P0841 is a relatively common fault code. While your Mazda 3’s check engine light comes on, this particular code indicates that there is something wrong with the transmission, specifically the transmission fluid pressure sensor circuit.
It is a generic code, so P0841 has the same definition for any vehicle manufactured after 1996. Before doing anything, check your 3’s transmission fluid.
Abbreviations used in this article:
- PCM– Powertrain control module, is the main computer module with engine and transmission control in a single unit
- TCM– Transmission control module, the TCM controls transmission shifting and is separate from the engine control module. Your Mazda 3 will have a PCM or a TCM. And, for the purposes of this article, they are interchangeable.
- TFPS– Transmission fluid pressure sensor
P0841 Definition: Transmission Fluid Pressure Sensor/Switch “A” Range/Performance
Here is the definition of P0841 for the Mazda 3 broken down into its individual parts
Transmission fluid pressure sensor/switch
The TFPS has two main functions:
- Convert transmission fluid pressure into a signal that the PCM (or TCM) can use to control shifting.
- Verifies that the PCM/TCM transmission shift request has occurred.
Circuit “A” Range/performance
The TFPS converts hydraulic pressure data into a voltage signal that your 3’s TCM/PCM can use to control the transmission. P0841 occurs when this signal is outside the normal operating range for this signal.
P0841 Symptoms: Mazda 3
These are the most common symptoms associated with P0841:
- Limping mode– Your 3 will shift differently and will not have access to all of its gears.
- check engine light– There will often be other codes that occur with P0841. They are usually related to voltage and power.
- Erratic change– Shifts may be smooth (RPM drops slowly during shifting), or they may be too abrupt (RPM drops sharply).
Mazda 3 P0841 Causes + Diagnosis
Diagnosing P0841 on the Mazda 3 can be challenging, due to the location of the TFPS sensor and the wiring associated with it.
1. Check other codes and TSB’s
The first thing you should do is look for other diagnostic codes. They can provide valuable clues about what’s happening within your stream.
TSBs are technical service bulletins. Mazda uses them to fix common and known vehicle problems. Check if there are any related to your problem. You can get them on the NHTSA website.
2. Inspect TFPS wiring
The next thing you are going to want to do is inspect the wiring that goes to the TFPS of your 3. If it is burned or damaged, you will need to replace/repair it.
After that, clear the fault codes from your 3 and see if the P0841.9 comes back.
Whether or not you can access TFPS will determine whether most people can continue to diagnose P0841. TFPS can sometimes be accessed from outside the stream. You may have to open the transmission.
Wiring problems are the most common cause of P0841. Take your time and make sure the harness is in good condition.
3. Other causes
Although a bad TFPS sensor is very likely, make sure the voltage supplied to it is correct and does not change when you move the harness before replacing it.
Diagnosing P0841 is quite simple. The real problem is getting to the wiring and the TFPS. Good luck repairing your 3!