P0841 Code: What It Is And How To Fix It

Automatic transmissions are amazing, especially those fitted to high-end luxury cars like the Mercedes-Benz S-Class. They are capable of shifting within milliseconds, can handle greater towing loads, have strong gear sets, and make driving a vehicle easy. Today’s automatic transmissions are computer-controlled and loaded with sensors and solenoids. The modern automatic transmissions will rely on these sensors to properly adjust the characteristics of the transmissions dependent upon the environment and load conditions. Like the sensors found throughout an engine, the sensors found in an automatic transmission can fail or have their readings skewed by an internal fault. This can cause the Powertrain Control Module (PCM) to set a Diagnostic Trouble Code (DTC). One code that is often reported along with various transmission faults is the P0841 code, relating to the transmission fluid pressure sensor, which can plague both normal and CVT transmissions. In this article, we’ll cover everything you need to know about the P0841 error code and what to do if your PCM sets this code.

What Does The P0841 Error Code Mean?

The PCM or Transmission Control Module (TCM) will set the P0841 fault code after the specific enabling conditions have been met. For many vehicles, the transmission pressure switches will be monitored constantly by the control module.

Some vehicles use pressure switches and others use pressure sensors. The functions of these are the same.

If the P0841 error code is set, the module has identified improper pressure on one of the pressure switches/hydraulic circuits. The P0841 error code specifically indicates sensor/switch “A” as the issue. This particular sensor/switch is most commonly the lowest mounted or the first mounted sensor/switch viewing the transmission from the input shaft. Of course, we always recommend using a factory service manual to identify the correct location of the relevant sensor/switch.

What Causes The P0841 Code?

The following is a list of the most common causes of the P0841 error code for cars with a conventional automatic or CVT:

• Low transmission fluid level
• Contaminated transmission fluid
• Low main line pressure
• Leaking clutch pack piston
• Cracked or incorrectly installed fluid filter
• Sticking fluid pressure regulator valve
• Valve body check ball incorrectly positioned or damaged
• Faulty wiring or electrical connections
• Faulty pressure sensor/switch
• Faulty valve body
• Faulty PCM/TCM

What Are the Symptoms Of The P0841 Code?

The following are the most common symptoms reported for the P0481 error code:

• Illuminated check engine light
• Failed emissions testing
• Transmission doesn’t shift
• Slipping transmission
• Decrease in fuel economy
• Rough or harsh shifts
• Improperly timed shifts
• Torque Converter Clutch (TCC) does not operate

Can I Still Drive With The P0841 Error Code Present?

Some vehicles may continue driving with the P0841 error code active, while others cannot. This all depends on the severity and cause of the fault code, along with the transmission fail-safe operations. Some vehicles will not be able to accelerate past 20 mph and others may no longer shift. In many cases, the symptoms will worsen over time as a vehicle is driven. Automatic transmissions can be extremely costly to replace or rebuild, so we recommend seeking repairs immediately if this code is set by your vehicle’s computer.

How To Fix The P0841 Error Code

As we listed above, there can be a few causes of the fault code, and issues may be specific to certain models; we covered this code and related codes for the Ram 1500 previously. As always, we recommend verifying the fault code is active before attempting any repairs. To verify the fault code is active, you’ll need your vehicle’s PCM/TCM scanned. These scans can be performed for free by most local parts stores or by any automotive repair facility. Once your vehicle’s On-Board Diagnostic System (OBD-II) has been scanned, we recommend taking note of any other DTCs as they can be related to the fault. If you’ve verified the P0841 code is present, you can begin diagnosing/repairing the issue. Below, we will cover the most common repairs for the P0841 fault code.

Assessing Fluid Level And Condition

We’ve talked about the importance of checking transmission fluid in previous articles and videos. However, being that it is a simple issue, it’s often overlooked by many people and repair technicians. When it comes to automatic transmission issues, you should always verify the fluid level and condition first. Remember to keep your vehicle positioned on a level surface, follow the manufacturer steps, adhere to maintenance interval tables, and always use the correct fluid when topping off. Additionally, if your vehicle is due for new transmission fluid, we recommend having the system flushed.

If the transmission fluid is severely burnt or contaminated, severe internal transmission wear may have occurred. In this scenario, replacing the transmission fluid will likely only worsen symptoms.

Clogged Or Damaged Transmission Fluid Filter

Years ago, it was commonplace to service a transmission fluid filter. Today, these services are often forgotten about. If your vehicle has light-brown colored transmission fluid, we recommend freshening up your transmission with a new fluid filter and fluid.

When removing a transmission filter and draining the fluid, only about 40% of the fluid will be removed. This is why we recommend a fluid flush.

Faulty Pressure Sensor/Switch

On some vehicles, inspecting the transmission pressure sensor/switch can be done with a multimeter. To do this, you’ll need to identify the location of the transmission fluid pressure sensor/switch ‘A’. On most vehicles equipped with transaxles, the sensor/switch can be found on the underside of the transaxle. On vehicles equipped with a transmission, it can be found on the side of it. Once located, inspect the sensor and wiring. Loose or corroded connector terminals can cause the error code to be set. Test the circuit wiring with a multimeter according to the service manual. Replacing a sensor is typically done by removing the fastener or unthreading the sensor from the transmission housing.

Internal Transmission Failures

Once the sensor/switch and fluid have been verified, if the P0841 code is still present, it’s possible internal repairs will be needed. In some cases, this can lead to entire transmission replacements or overhauls. We recommend taking your vehicle to a transmission specialist or dealership for these repairs.

How Much Does It Cost To Fix The P0841 Error Code?

The specific or exact cost to repair the P0841 error code will vary by the specific fault, make, and model of the vehicle affected. In the case of a P0841 code on a Nissan Altima, the typical repair is a fluid flush and filter change. RepairPal estimates this costs around $200 on this model, but as much as $500 on other models. For the P0841 code on Dodge vehicles, the most common repair is a sensor replacement, if not a fluid and filter change. We used AllData’s Find-A-Fix and NAPA ProLink to generate an average cost estimate. The cost will likely come to around $150 – $300 if you let a shop handle the repairs. If you perform this repair yourself, you can expect to pay between $50 and $150. For transmission replacements and/or a transmission overhaul, RepairPal estimates the cost to replace this will be around $5,500 – $6,000.

The P0841 error code is one that can range from a minor or simple repair to an expensive major repair such as a transmission replacement. We recommend you pay close attention to the symptoms your vehicle exhibits, along with your transmission fluid level and condition. Improper fluid levels and conditions are the most common cause of the P0841 error code and can easily be remedied by most DIYers. If you’ve checked the simple issues first and your vehicle continues to set the P0841 error code, we recommend you seek the help of the pros as it’s not an issue you want to continue driving with.