Wiring fault in the sensor or switch circuit, such as a signal wire shorted to voltage or a damaged harness; Corroded, loose or contaminated connector at the sensor, valve body or TCM; Faulty fluid pressure sensor or switch reading high or stuck; Incorrect hydraulic pressure caused by a stuck valve, worn solenoid or internal leak; Low, degraded or contaminated transmission fluid, or a blocked filter; Open circuit on the sensor ground or reference supply problem; Faulty transmission control module or outdated software where a known fault exists.

P0990

Transmission Fluid Pressure Sensor/Switch E Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
9: AreaTransmission
90: FaultThe specific fault in that area

What it means

P0990 means the transmission control module has detected a high voltage or high signal condition in the circuit for transmission fluid pressure sensor or switch 'E'. The signal sits above the expected range, or does not agree with the pressure the TCM is commanding. Which sensor or switch is 'E', and where it sits in the valve body or case, depends on the make, model and transmission.

Symptoms

Gearbox warning light or malfunction indicator lamp on
Gearbox in limp mode, often stuck in one gear
Harsh, delayed or flared gear changes
Slipping or loss of drive in certain gears
Poor fuel economy
Gearbox will not shift into some ratios or locks out manual shifting

Possible causes

Wiring fault in the sensor or switch circuit, such as a signal wire shorted to voltage or a damaged harnesslikely
Corroded, loose or contaminated connector at the sensor, valve body or TCMlikely
Faulty fluid pressure sensor or switch reading high or stucklikely
Incorrect hydraulic pressure caused by a stuck valve, worn solenoid or internal leakpossible
Low, degraded or contaminated transmission fluid, or a blocked filterpossible
Open circuit on the sensor ground or reference supply problempossible
Faulty transmission control module or outdated software where a known fault existsrare

How to diagnose

Read all stored codes and freeze frame data, noting gear, fluid temperature and vehicle speed when the fault set, and check for related pressure or solenoid codes
Check the transmission fluid level and condition, following the manufacturer procedure for the model, as some are sealed units
Inspect the wiring harness and connectors between the gearbox and TCM for chafing, fluid ingress, corrosion and bent or pushed-out pins
View live data for the sensor or switch signal and compare it with the specified value at rest and while shifting
Check the sensor reference voltage, ground and signal at the connector with a multimeter against the manufacturer wiring diagram
Test the wiring for a short to voltage or an open circuit, with the connectors unplugged
Check for manufacturer technical bulletins or software updates relevant to the model and gearbox
If the electrical side is sound, carry out hydraulic pressure tests and valve body inspection as the manufacturer specifies

How to fix

Repair or replace damaged wiring and fix any short to voltage or open circuit
Clean, repair or replace corroded or damaged connectors and terminals
Replace the faulty pressure sensor or switch
Correct the fluid level, or change degraded fluid and filter using the specified fluid
Repair or replace the valve body, solenoids or other worn hydraulic components if pressure is incorrect
Update or replace the TCM only when a fault or outdated software is confirmed

Can I keep driving?

Medium severity

The car may be driveable in limp mode, but shifting can be harsh and continued use risks internal gearbox wear. Get it diagnosed soon and avoid towing or heavy loads until it is fixed.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.