P0843 Code: Transmission Fluid Pressure Sensor / Switch “A” Circuit High

You may use a scan tool to try to figure out what could be wrong with your vehicle. If a P0843 code has been logged, you’ll need to know about its definition, common causes, and common symptoms.

What Does the P0843 Code Mean?

Diagnostic trouble code (DTC) P0843 code stands for Transmission Fluid Sensor/Switch “A” Circuit High. The powertrain control module (PCM) or transmission control module (TCM) triggers the P0843 code if it receives a voltage signal from the transmission fluid pressure switch (TFPS) that doesn’t match the normal operating voltage. This can indicate that there’s an issue with either the TFPS or its circuit. Sometimes, the code can also indicate an internal transmission concern.

The TFPS is responsible for measuring hydraulic pressure inside the transmission, which is important because it gives the PCM some insight into whether the transmission is functioning as it should.

Note: The definition of the P0843 code can be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0843 Code?

There are several things that can trigger the P0843 code including:

• Failed TFPS
• Circuit problems, such as a damaged wire or poor connection
• Failed PCM/TCM

What are the Common Symptoms of the P0843 Code?

The P0843 code can develop the following symptoms:

• Illuminated check engine light
• Transmission doesn’t shift properly
• Vehicle enters limp mode

How to Diagnose the P0843 Code

If a P0843 code has been triggered, you can’t automatically assume that it’s caused by the common causes associated with it. You still need to determine the actual cause before you conduct any repairs. You risk fixing a completely functional component if you skip doing an accurate diagnosis.

The diagnostic process typically involves tests and inspections that might require the use of specialized tools and knowledge. If you find that this might be difficult, then you should reach out to a professional mechanic.

Interested to learn how to diagnose the problem on your own? Watch the video below to get an idea of what the process might involve:

How to Fix the P0843 Code

If you want to fix the problems associated with the P0843 code, then you need to know that there isn’t a single procedure that will guarantee a fix. Vehicle designs can vary greatly from one model to another, so something that works for one vehicle model might not be applicable to another. Your course of action will depend on the diagnosis, which is why getting an accurate diagnosis is important.

It’s best to consult a professional mechanic if you don’t have much experience diagnosing or fixing error codes.