P0840 Fault Code

Transmission Fluid Pressure Sensor/Switch A Circuit

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

The P0840 fault code indicates an issue with the Transmission Fluid Pressure Sensor/Switch A Circuit. This sensor monitors the fluid pressure within the transmission and helps to ensure that the transmission operates within its optimal range. When this circuit experiences a fault, it can lead to poor transmission performance and increased wear on components.

What are the symptoms of the P0840 code?

Common symptoms associated with the P0840 code may include:

• Erratic shifting or harsh shifts during operation
• Illuminated check engine light on the dashboard
• Transmission overheating due to improper fluid pressure
• Slipping or delayed engagement of gears
• Decreased fuel efficiency due to transmission issues

What causes the P0840 code?

Several factors can lead to a P0840 code, including:

• Faulty transmission fluid pressure sensor
• Wiring issues such as short circuits or open circuits
• Poor electrical connections or corrosion at the sensor or connector
• Low transmission fluid levels or quality
• Malfunctioning transmission control module (TCM)

How to fix P0840?

To resolve a P0840 fault code, the following steps are recommended:

1. Check the transmission fluid level and condition; replace or top off fluid as necessary.
2. Inspect the wiring and connectors related to the transmission fluid pressure sensor for damage or corrosion.
3. Test the sensor to ensure it is functioning correctly and replace it if faulty.
4. Clear the fault code and perform a road test to see if the code returns.
5. If the issue persists, further diagnostics may be required to check the TCM and other related components.