What it means
The transmission control module detects that pressure control solenoid S 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 S operates a valve that regulates transmission hydraulic pressure. P27D1 sets when the module detects that solenoid S is not performing as expected or is stuck off, so the commanded pressure-control action does not occur; a restricted feed or a spool held closed can cause this condition.
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 check related transmission codes to see when the solenoid S performance fault occurred and which shifts were affected.
- Use scan-tool data to compare commanded solenoid S operation with available transmission pressure or shift-response data.
- Inspect the transmission fluid condition and level using the manufacturer's procedure, since fluid condition can affect hydraulic operation.
- Check the solenoid S connector and wiring for damage or poor contact, while remembering that this is a performance/stuck-off code rather than a specific electrical low or high code.
- Test solenoid S operation and inspect its hydraulic feed for restriction or debris using vehicle-specific service information.
- If the feed is clear but the valve does not move freely, inspect the solenoid S spool and related hydraulic passages for sticking or deposits.
Common fixes
- Correct transmission fluid level or condition if it is outside the manufacturer's requirements.
- Repair a damaged connector or wiring fault affecting solenoid S operation.
- Clear an identified restriction in the solenoid S hydraulic feed.
- Clean or replace solenoid S if its spool is stuck closed or cannot operate freely.
Can I keep driving?
Avoid towing, hard acceleration, and continued driving if the transmission slips or shifts unpredictably. A solenoid S valve stuck off can prevent the expected pressure change, and continued slipping may overheat or damage the transmission.
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.