Car owners Nissan Primera P12 with a CVT or a classic automatic transmission, they often encounter an emergency situation when the Check Engine indicator lights up on the dashboard and the scanner issues a code P1720. This malfunction indicates a violation in the vehicle speed sensor signal circuit, which critically affects the operation of the transmission. Without the correct signal, the electronic control unit cannot determine the current speed, which leads to failures in gear shifting.
Ignoring this problem can lead to serious consequences for the gearbox, including increased wear of the clutches, overheating of the valve body, and even complete failure of the unit. In the case of Nissan Primera P12 The protection system often puts the transmission into limp mode, limiting the number of available gears and preventing the torque converter lock-up from operating. You need to understand that P1720 - this is not just a lighted lamp, but a signal of the loss of critical information for controlling the power unit.
The essence of the P1720 code and the operation of the speed sensor
Error code P1720 stands for Vehicle Speed Sensor Circuit. In the context of the model Nissan Primera P12 We are talking about a sensor mounted directly on the gearbox housing. This element is responsible for converting the mechanical rotation of the output shaft into electrical impulses that are read by the transmission control module (TCM).
The control system constantly compares the signal from the speed sensor with data from other sensors, for example, the input shaft speed sensor or engine speed sensor. If the signal is missing, interrupted or has an inappropriate amplitude for a certain time, the control unit records the error and stores it in memory. No signal makes it impossible to correctly control the gear shift point and line pressure.
A special feature of this model is that if an error occurs P1720 The car may lose traction at certain speeds or begin to jerk when accelerating. The electronics do not understand how fast the car is moving and tries to keep the engine speed at unacceptable values, which causes jerking. It is necessary to carefully check the integrity of the wiring and the sensor itself before drawing conclusions about a malfunction of the control unit.
The main reasons for the malfunction
Reasons for the code P1720 there may be several, and they range from trivial contact problems to serious mechanical damage. The most common problem is failure of the speed sensor due to wear or moisture in the connector. When used on roads with reagents, corrosion of contacts occurs much faster.
The second common cause is a break or short circuit in the wiring harness running from the sensor to the control unit. Vibrations, temperature changes and mechanical damage can damage the integrity of the insulation or the wires themselves. It is also worth paying attention to the condition of the connector: oxidation of the contacts often simulates an open circuit, although the sensor itself is working.
- 🔌 Oxidation or contamination of contacts in the speed sensor connector
- 🔧 Mechanical damage to the sensor housing or magnetic rotor
- ⚡ Short circuit in the wiring between the sensor and the TCM
- 🧠 Transmission control unit software failure
Sometimes the problem lies not in the electrics, but in the mechanical part of the transmission. If the gear from which the signal is taken (if it is separate from the sensor) is chipped or worn, the pulses will be unstable. In rare cases, the culprit is a malfunction of the control unit itself, which incorrectly processes incoming data.
⚠️ Warning: Do not try to fix the error P1720 a simple memory reset by the scanner. If the physical cause of the malfunction (broken wire or broken sensor) is not eliminated, the code will return immediately after a few kilometers of driving, and the problem will worsen.
Vehicle symptoms and behavior
When the system records an error P1720, behavior Nissan Primera P12 is changing dramatically. The first and most noticeable sign is the check engine light and transmission light (usually yellow with an "AT" or gear icon) coming on. In some modifications, the "Service Engine Soon" indicator may light up.
The main symptom is the transmission going into emergency mode. In this mode, the vehicle can only be started in second or third gear to ensure minimal movement to the repair site. When trying to move away, you may feel a strong jerk or lack of response to the gas pedal. Acceleration dynamics drops sharply, and fuel consumption increases.
In addition, there may be no gear changes at all. The gearbox may get stuck in one gear, regardless of engine speed. When braking, the engine may stall because the torque converter lockup does not disengage in time due to lack of speed data. You need to carefully monitor the vehicle's performance in order to notice these signs in time.
- 🚗 Jerks and jolts when changing gears or driving
- 📉 Inability to accelerate above 40-60 km/h due to ECU limitations
- ⛔ Failure to engage reverse gear or its sudden engagement with impact
- 🔥 Overheating of the transmission fluid due to incorrect operation of the valve body
Step-by-step system diagnostics
To start diagnosing, you need to connect a professional diagnostic scanner and make sure there is a code P1720. Check the current speed sensor parameters in real time. When the car is on a lift or in motion (if it is safe), the speed value should change smoothly and correspond to the speedometer readings.
If the signal is missing or “jumping”, start with a visual inspection. Disconnect the speed sensor connector and inspect the contacts for oxidation, moisture or mechanical damage. Use a multimeter to check the resistance of the sensor itself. Normal values are usually in the range of 500 to 2000 ohms, but the exact numbers depend on the specific year of manufacture Nissan Primera P12.
Next, check the integrity of the wiring. Measure the voltage on the supply wire (usually +5V or +12V depending on the circuit) and make sure there is ground. Check the signal line for a short to ground or short to power. Clean the contacts and spray them with a special electrical contact spray before reassembling.
⚠️ Attention: When checking the wiring, be sure to disconnect the vehicle battery. Working with a live electrical circuit can damage the transmission control module and create new faults.
If the electrical part is ok but the error persists, the problem may be mechanical. Remove the sensor and check for the presence of a magnetic rotor or ring gear. Make sure there are no chips, dirt or metal shavings that could shield the signal. In some cases, it is necessary to replace the sensor even if there is a signal, since its characteristics may be unstable.
- 🔍 Visual inspection of the connector and wiring harness for damage
- 📏 Measuring sensor resistance with a multimeter
- 🔌 Checking the supply voltage and ground on the connector
- 🧹 Cleaning contacts and checking the presence of a magnetic rotor
- Yes, it's already been repaired
- Yes, I'm planning a renovation
- No, but I'm afraid
- No, everything works fine
☑️ P1720 diagnostic checklist
Sensor repair and replacement procedure
If the diagnostics confirm that the speed sensor is faulty, it must be replaced. On Nissan Primera P12 The sensor is usually located on the top of the transmission and is accessible without removing the unit. To work, you will need a basic set of tools, including wrenches 10 and 12, as well as a new original sensor or a high-quality analogue.
The replacement process begins by removing the negative terminal of the battery to de-energize the system. Find the speed sensor, disconnect the electrical connector by pressing the latch. Unscrew the fastening bolt and carefully remove the sensor from its seat. Be careful not to damage the O-ring or drop the sensor inside the box.
Before installing a new sensor, clean the seat from dirt and old grease. Install a new O-ring (if it is not included with the sensor). Insert the sensor into place, tighten the mounting bolt to the recommended torque and connect the electrical connector until a characteristic click is heard. Don't forget to replace the battery terminal.
Do I need to reset adaptations after replacement?
After replacing the speed sensor, it is highly recommended to perform a transmission adaptation reset procedure. This can be done using the diagnostic scanner by selecting the "Reset Adaptive Values" or "Clear Learn Values" function. Without a reset, the box may not work correctly for several hundred kilometers, since the control unit will use old, incorrect data.
After replacement, be sure to check the operation of the system. Start the engine, warm up the transmission and drive a short distance. Make sure that shifts occur smoothly and that the speedometer shows the correct speed. If the error P1720 disappeared and does not return, the repair can be considered complete.
| Parameter | Meaning | Comment |
|---|---|---|
| Sensor type | Magnetoresistive | Sensitive to magnetic field |
| Resistance | 500–2000 Ohm | Range for a healthy sensor |
| Location | Gearbox housing | Upper part of transmission |
| Signal | Pulse | Frequency depends on speed |
| Original number | 33700-AX00A | Example number for P12 (check by VIN) |
⚠️ Attention: Using non-original or cheap analogues of the speed sensor may lead to the reappearance of the error P1720 in the near future. Electronics Nissan is very sensitive to signal quality, and cheap sensors often have unstable characteristics.
When purchasing a speed sensor, be sure to check the part number with your vehicle's VIN. Even on Nissan Primera P12 In different years of production, different modifications of sensors with different connectors or characteristics could be installed.
Resetting errors and adapting the system
After eliminating the physical cause of the malfunction and replacing the sensor, it is necessary to delete the error code from the memory of the control unit. This is done using a diagnostic scanner connected to the OBDII connector. Select "Clear DTC" or "Reset Fault Codes" from the menu.
However, simply removing the error may not be enough. The transmission control unit stores in memory adaptation values that were calculated based on incorrect data from the sensor. These values can influence line pressure and switching points. To restore normal operation, a training (adaptation) procedure is required.
The adaptation process usually includes warming up the transmission to operating temperature and sequentially driving the vehicle in various modes: starting, accelerating to 60 km/h, and engine braking. In some cases, the scanner allows you to run an automatic learning procedure that will calibrate the sensors in several cycles.
- 🔌 Connecting a scanner and clearing error memory
- 🔄 Starting the procedure for resetting transmission adaptations
- 🚗 Test drive to teach the control unit new parameters
- 📉 Monitoring that the error does not reappear
If after all procedures there is an error P1720 returns, this may indicate deeper problems such as a faulty TCM or mechanical damage inside the transmission. In this case, it is recommended to contact transmission repair specialists for in-depth diagnostics.
Timely replacement of the speed sensor and reset of adaptations is the key to a long life of the gearbox. Nissan Primera P12. Ignoring the error can lead to costly repairs to the valve body or the entire unit.
Electrical prevention and care
To avoid the error reappearing P1720, it is necessary to regularly pay attention to the condition of the vehicle's electrical circuits. Wiring in the engine compartment and around the gearbox is exposed to moisture, dirt and vibration. Periodic inspection of harnesses and connectors will help identify problems early.
Use special silicone connector lubricants to prevent contact oxidation. If you notice traces of moisture in the speed sensor connector, dry it and apply a protective compound. Also monitor the integrity of the wire insulation: if you find any abrasions or cracks, immediately restore the insulation.
It is equally important to monitor the condition of the sensor itself. If you have replaced it before, make sure it is installed tightly and securely. Any play can lead to mechanical wear or contact failure. Regular diagnostics using a scanner will allow you to monitor the sensor parameters and notice deviations in time.
How often should the speed sensor be checked?
It is recommended to check the speed sensor parameters at each scheduled vehicle maintenance, especially if you notice minor jerks when shifting gears. This will allow you to identify the problem before it leads to serious consequences.
Remember that the quality of electrical connections directly affects the operation of the entire vehicle control system. On Nissan Primera P12 this is especially true since electronics play a key role in controlling the transmission. Ignoring minor wiring problems often leads to major breakdowns of expensive components.
FAQ: Frequently asked questions
Is it possible to drive with error code P1720?
It is not recommended to drive with this error. The car will go into emergency mode, which will limit speed and dynamics. In addition, incorrect operation of the gearbox can lead to damage and costly repairs.
How much does it cost to replace a speed sensor on a Nissan Primera P12?
The cost depends on the selected part (original or analogue) and the cost of work. The original usually costs more, but provides greater reliability. Replacement work, as a rule, does not take much time and is inexpensive.
Why does P1720 come back after reset?
This means that the physical cause of the malfunction (wire break, contact oxidation, sensor failure) has not been eliminated. The control unit again detects the absence of a signal and stores the error in memory.
Do I need a scanner to fix error code P1720?
A scanner is required to diagnose and check sensor parameters. It is also required to remove errors and reset adaptations. Without a scanner, you can only visually inspect the wiring, but you will not be able to confirm the serviceability of the system.
Does P1720 affect fuel consumption?
Yes, it does. In emergency mode, the engine operates at higher speeds and the gearbox does not shift gears optimally, which leads to increased fuel consumption and reduced vehicle power.