wiring during installation or the new sensor may have been defective. It is also worth checking the condition of the ring gear on the gearbox shaft - if it is damaged, the new sensor will not be able to correctly read pulses.
In some cases, adaptation or flashing of the control unit may be required, especially if the problem was related to a software glitch. In such a situation, it is better to contact a specialized service that has the necessary equipment to work with Nissan software.
Effect of error P1720 on transmission performance
The absence of a correct speed signal leads to the control unit losing its understanding of the current vehicle speed. This is critical to the operation of an automatic transmission, since it is based on speed and load that gear shift points are calculated. Without this signal, the TCM goes into limp mode.
In emergency mode, the transmission is locked in one of the gears (usually second or third) to ensure minimal movement. Gear changes occur jerkily or not at all. This creates discomfort for the driver and can lead to increased wear of transmission components due to operation in abnormal conditions.
In addition, the P1720 error affects the operation of other vehicle systems that depend on speed data. This could be the cruise control system that stops working, or the stability control system (ESP) that may turn off or give false warnings. The ABS braking system may also not work correctly because it needs data on wheel speed and vehicle speed.
When replacing a speed sensor on a Nissan, it is recommended to use original spare parts or high-quality analogues from trusted manufacturers, since low-quality sensors can quickly fail or produce incorrect data.
Ignoring the problem can lead to more serious consequences. Long-term operation in emergency mode increases the load on the torque converter and automatic transmission clutches. In the worst case scenario, this may result in the need for a major transmission overhaul, the cost of which will significantly exceed the cost of replacing the sensor.
Table of possible causes and solutions
For clarity, we will present the main causes of error P1720 and how to eliminate them in the form of a table. This will help you quickly navigate the problem and choose the right diagnostic or repair method.
| Cause of malfunction | Symptoms | Elimination method |
|---|---|---|
| Speed sensor (VSS) malfunction | Speedometer does not work, jerks when switching | Replacing the sensor with a new one |
| Broken or short circuited wiring | Random error, no signal | Repair or replacement of damaged wiring sections |
| Oxidation of the sensor connector | Poor contact, unstable signal | Cleaning contacts and treating with anti-corrosion compound |
| Damage to the ring gear | No pulses even with a working sensor | Repair or replacement of gearbox output shaft |
| Control Module (TCM) Failure | Error persists after replacing all components | Firmware update or replacement of the control unit |
When making repairs, it is important to consider that sometimes the problem can be complex. For example, oxidation of the connector could cause a voltage surge that damages the sensor. Therefore, it is always worth checking the entire circuit, and not just one element.
Timely diagnosis and elimination of error P1720 allows you to avoid expensive automatic transmission repairs and return the car to normal dynamics and safe operation.
Prevention and maintenance recommendations
To prevent P1720 code from appearing in the future, it is recommended that you regularly inspect your electrical connectors and wiring. Particular attention should be paid to places where wires pass through moving parts or are exposed to high temperatures. Timely cleaning of contacts from oxidation and dirt significantly extends the service life of sensors.
During routine vehicle maintenance, it is a good idea to check the condition of the speed sensor and its wiring. If you notice signs of wear or damage to the insulation, it is better to replace the problem areas immediately rather than wait for complete failure. This is especially true for cars with high mileage.
Use only high-quality gear oils and change them according to regulations. Contaminated oil can cause carbon deposits to form on the ring gear or inside the sensor, which will impair system operation. Also avoid aggressive driving and sudden throttle changes, which place unnecessary stress on the transmission.
⚠️ Attention: If you notice that the speedometer has started to work intermittently, do not delay diagnosis. Catching the problem early will save you time and money on repairs.
If P1720 appears, do not try to ignore it or drive in limp mode for an extended period of time. This can lead to irreversible consequences for the transmission. It is better to immediately contact specialists or carry out diagnostics yourself if you have the necessary experience and equipment.
Conclusion
Error P1720 on cars Nissan - this is a serious signal that requires immediate attention. Although the problem can often be resolved by simply replacing the speed sensor, accurate diagnosis is the key to successful repair. Ignoring the signal can lead to the failure of expensive transmission components and reduce driving safety.
Regular maintenance, the use of high-quality spare parts and careful attention to the operation of the car will help to avoid such problems. Remember that prevention is always cheaper and easier than major repairs. If you are not confident in your abilities, entrust the diagnosis to professionals who have experience working with Nissan electronics.
Timely elimination of the malfunction will return your car to smooth running, correct operation of the speedometer and confidence in safety on the road. Do not forget that the electronics of a modern car is a complex system where each element plays an important role.
Frequently asked questions (FAQ)
Is it possible to drive with error code P1720?
It is not recommended to drive with error P1720, as the car goes into emergency mode, which limits its dynamics and can lead to jerking when changing gears. This creates a danger in traffic, especially when making a sharp maneuver or overtaking.
How much does it cost to replace a speed sensor on a Nissan?
Replacement costs vary by vehicle model and region. The part itself is relatively inexpensive, but the work may take time. On average, the cost of repairs with spare parts varies depending on the complexity of access to the sensor.
Why does P1720 appear again after replacing the sensor?
If the error returns, the problem may not be with the sensor itself, but with the wiring, connector, or ring gear. It is also possible that the new sensor was defective or was not installed correctly. A more in-depth diagnosis of the entire circuit is required.
Does P1720 affect fuel consumption?
Yes, an error can lead to an increase in fuel consumption, since the control unit cannot optimally select the gear for the current speed. The engine may run inefficiently, increasing fuel consumption.
Do I need to reset the error after repair?
It is imperative to erase the error code from the control unit’s memory using a diagnostic scanner. Without this, the Check Engine Light may stay on even after the problem has been corrected, and the system may continue to operate in limp mode.