Transmission Fluid Pressure Sensor/Switch "E" Circuit High
The P0990 code indicates that the Powertrain Control Module (PCM) or Transmission Control Module (TCM) has detected an abnormally high voltage signal from the Transmission Fluid Pressure (TFP) Sensor/Switch 'E' circuit. This means the sensor is reporting a fluid pressure value that exceeds the maximum expected threshold for the current operating conditions.
While the vehicle may still be drivable, prolonged driving with incorrect transmission pressure readings can lead to harsh shifting and internal transmission damage. It should be diagnosed and repaired as soon as possible to prevent costly repairs.
Common symptoms
- Illuminated Check Engine Light (MIL)
- Harsh or erratic transmission shifting
- Transmission slipping between gears
- Vehicle stuck in 'limp mode' (restricted to a single gear)
- Decreased fuel efficiency
Likely causes
- Defective Transmission Fluid Pressure Sensor/Switch 'E'
- Damaged, corroded, or shorted wiring in the sensor 'E' circuit
- Poor electrical connection at the sensor or TCM connector
- Dirty or contaminated transmission fluid causing blockages
- Internal transmission mechanical or valve body failure
- Faulty Transmission Control Module (TCM) or PCM (rare)
What to check before replacing parts
Check transmission fluid level and condition.
Look for: Fluid that is low, burnt, or heavily contaminated, which can affect pressure readings and sensor operation.
Visually inspect the wiring harness and connector for Sensor 'E'.
Look for: Frayed wires, melted insulation, or corroded pins that could cause a short to voltage.
Scan for other related transmission codes.
Look for: Additional codes that might indicate a broader electrical issue, valve body problem, or multiple sensor failures.
Test the sensor 'E' circuit voltage with a digital multimeter.
Look for: Voltage readings at the sensor connector that exceed the manufacturer's specified reference voltage (usually 5V), indicating a short to power.
Monitor live data for the TFP Sensor 'E' using an advanced scan tool.
Look for: The pressure reading remaining fixed at a maximum value regardless of actual transmission operation or gear selection.
This page explains the generic P0990 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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