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 reading the pressure of the fluid in the transmission. It's like when you can't tell how much air is in a balloon because the gauge isn't working.
The transmission fluid pressure sensor/switch A is responsible for monitoring the pressure of the transmission fluid. If the sensor or its circuit is malfunctioning, the onboard computer will trigger this code.
The P0840 code is triggered when the Powertrain Control Module (PCM) detects a problem with the transmission fluid pressure sensor/switch 'A' circuit. This sensor is used to monitor the hydraulic pressure in the transmission and ensure it is within the expected range for proper operation.
• Check Engine Light is on
• Transmission may not shift properly
• Poor fuel economy
• Faulty transmission fluid pressure sensor
• Wiring issues such as shorts or open circuits
• Malfunctioning PCM or TCM
PCM: Powertrain Control Module
TCM: Transmission Control Module
• Use an OBD-II scanner to confirm the code
• Inspect the wiring and connectors for damage
• Test the transmission fluid pressure sensor
• Replace the transmission fluid pressure sensor
• Repair or replace damaged wiring/connectors
• Reprogram or replace the PCM/TCM if necessary
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Honda Accord
• Ford F-150
• Chevrolet Silverado
• Regular transmission fluid checks
• Routine maintenance and inspections
• Address wiring issues promptly
Sensor Issue
• Avoid driving the vehicle until repaired to prevent further damage
• Consult a professional mechanic for accurate diagnosis
Check with the vehicle manufacturer for specific warranty coverage related to the transmission system.
This code has been common in vehicles with higher mileage or those that have not had regular transmission maintenance.
Moderate – It is advisable to address this issue soon to avoid potential transmission damage.
Driving with a malfunctioning transmission can be unsafe and may lead to further vehicle damage.
• Vehicle engine running
• Transmission at operating temperature
The transmission fluid pressure sensor is typically located on the transmission housing.
Q: Can I drive with a P0840 code?
A: It's not recommended to drive with this code as it can lead to transmission damage.
Q: How can I reset the P0840 code?
A: The code can be reset using an OBD-II scanner, but it's important to fix the underlying issue first.
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