P0991 Fault Code

Transmission Fluid Pressure Sensor/Switch E Circuit Intermittent

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0991 fault code refers to an issue with the Transmission Fluid Pressure Sensor/Switch E Circuit. It indicates that there is an intermittent fault within the sensor or the associated circuit, which can affect the transmission's performance and shifting capabilities.

What are the symptoms of the P0991 code?

• The vehicle may experience erratic shifting or hard shifts between gears.
• Check engine light may illuminate, indicating a fault in the transmission system.
• Transmission overheating may occur due to improper fluid pressure readings.
• In some cases, the vehicle may go into limp mode, limiting its driveability.

What causes the P0991 code?

• Wiring issues such as frayed or corroded connections can disrupt the signal.
• A faulty Transmission Fluid Pressure Sensor itself may be causing erroneous readings.
• Problems in the transmission control module (TCM) can lead to improper sensor function.
• Contamination or low fluid levels can impact sensor readings.

How to fix P0991?

• Inspect all wiring and connectors leading to the transmission fluid pressure sensor for damage or corrosion.
• Replace the faulty Transmission Fluid Pressure Sensor if testing indicates malfunctions.
• Ensure proper transmission fluid levels and quality, replacing fluid as necessary.
• Reprogram or replace the transmission control module if it is found to be faulty.