P0993

What it means

P0993 is the generic code for the transmission fluid pressure sensor or switch 'F' circuit reading out of its expected range or performing poorly. The transmission control unit compared the signal from this sensor or switch with the pressure it commanded, or with other inputs such as gear selection and shift solenoid state, and found they did not agree. Which circuit is 'F' and where it sits depends on the transmission, so the exact location must be confirmed for the model.

Symptoms

• Gearbox warning light or malfunction indicator lamp on
• Harsh, delayed or flared gear changes
• Transmission stuck in a single gear (limp mode)
• Slipping under load or when pulling away
• Poor or erratic shift quality when the fluid is hot
• Gear selector position not recognised correctly

Possible causes

• Wiring or connector fault on the sensor or switch circuit (chafing, corrosion, poor pin tension, fluid-soaked connector)likely
• Faulty or drifting transmission fluid pressure sensor or switchlikely
• Incorrect, low, aerated or degraded transmission fluid affecting pressure readingslikely
• Real hydraulic pressure problem, such as a sticking valve body valve, worn pump or leaking seal or clutch circuitpossible
• Faulty shift or pressure control solenoid causing a mismatch between commanded and measured pressurepossible
• Internal harness or valve body wiring fault inside the transmissionpossible
• Transmission control unit fault or outdated software where a known issue exists for the modelrare

How to diagnose

1. Read all stored and pending codes plus freeze frame data, noting gear, fluid temperature, speed and load when the code set, and check for related shift solenoid or ratio codes.
2. Check the transmission fluid level and condition using the manufacturer's procedure, including temperature requirements, and look for leaks, burnt smell, metal debris or foaming.
3. Inspect the sensor or switch, its connector and the wiring to the control unit for damage, corrosion, fluid ingress and poor terminal tension.
4. Identify which sensor or switch is circuit 'F' for the specific transmission from the manufacturer data, as this varies between models.
5. With a scan tool, watch live pressure sensor or switch data against gear selection and commanded pressure, and compare with specification.
6. Check the sensor supply, signal and earth with a multimeter, and test wiring for continuity and shorts.
7. Measure actual line or clutch circuit pressure with a mechanical gauge if the model allows, to separate a sensor fault from a real hydraulic fault.
8. Check for applicable software updates or technical bulletins for the vehicle.

How to fix

• Repair or replace damaged wiring, and clean or replace the faulty connector.
• Replace the pressure sensor or switch if it reads out of range or is erratic and the wiring is sound.
• Correct the fluid level, or replace degraded fluid and filter using the specified fluid type.
• Repair the valve body, replace faulty solenoids, or overhaul the transmission if real pressure loss is confirmed.
• Update the control unit software only if a known fault for this model and fault code is documented, or replace the unit if it is proven faulty.

Can I keep driving?

Nearby codes

• P0992GenericTransmission Fluid Pressure Sensor/Switch F Circuit
• P0994GenericTransmission Fluid Pressure Sensor/Switch F Circuit Low