Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSINFINITI2002Q45 V8-4.5L (VK45DE)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTTRANSMISSION CONTROL SYSTEMSDESCRIPTION AND OPERATIONLINE PRESSURE CONTROL
2002 Infiniti Q45 V8-4.5L (VK45DE)
Line Pressure Control
2002 Infiniti Q45 V8-4.5L (VK45DE)SECTION Line Pressure Control
Line Pressure Control
- When an input torque signal equivalent to the engine drive force is sent from the ECM to the TCM, the TCM controls the line pressure solenoid.
- This line pressure solenoid controls the pressure regulator valve as the signal pressure and adjusts the pressure of the operating oil discharged from the oil pump to the line pressure most appropriate to the driving state.
LINE PRESSURE CONTROL IS BASED ON THE TCM LINE PRESSURE CHARACTERISTIC PATTERN
- The TCM has stored in memory a number of patterns for the optimum line pressure characteristic for the driving state.
- In order to obtain the line pressure characteristic that the TCM has selected as being the most appropriate characteristic in the current driving state, the TCM controls the line pressure solenoid current value and thus controls the line pressure.
Normal Control
Each clutch is adjusted to the necessary pressure to match the engine drive force.
Back-up Control (Engine brake)
When the select operation is executed during driving and the transmission is shifted down, the line pressure is set according to the vehicle speed.
During Shift Change
The necessary and adequate line pressure for speed change is set. Therefore, the line pressure characteristic is set according to the input torque and speed change type.
At Low Fluid Temperature
When the A/T fluid temperature drops below the prescribed temperature, in order to speed up the action of each friction element, the line pressure is set higher than the normal line pressure characteristic.
- When an input torque signal equivalent to the engine drive force is sent from the ECM to the TCM, the TCM controls the line pressure solenoid.
- This line pressure solenoid controls the pressure regulator valve as the signal pressure and adjusts the pressure of the operating oil discharged from the oil pump to the line pressure most appropriate to the driving state.
LINE PRESSURE CONTROL IS BASED ON THE TCM LINE PRESSURE CHARACTERISTIC PATTERN
- The TCM has stored in memory a number of patterns for the optimum line pressure characteristic for the driving state.
- In order to obtain the line pressure characteristic that the TCM has selected as being the most appropriate characteristic in the current driving state, the TCM controls the line pressure solenoid current value and thus controls the line pressure.
Normal Control
Each clutch is adjusted to the necessary pressure to match the engine drive force.
Back-up Control (Engine brake)
When the select operation is executed during driving and the transmission is shifted down, the line pressure is set according to the vehicle speed.
During Shift Change
The necessary and adequate line pressure for speed change is set. Therefore, the line pressure characteristic is set according to the input torque and speed change type.
At Low Fluid Temperature
When the A/T fluid temperature drops below the prescribed temperature, in order to speed up the action of each friction element, the line pressure is set higher than the normal line pressure characteristic.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.