Pressure Control Solenoid A Stuck On
The Powertrain Control Module (PCM) or Transmission Control Module (TCM) has detected that the transmission pressure control solenoid 'A' is stuck in the 'on' position. This means the solenoid is continuously allowing maximum or unregulated hydraulic fluid pressure into the transmission circuits, failing to modulate pressure as commanded.
This code requires immediate attention because driving with unregulated, high transmission line pressure can cause severe internal transmission damage. It can also lead to harsh, jarring shifts that compromise vehicle drivability and safety.
Common symptoms
- Illuminated Check Engine Light
- Extremely harsh or banging gear shifts
- Transmission slipping or failing to engage gears properly
- Decreased fuel economy
- Vehicle entering 'limp mode' (restricted to a single gear)
Likely causes
- Dirty or contaminated transmission fluid
- Defective pressure control solenoid 'A'
- Clogged transmission fluid filter or hydraulic passages
- Damaged or corroded wiring and connectors in the transmission harness
- Internal transmission mechanical failure (e.g., stuck valve body)
- Faulty Transmission Control Module (TCM) or PCM
What to check before replacing parts
Check the transmission fluid level and condition.
Look for: Fluid that is low, burnt, or heavily contaminated with metal shavings, which indicates internal wear or lack of maintenance.
Inspect the transmission wiring harness and connectors.
Look for: Frayed wires, melted insulation, or corroded pins that could cause a short to power or ground, keeping the solenoid energized.
Perform a scan tool bi-directional test on solenoid A.
Look for: An audible click or a change in line pressure readings on the scanner; no change indicates the solenoid is physically stuck or electrically dead.
Test the resistance of pressure control solenoid A with a multimeter.
Look for: Resistance values outside the manufacturer's specified range, indicating an internal short or open circuit in the solenoid coil.
Connect a manual hydraulic pressure gauge to the transmission test port.
Look for: Line pressure that remains constantly high regardless of engine RPM or TCM commands, confirming the solenoid or valve is mechanically stuck open.
This page explains the generic P0747 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.