When on your dashboard Nissan Qashqai or Teana The Check Engine light comes on and the diagnostic scanner issues a code. P0745, this is a signal of a serious malfunction in the hydraulic transmission system. This error indicates that the electronic control unit (ECU) cannot correctly control the oil pressure in the automatic transmission, which critically affects the operation of the torque converter and clutches.
Ignoring this problem can lead to complete failure of an expensive machine, since insufficient pressure causes slipping and overheating of the internal elements. You need immediate diagnostic work to determine whether the problem is purely electrical or due to mechanical wear and tear.
Owners of Japanese cars often encounter this error after driving 100,000 kilometers, especially if the oil was changed irregularly. The root cause of P0745 is a failure of the Pressure Control Solenoid A, which stops responding to ECU commands.
The essence of the malfunction and the operation of the hydraulic system
To understand the nature of the code P0745, you need to understand how the hydraulic system of a variator or classic automatic transmission functions on cars Nissan. The ECU constantly monitors the pressure in the line, comparing actual values with calculated values. If the pressure sensor shows a deviation, and a control signal is sent to the solenoid, but there is no reaction, an error is generated.
The pressure solenoid is responsible for regulating the clamping force of the friction discs and the operation of the torque converter lock-up. If it fails, the box goes into emergency mode, limiting torque transmission. This manifests itself in the form of jerks when changing gears or a complete inability to move.
The protection system will prevent you from continuing to drive as normal to prevent catastrophic wear. You need to understand that valve body - this is the heart of the automatic transmission, and any deviations in the operation of its valves require immediate intervention.
Key symptoms and signs of failure
You can recognize a problem with oil pressure not only by the scanner, but also by the car’s behavior on the road. Most often the owners X-Trail and Murano complain of sharp jolts when changing gears, especially when accelerating. The car may jerk as if someone slammed on the brake even though you didn't.
Another telltale sign is loss of power and lack of response when pressing the gas pedal. The car may stall when trying to start or drive at a very low speed without gaining momentum. Sometimes an emergency mode is activated, limiting the transmission to only one or two stages.
- 🚗 Sharp jerks and impacts when changing gears
- 📉 Lack of acceleration and power failures during acceleration
- 🛑 Automatic transition to emergency operation mode of the automatic transmission
- 💡 Check Engine light or automatic transmission fault light comes on
In some cases, increased gearbox noise may be observed due to oil cavitation or pump operation under load. If you notice at least one of these symptoms in combination with an error code, you cannot postpone your visit to the service.
⚠️ Attention: If you feel strong impacts or hear grinding noises while moving, stop immediately. Continuing the trip can lead to destruction of the friction discs and metal shavings in the valve body, which will make repairs many times more expensive.
Common Causes of Code P0745
The causes of errors can be divided into two large groups: electrical and mechanical. Most often the problem lies in the pressure solenoid (Pressure Control Solenoid). Over time, its coil may burn out and the contacts may oxidize, leading to an open circuit or short circuit.
Often the culprit is a contaminated valve body. Thick, old oil or wear products (metal shavings, friction dust) clog thin channels and jam the valve plunger. In this case, the electrical part is OK, but mechanically the valve cannot move.
- ⚡ Failure of the electromagnetic pressure control solenoid
- 🔧 Contamination of the valve body with wear products or old oil
- 🔌 Open circuit or short circuit in the wiring harnesses to the automatic transmission
- 📉 Wear on the transmission oil pump, reducing overall pressure
Less often, but it is still possible that the problem lies in the ECU itself or a malfunction of the oil pressure sensor, which transmits incorrect data about the state of the system. It is important to conduct a comprehensive check to eliminate false positives.
- up to 80,000 km
- 80,000 - 150,000 km
- more than 150,000 km
- Mileage doesn't matter, the car is new
Diagnostics and testing procedure
The first step when a P0745 error appears is computer diagnostics using a professional scanner capable of reading data from the transmission modules. You need to look not only at the code itself, but also at the parameters of the solenoid in real time: voltage, resistance and command from the ECU.
Next, you need to conduct a visual inspection of the wiring harness going to the gearbox. Check the connectors for oxidation, moisture or mechanical damage to the insulation. Often the problem is solved by cleaning the contacts or restoring the integrity of the wiring without replacing parts.
If the electrical part is working properly, the next step is to check the oil pressure with a pressure gauge. Connect the device to the test hole on the valve body and compare the obtained values with the technical specifications for your model Nissan. If the pressure is below normal, the problem may be in the pump or a clogged filter.
☑️ Stages of primary diagnosis
⚠️ Attention: When measuring oil pressure, use only a working pressure gauge with a suitable range. Incorrect connection or excessive pressure can damage the sensors or valve body seals.
In some cases, it is necessary to remove the pan and visually inspect for the presence of metal shavings. If there are chips, this indicates serious wear of the internal elements, and simply replacing the solenoid will not help.
Stages of repair and replacement of components
If diagnostics confirm that the solenoid is faulty, it must be replaced. On most models Nissan The pressure solenoid is located inside the valve body, which requires removing the pan and possibly dismantling the valve body itself. This is a labor-intensive procedure that requires precision.
When replacing the solenoid, it is strongly recommended to flush the valve body and replace the automatic transmission filter, even if it does not look very dirty. Old oil and wear debris can quickly damage a new valve. Use only original oil or a high-quality analogue recommended by the manufacturer.
- 🛠️ Remove the automatic transmission pan and unscrew the hydraulic unit mount
- 🔄 Replace the faulty solenoid with a new original one
- 🧼 Wash the valve body channels with a special cleaner
- 🛢️ Replace the fine filter and fill with fresh oil
After assembling and charging the system, it is necessary to adapt the solenoids through a diagnostic scanner. This is a learning procedure in which the ECU learns new valve characteristics. Without adaptation, the box may not work correctly.