What it means
The control module detects a range or performance problem in the transmission fluid pressure sensor/switch F circuit.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Transmission fluid pressure sensor/switch F provides pressure feedback that the control module compares with expected transmission conditions. P0993 sets when the F circuit's reading or response is outside the expected range; a sensor, wiring fault, or actual pressure problem may be involved.
Common causes
Most likely first.
- Faulty pressure sensor/switch F
- Open, shorted, or high-resistance wiring or connection
- Transmission fluid pressure outside the expected range
- Control module fault
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and compare pressure sensor/switch F live data with commanded gear and operating conditions to see when it falls outside the expected range.
- Inspect the F sensor connector and harness for corrosion, loose pins, fluid contamination, opens, shorts, or chafing.
- Check transmission fluid level and condition using the manufacturer's procedure because abnormal fluid condition or level can accompany pressure problems.
- Test the F sensor reference, ground, and signal circuit, and compare sensor response with the manufacturer's specification.
- If the electrical circuit passes, check actual transmission pressure using the manufacturer's specified method before replacing the sensor or suspecting the control module.
Common fixes
- Repair loose, corroded, or damaged F sensor wiring and connector terminals.
- Correct fluid level or condition using the specified fluid and service procedure.
- Replace pressure sensor/switch F if its output fails the manufacturer's tests.
- Repair an internal hydraulic pressure problem if measured pressure is outside specification.
- Address a control-module fault only after the F sensor, wiring, and pressure checks pass.
Can I keep driving?
Avoid towing, steep climbs, and hard acceleration if shifting is abnormal; use only a short, gentle trip for diagnosis if the transmission still engages reliably. Slipping or repeated harsh shifts can quickly add wear, so stop if drive is lost or shifts become unpredictable.
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.