What it means
The transmission control module detects that pressure control solenoid T is not performing as expected or is stuck off.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Pressure control solenoid T is a valve that controls transmission hydraulic pressure when commanded by the transmission control module. P27D9 sets when the module detects that solenoid T is not responding as expected or is stuck off, so the commanded pressure change may not occur.
Common causes
Most likely first.
- Solenoid spool stuck in closed position
- Hydraulic feed restricted by debris
- Carbon or debris buildup preventing free movement
Symptoms
- Transmission warning light may illuminate
- Harsh or delayed shifting
- Slipping or unexpected shifts
- Transmission may enter limp mode
How to diagnose it
- Record freeze-frame data and transmission live data, including commanded solenoid T operation, before clearing the code.
- Check fluid level and condition using the manufacturer's procedure, since contaminated or incorrect fluid can contribute to restricted hydraulic operation.
- Inspect solenoid T wiring and connector for damage or poor contact, and check for related electrical codes that could affect its command.
- Use the scan tool's supported output controls, if available, to compare commanded solenoid T operation with transmission response.
- If electrical command is present but response remains incorrect, have the solenoid T valve and its hydraulic feed checked for sticking or debris using the manufacturer's procedure.
Common fixes
- Correct the transmission fluid level or condition if it does not meet the manufacturer's requirements.
- Repair a damaged solenoid T connector or wiring fault found during inspection.
- Clean or replace the restricted hydraulic feed or affected valve components if inspection confirms debris.
- Replace pressure control solenoid T if it sticks off or fails its operational test.
Can I keep driving?
Avoid towing, steep climbs, and hard acceleration because slipping or unexpected shifts can worsen if solenoid T cannot regulate pressure. Stop driving if the transmission loses drive or slips severely, and arrange prompt diagnosis.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.