P0990
Universal (All Makes) Vehicle (OBD-II)
Severity: ModerateWhat Does This Error Mean?
P0990 means Transmission Fluid Pressure Sensor 2 Circuit High Input. The second transmission fluid pressure sensor is reading a voltage above the expected range. A high input means either the sensor has failed, the wiring has a short to the positive supply, or there is genuinely excessive hydraulic pressure. Symptoms include harsh shifts, transmission overheating warnings, or poor shift quality.
Affected Models
- Vehicles with dual transmission pressure sensors (Bank 2 or secondary circuit)
- Common in Ford vehicles with 6F35 and 6R80 dual-pressure monitoring systems
- Common in GM vehicles with 6L80 and 8L90 transmissions with multiple pressure sensors
- Common in ZF 8-speed transmissions used in many European and American vehicles
Common Causes
- Failed pressure sensor 2 with an internal short to the signal voltage supply
- Short to B+ voltage in the sensor signal wiring
- Damaged or water-intruded sensor connector causing false high reading
- Genuinely high actual hydraulic pressure from a stuck pressure regulator
- Faulty TCM input circuit reading voltage incorrectly
How to Fix It
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Check the transmission fluid level and condition. Confirm there are no external leaks or signs of overheating.
An overheating transmission can cause abnormal pressure spikes that trigger sensor codes.
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Inspect the pressure sensor 2 connector for corrosion or moisture. Clean with electrical contact cleaner and reseat the connection.
Moisture in the connector is the most common cause of a high voltage reading on pressure sensors.
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Test the sensor signal voltage with a multimeter or scan tool. Normal sensor output is typically 0.5V at low pressure to 4.5V at high pressure.
A reading pinned at 5V (supply voltage) confirms a short to supply or a failed sensor.
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Replace the sensor if it reads 5V regardless of engine state or if it tests outside specification.
Always use a new O-ring or sealing washer when installing the replacement sensor to prevent fluid leaks.
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If the sensor tests normal but the code persists, perform a mechanical pressure test to rule out genuinely high line pressure.
A stuck pressure regulator valve causing over-pressure is a rare but possible cause — a pressure test confirms or rules it out.
When to Call a Professional
Pressure sensor replacement costs $150 to $400. Wiring repair is $150 to $350. If high actual pressure is confirmed, pressure regulator valve service is $400 to $1,000. TCM replacement and programming runs $400 to $900.
Frequently Asked Questions
Can high transmission pressure damage the transmission?
Yes — chronically high line pressure causes excessive clutch apply force. This accelerates clutch pack wear and can burn transmission fluid quickly. Address a high-pressure condition promptly to avoid internal damage.
Is P0990 the same on all vehicles?
The code definition is standardized but the exact sensor location and wiring varies by vehicle. Some vehicles label this sensor as the secondary line pressure sensor. Always use a vehicle-specific service manual to locate the correct sensor.
How do I know if the sensor is bad or the pressure is genuinely high?
A scan tool showing maximum voltage at idle (before pressure builds) indicates a failed sensor or wiring short. If voltage climbs progressively with throttle and engine load, the sensor may be working but detecting real high pressure. A mechanical pressure gauge test confirms actual line pressure.