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.
Line Pressure Hydraulic Circuits
Line pressure is controlled by the Line Pressure Control (LPC) solenoid, which is controlled by the PCM. This effects shift feel and apply component operation.
When the engine is running, the pump supplies pressure to the main pressure regulator valve, which is controlled by the LPC solenoid. The main pressure regulator valve controls the line pressure to the LINE circuit which supplies the manual valve solenoid regulator valve and the control pressure regulator valve.
When the manual valve is in the reverse position, it supplies the clutch control bypass valve with line pressure to position it to supply line pressure to the direct (3, 5, R) regulator valve and regulated line pressure to the low/reverse clutch to apply the clutch.
When the manual valve is in the DRIVE or LOW positions, it directs line pressure from the LINE circuit to the DRIVE circuit to supply line pressure to the:
- Clutch control bypass valve
- Forward (1, 2, 3, 4) regulator valve
- Intermediate (2, 6) regulator valve
- Torque Converter Clutch (TCC) regulator valve
- Direct (3, 5, R) clutch regulator valve
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.