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Engine-Codes – Generic – P0840

P0840 Code - Transmission Fluid Pressure Sensor/Switch 'A' Circuit

Quick Answer

The OBD-II trouble code P0840 indicates a problem with the Transmission Fluid Pressure Sensor/Switch 'A' Circuit. Common causes include Faulty transmission fluid pressure sensor, Damaged wiring or connectors in the sensor circuit, Low transmission fluid levels. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0840 indicates Transmission Fluid Pressure Sensor/Switch 'A' Circuit.
Common causes
Common causes include Faulty transmission fluid pressure sensor, Damaged wiring or connectors in the sensor circuit, Low transmission fluid levels.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P0840 Description

The OBD-II trouble code P0840 indicates a problem with the Transmission Fluid Pressure Sensor/Switch 'A' Circuit. This sensor is responsible for monitoring the hydraulic pressure inside the transmission. The transmission fluid pressure sensor helps regulate the transmission's shifting patterns and ensures smooth operation of the transmission system. When this sensor detects an issue with the transmission fluid pressure, it triggers the P0840 code.

OBDII Code P0840 - Transmission Fluid Pressure Sensor/Switch 'A' Circuit
P0840 Code - Transmission Fluid Pressure Sensor/Switch 'A' Circuit

Common Causes of P0840

  1. Faulty transmission fluid pressure sensor
  2. Damaged wiring or connectors in the sensor circuit
  3. Low transmission fluid levels
  4. Malfunctioning transmission control module
  5. Internal transmission issues

Symptoms of P0840

  1. Erratic shifting patterns
  2. Delayed gear engagement
  3. Harsh or rough shifting
  4. Transmission slipping
  5. Illuminated check engine light

How to Fix P0840

  1. Diagnose the problem by using a scan tool to retrieve the trouble code and inspect the transmission fluid pressure sensor.
  2. Check the wiring and connectors for any signs of damage or corrosion. Repair or replace as needed.
  3. Verify the transmission fluid level and condition. Top off or replace the fluid if necessary.
  4. Test the transmission control module for proper operation and replace if faulty.
  5. Clear the trouble code and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0840

The cost of repairing a Transmission Fluid Pressure Sensor/Switch 'A' Circuit issue can vary depending on the specific cause of the problem and the labor rates in your area. On average, the parts for this repair can range from $50 to $200, while the labor costs can be between $100 and $300. Therefore, the total repair cost can range from $150 to $500. It is recommended to consult with a professional mechanic to get an accurate estimate based on your vehicle's make and model.

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Code P0840 Information for Specific Makes

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0840 Code

1. What are the common symptoms of OBDII code P0840?

- Common symptoms include harsh shifting, transmission slipping, transmission not shifting into gear, and illuminated transmission warning light.

2. What can cause the OBDII code P0840 to trigger?

- The code P0840 is typically triggered by a faulty transmission fluid pressure sensor/switch 'A', wiring issues, low transmission fluid levels, or a malfunctioning transmission control module.

3. How serious is OBDII code P0840?

- OBDII code P0840 can lead to transmission issues and potentially cause further damage if not addressed promptly. It is recommended to have the issue diagnosed and repaired as soon as possible.

4. Can I continue driving with OBDII code P0840 present?

- It is not recommended to continue driving with OBDII code P0840 present, as it can lead to transmission problems and potential safety hazards. It is best to have the issue resolved before driving the vehicle again.

5. How can I diagnose the cause of OBDII code P0840?

- Diagnosis typically involves using a scan tool to check for the code, inspecting the transmission fluid level and condition, testing the transmission fluid pressure sensor/switch 'A', and checking the wiring for any faults.

6. Can I repair OBDII code P0840 myself?

- While some DIY enthusiasts may attempt to repair OBDII code P0840 themselves, it is recommended to have a qualified mechanic diagnose and repair the issue to ensure proper resolution and prevent further damage.

7. What is the typical repair for OBDII code P0840?

- The typical repair for OBDII code P0840 involves replacing the faulty transmission fluid pressure sensor/switch 'A', repairing any wiring issues, topping up or replacing transmission fluid, or addressing any underlying transmission control module problems.

8. How much does it cost to fix OBDII code P0840?

- The cost to fix OBDII code P0840 can vary depending on the cause of the issue, the extent of repairs needed, and labor rates in your area. It is advisable to obtain quotes from different mechanics to compare prices.

9. How long does it take to repair OBDII code P0840?

- The repair time for OBDII code P0840 can vary depending on the complexity of the issue and the availability of parts. In general, it may take a few hours to a day for the repair to be completed.

10. Can OBDII code P0840 be prevented?

- Regular transmission maintenance, such as fluid checks and changes as recommended by the manufacturer, can help prevent issues like OBDII code P0840. Additionally, addressing any transmission problems promptly can help prevent more serious issues from occurring.

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