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Engine Fault Code P0843

Transmission Fluid Pressure Sensor/Switch A Circuit High

Care Engine Code Reader
The Engine Fault Code P0843 refers to an issue with the Transmission Fluid Pressure Sensor or Switch A Circuit. Specifically, it means that the sensor is sending a high voltage signal to the engine control unit (ECU), which indicates that there might be a problem with the transmission fluid pressure.

Heres a breakdown of what this code can mean:

1. Transmission Fluid Pressure Sensor Issue: The sensor itself could be faulty, leading to incorrect readings.

2. Wiring Problems: There could be damaged wiring or poor connections in the circuit that connects the sensor to the ECU.

3. Transmission Fluid Problems: Low or dirty transmission fluid can affect pressure readings, potentially causing this code.

4. Faulty ECU: In rare cases, the engine control unit might have a fault that`s causing it to misinterpret the sensor`s readings.

Manufacturer-Specific Meanings
While P0843 generally indicates the same issue across many vehicles, some manufacturers may have specific interpretations or causes:

Porsche: Similar to the general definition, but may also indicate issues with the PDK (Porsche Doppelkupplung) transmission.

Mini: May relate to specific transmission types used in Mini models, especially those sharing components with BMW.

Mercedes-Benz: Could also indicate issues with the 7G-Tronic transmission, which is sensitive to fluid levels and quality.

Audi: Often linked to the multitronic or S-Tronic transmissions, which have unique pressure specifications.

Jaguar: May indicate issues with the ZF 8-speed transmission, which has specific pressure requirements.

Land Rover: Similar issues can arise in their automatic transmissions, especially in models with adaptive transmission systems.

What to Do Next
If you encounter this code, it`s important to:

1. Check the Transmission Fluid: Ensure its at the correct level and in good condition.

2. Inspect Wiring and Connectors: Look for any signs of damage or corrosion.

3. Test the Sensor: Use a multimeter to check if the sensor is functioning correctly.

4. Scan for Additional Codes: There might be other related codes that can help diagnose the problem.

5. Consult a Professional: If you`re unsure or the problem persists, it`s best to seek help from a qualified mechanic.
The Engine Fault Code P0843 indicates a problem with the Transmission Fluid Pressure Sensor or Switch A Circuit, specifically that the circuit is reading too high. This code can arise from several factors, and while the basic concept is similar across different manufacturers, the specifics can vary. Here are some common causes:

1. Faulty Transmission Fluid Pressure Sensor: The sensor itself may be defective, leading to incorrect readings.

2. Wiring Issues: Damaged or corroded wiring or connectors in the circuit can cause high voltage readings. Look for frayed wires or poor connections.

3. Transmission Fluid Issues: Low or contaminated transmission fluid can affect the sensors performance. Make sure the fluid is at the correct level and in good condition.

4. Faulty Transmission Control Module (TCM): The TCM processes signals from the sensor. If the TCM is malfunctioning, it can misinterpret the readings.

5. Internal Transmission Problems: Issues within the transmission, such as a sticking valve or a problem with the hydraulic system, can lead to incorrect pressure readings.

6. Software Issues: Sometimes, a software glitch in the vehicles control module can cause erroneous codes. An update may be needed.

7. Environmental Factors: Extreme temperatures or moisture can affect the sensors performance.

Manufacturer-Specific Considerations:

Porsche: Look for specific wiring harness issues, as Porsche often uses unique connectors that can corrode.

Mini: Check for common issues with the transmission control unit, as they can sometimes be sensitive to electrical issues.

Mercedes-Benz: Mercedes vehicles often have complex electronic systems; a diagnostic scan may reveal additional codes that can help pinpoint the issue.

Audi: Audi vehicles may have specific recalls or service bulletins related to the transmission system that could be relevant.

Jaguar: Jaguars may have unique sensor designs; ensure the replacement part is compatible with the specific model year.

Land Rover: Land Rover vehicles can be sensitive to software updates, so always check if the latest software is installed.

When diagnosing this code, its essential to perform a thorough inspection of the transmission system and related components. If youre unsure, consulting a professional mechanic with experience in the specific make and model can be beneficial.
The P0843 code indicates a problem with the transmission fluid pressure sensor or switch, specifically that the circuit is reading too high. Heres how you can approach fixing this issue, keeping in mind that the steps may vary slightly based on the manufacturer.

General Steps to Fix P0843:

1. Scan the Vehicle:
– Use an OBD-II scanner to confirm the P0843 code and check for any other related codes. This can help identify if there are multiple issues.

2. Inspect the Wiring:
– Check the wiring and connectors leading to the transmission fluid pressure sensor. Look for any signs of damage, corrosion, or loose connections.

3. Check the Sensor:
– Locate the transmission fluid pressure sensor. Its usually found on or near the transmission. Remove it and inspect for damage or dirt.
– If you have a multimeter, test the sensors resistance according to the manufacturers specifications. If its out of specs, replace the sensor.

4. Inspect Transmission Fluid:
– Check the transmission fluid level and condition. Low or dirty fluid can cause issues. If needed, change the fluid and filter.

5. Clear the Codes:
– After making repairs, clear the codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.

Manufacturer-Specific Considerations:

Porsche:
– For Porsche vehicles, ensure you are using the correct transmission fluid type, as they can be sensitive to fluid specifications.

Mini:
– Mini models often have specific software requirements. After replacing the sensor, a reset of the transmission control module may be necessary.

Mercedes:
– Mercedes vehicles may require the use of STAR Diagnostic tool for proper diagnosis and programming after repairs. Always refer to the service manual for specific procedures.

Audi:
– Audi models may have a more complex transmission system. If the problem persists after replacing the sensor, it may be necessary to check the Transmission Control Module (TCM).

Jaguar:
– On Jaguars, if the sensor replacement does not resolve the issue, a software update for the TCM may be required.

Land Rover:
– For Land Rover vehicles, make sure to check for any software updates or recalls that may relate to the transmission system.


Fixing a P0843 code involves checking the sensor, wiring, and fluid condition. Always refer to the specific service manual for your vehicle model for detailed procedures and specifications. If the problem persists after your repairs, it may be best to consult a professional mechanic.
Driving with a P0843 code, which indicates a problem with the transmission fluid pressure sensor or switch, can be risky. This code means that the sensor is detecting a high voltage or pressure reading, which could lead to several issues. Heres what you need to know:

General Safety Considerations:
1. Transmission Performance: A faulty sensor can cause the transmission to behave erratically, leading to hard shifts or slipping.
2. Potential Damage: Continuing to drive might cause further damage to the transmission, which could lead to costly repairs.
3. Warning Lights: You may see warning lights on your dashboard, indicating a problem that needs attention.

Manufacturer Differences:
Porsche: Generally, it`s advised to avoid driving until the issue is resolved, as it could lead to transmission failure.
Mini: Similar to Porsche, it`s best not to drive with this code, as it can affect the transmission`s performance.
Mercedes: Driving is not recommended, as it could lead to overheating or damage to the transmission.
Audi: Avoid driving until the issue is fixed, as it can cause further complications.
Jaguar: It`s best to get the issue checked out before driving, as it may lead to transmission issues.
Land Rover: Driving with this code can affect the vehicle`s drivability and may lead to more severe problems.


Our view, it is safest to avoid driving your vehicle with a P0843 code. It`s best to have it diagnosed and repaired as soon as possible to prevent further damage. If you must drive, do so cautiously and be aware of any unusual behavior from the transmission.

OBD Codes Explained

Engine Codes

P is for PowerTrain - Engine and Transmission.

P0 Indicates Generic Powertrain Codes

P0 Codes indicate problems with the powertrain and are common for all vehicles using the OBD-II Standard.

P1 Enhanced Manufacturer Specific Codes

P1 Codes are specific to manufacturers.

Sub-System

The 3rd Digit indicates the Sub-System

1 – Emission Management

2 – Injector Circuit

3 – Ignition

4 – Emission Control

5 – Vehicle Speed and Idle

6 – Computer and Output

7 – Transmission

8 – Transmission

9 – Reserved

0 – Reserved

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