Pressure Control Solenoid A Intermittent
The P0749 code indicates that the Powertrain Control Module (PCM) or Transmission Control Module (TCM) has detected an intermittent electrical issue or erratic voltage reading in the transmission pressure control solenoid 'A' control circuit. This solenoid regulates hydraulic pressure for shifting, and an intermittent signal means the computer cannot reliably control transmission line pressure.
An intermittent pressure control solenoid issue should be diagnosed promptly to prevent erratic shifting. Ignoring it over time can lead to internal transmission damage due to incorrect hydraulic line pressure.
Common symptoms
- Illuminated Check Engine Light
- Harsh or erratic transmission shifting
- Transmission slipping between gears
- Transmission entering 'limp mode' (stuck in a single gear)
- Decreased fuel economy
Likely causes
- Low or dirty transmission fluid
- Loose, corroded, or damaged wiring and connectors in the solenoid circuit
- Faulty transmission pressure control solenoid 'A'
- Blocked internal transmission fluid passages
- Faulty Transmission Control Module (TCM) or PCM
What to check before replacing parts
Check the transmission fluid level and condition.
Look for: Low fluid levels or burnt, dirty fluid which can cause erratic hydraulic pressure and intermittent solenoid operation.
Inspect the wiring harness and connectors for the transmission and solenoid 'A'.
Look for: Loose connections, frayed wires, or corrosion that would cause an intermittent electrical connection.
Test the pressure control solenoid 'A' resistance with a multimeter.
Look for: Resistance values outside the manufacturer's specified range, or fluctuations when tapping the solenoid lightly, indicating an internal intermittent fault.
Check the solenoid circuit for continuity and ground.
Look for: Intermittent open or short circuits between the TCM and the transmission connector while gently wiggling the wiring harness.
Perform a transmission line pressure test using a mechanical gauge.
Look for: Erratic or out-of-spec hydraulic pressure readings that confirm the solenoid is failing to regulate pressure properly.
This page explains the generic P0749 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.
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