Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is having trouble getting a steady signal from a part that checks the pressure of the transmission fluid. It's like when a light bulb flickers on and off because of a loose wire.
The P0991 code is triggered when the transmission control module (TCM) detects an intermittent signal from the transmission fluid pressure sensor/switch E circuit.
The transmission fluid pressure sensor/switch E is responsible for monitoring the pressure of the transmission fluid. This information is used by the TCM to ensure proper transmission operation. An intermittent circuit can cause erratic transmission behavior or incorrect pressure readings.
• Check Engine Light is on
• Erratic or harsh shifting
• Transmission slipping
• Faulty transmission fluid pressure sensor/switch
• Wiring issues such as frayed or damaged wires
• Poor electrical connection in the sensor circuit
Transmission Control Module (TCM): A computer that controls the operation of the transmission.
OBD-II: On-Board Diagnostics, a standardized system in vehicles for self-diagnosing and reporting.
• Use an OBD-II scanner to verify the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the transmission fluid pressure sensor/switch for proper operation.
• Replace the faulty transmission fluid pressure sensor/switch.
• Repair or replace damaged wiring or connectors.
• Clear the code and test drive to ensure the issue is resolved.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regularly inspect and maintain transmission fluid levels.
• Check and replace transmission fluid as recommended by the manufacturer.
• Ensure electrical connections are secure and free of corrosion.
Sensor Issue
• If you notice transmission issues, have the vehicle inspected promptly.
• Avoid driving aggressively until the issue is resolved.
Check if your vehicle's powertrain warranty covers transmission components.
This code has been associated with intermittent transmission issues in vehicles with electronic transmission controls.
Moderate – It should be addressed soon to prevent potential transmission damage.
Ignoring this issue could lead to further transmission damage, potentially causing unsafe driving conditions.
• Vehicle at operating temperature
• Transmission in various gears
The transmission fluid pressure sensor/switch is typically located on the transmission housing.
Q: Can I drive with a P0991 code?
A: It's possible, but not recommended. Driving with this code can lead to transmission damage.
Q: How do I reset the P0991 code?
A: After repairs, use an OBD-II scanner to clear the code. If the issue is fixed, the code should not return.
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