P0840 Mercedes-Benz Code - Transmission Fluid Pressure Sensor/Switch 'A' Circuit
Quick Answer
The Transmission Control Module (TCM) monitors the Transmission Fluid Pressure Sensor/Switch signal. Common causes include Faulty Transmission Fluid Pressure Sensor/Switch 'A', Transmission Fluid Pressure Sensor/Switch 'A' harness is open or shorted, Transmission Fluid Pressure Sensor/Switch 'A' poor electrical connection. 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 Mercedes-Benz indicates Transmission Fluid Pressure Sensor/Switch 'A' Circuit.
- Common causes
- Common causes include Faulty Transmission Fluid Pressure Sensor/Switch 'A', Transmission Fluid Pressure Sensor/Switch 'A' harness is open or shorted, Transmission Fluid Pressure Sensor/Switch 'A' poor electrical connection.
- 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.
Code P0840 Mercedes-Benz Description
What are the Possible Causes of the DTC P0840 Mercedes-Benz?
- Faulty Transmission Fluid Pressure Sensor/Switch 'A'
- Transmission Fluid Pressure Sensor/Switch 'A' harness is open or shorted
- Transmission Fluid Pressure Sensor/Switch 'A' poor electrical connection
- Transmission Valve Body
How to Fix the DTC P0840 Mercedes-Benz?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0840 Mercedes-Benz code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
Need more information about the P0840 Mercedes-Benz code?
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Frequently Asked Questions about P0840 Mercedes-Benz Code
1. What does the OBDII code P0840 mean on a Mercedes-Benz?
P0840 refers to a problem with the Transmission Fluid Pressure Sensor/Switch 'A' Circuit, which monitors the transmission fluid pressure to ensure proper operation.
2. What are the common symptoms of code P0840 in a Mercedes-Benz?
Symptoms may include erratic shifting, transmission slipping, delayed gear engagement, reduced fuel efficiency, or the transmission being stuck in limp mode.
3. What causes the P0840 code to appear in a Mercedes-Benz?
Common causes include a faulty transmission fluid pressure sensor, damaged or corroded wiring, low transmission fluid levels, or internal transmission issues.
4. Can driving with a P0840 code damage my Mercedes-Benz?
Yes, driving with this code can lead to further transmission damage if the issue is not addressed promptly.
5. How is the P0840 code diagnosed in a Mercedes-Benz?
A mechanic will use a scan tool to confirm the code, inspect the transmission fluid pressure sensor, check wiring and connections, and analyze the transmission fluid condition.
6. What repairs can fix the P0840 code on a Mercedes-Benz?
Repairs may include replacing the transmission fluid pressure sensor, repairing damaged wiring or connectors, or flushing and refilling the transmission fluid.
7. Can low transmission fluid cause the P0840 code in a Mercedes-Benz?
Yes, insufficient or contaminated transmission fluid can trigger this code by affecting fluid pressure readings.
8. Is the P0840 code covered under warranty for a Mercedes-Benz?
It depends on your vehicle’s warranty coverage, but transmission-related repairs may be covered if the vehicle is still under powertrain warranty.
9. How much does it cost to fix the P0840 code on a Mercedes-Benz?
Repair costs can range from $100 to $500, depending on whether just the sensor needs replacement or there are additional transmission issues.
10. Can I reset the P0840 code without fixing the issue?
You can clear the code with a scan tool, but if the underlying issue is not resolved, the code will likely return and may cause further damage.
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