For most motorists, an engine warning light illuminated on the instrument cluster is quite unnerving, frustrating, and troubling. After all, such a warning light connotes engine failure that may drop an expensive repair bill on the table. Not just the repair bill. If this light is ignored sometimes, it’ll cause total engine damage.
We sometimes associate this light with severe mechanical issues on drivetrain and powertrain components, which are not always true. Some check engine light causes are far less problematic than you may think. Others can be moderate and severe depending on the actual cause. A perfect example is the P0846 error code. This error code can be problematic as it can cause a vehicle to be inoperable.
When talking of diagnostic trouble codes, P0846 can pose a potential drivability problem for the driver. However, depending on the cause, it can be fixed by just topping the transmission fluid.
This article will discuss the meaning, causes, symptoms, diagnostics mistakes, diagnoses, and fixes.
Code P0846 Definition
Transmission Fluid Pressure Sensor/Switch B Circuit Range/Performance.
P0846 means the car computer has detected a malfunction relating to the transmission fluid pressure switch.
What Does P0846 Mean?
Diagnostic trouble code P0846 is a generic fault code, which means the TCM or PCM on all newer cars with OBD-II can register it when they sense abnormality in the transmission fluid pressure. This includes Chrysler, Dodge, Honda, Nissan, Toyota, GMC, and Chevrolet. This code is common with Nissan cars.
The transmission fluid pressure switch is connected to the transmission valve inside the tranny unit. Some automakers screw it to the transmission body itself.
Remember, the transmission fluid pressure switch (TFPS) helps convert mechanical transmission into an electrical signal. This helps the transmission control module and powertrain control module to understand what’s goes on in the TFPS. Once the electrical signal gets to the PCM, it’ll inform other switches and regulators using the car’s data communication bus.
The powertrain control module registers diagnostics trouble code [DTC] P0846 when it notices aberrant transmission fluid reading. The transmission system works with a hydraulic system to monitor and regulate essential tranny features like gearshift actuation and torque converter lockup.
If the transmission control module [TCM] or powertrain control module [PCM receives an anomalous signal from the transmission fluid pressure switch, it’ll log on P0846 code.
What Are The Symptoms Of Code P0846?
Code P0846 will display several signs to notify the driver of an imminent problem that needs attention. These symptoms include;
- Check engine light
- Erratic or hard gear shifts
- Transmission slipping
- Overheating transmission
- Bad gas mileage
- Vehicle starts in second or third gear
- Loss of shifting ability
- Lack of engagement and disengagement from torque converter clutch.
Code P0846 Jeep symptoms and P0846 Nissan Juke are the same. As a generic error code, these symptoms can appear on any vehicle model. If you notice two or more of these symptoms on your car, you most likely have an aberrant transmission fluid pressure.
What Cause of Code P0846?
The causes of P0846 on a dodge or any vehicle model do not appear in seclusion. Several issues can cause this single problem. The severity of the problem and the repair rely on the actual cause. These are the causes you should look into when diagnosing;
- Inadequate transmission fluid
- Transmission fluid leak
- Dirty transmission fluid
- Burnt or frayed wiring harness and connectors
- Hydraulic pressure issues
- Defective pressure regulator
- Lousy pressure control solenoid
- Faulty torque converter
- Transmission fluid pressure sensor
- Bad transmission pump
- Valve body issues
- Damaged transmission control module [TCM] or powertrain control module [PCM].
Since there are many potential causes of the P0846 error code, it can be a complex repair job.
How Serious Is Code P0846?
The severity of fault code P0846 can be moderate or severe. In moderate cases, you experience harsh gear shifting, reduced gas mileage, overheating transmission, and check engine light.
In worse cases, it can render your vehicle inoperable. The moment the car computer logs P0846, it will trigger an engine warning light on the instrument cluster.
Code P0846 Common Diagnosis Mistakes
When diagnosing and tracing vehicles’ faults, technicians and DIYers should start from minor components to significant parts. The reason is to avoid replacing expensive components unnecessarily.
The most common mistake mechanics make when diagnosing P0846 Nissan Sentra and other vehicle models is overlooking minor probable causes.
You should start with transmission fluid, wiring, circuitry, transmission fluid pressure sensor, hydraulic blockages before heading to significant components like transmission valve body and transmission pressure pump.
Tools Needed to Diagnose Code P0846
Here are the tools needed to fix P0846 trouble codes;
- Digital multimeter
- Vehicle-specific diagnostics information booklet
- OBD-II scan tool
- DVOM (digital volt/ohmmeter).
How to Diagnose Code P0846
Scan the vehicle with an OBD-II scan tool. Pull all the registered codes and start with the related power codes logged along with P0846. If there are other related TFPS codes, note them as they could be the reason behind P0846.
Locate the TFPS and inspect the wiring and the circuitries. The switch is usually connected to the transmission unit itself. Inspect the wires and circuits by checking burnt wires, scrapping, rubbing, melting plastic, etc.
Invest your time and check the connectors on the switch socket. Check for rust and corrosion and clean it if needed. This is common with sensors mounted on the transmission body. You can clean the connectors with a plastic bristle brush and electrical contact cleaner. Allow it to dry, and then apply electrical grease to the metal points.
Erase the trouble codes from the car computer with a scan tool. Re-scan the car and see if the code will reappear. If it doesn’t, the problem is from the wiring connectors.
If the trouble code appears again, test the transmission fluid pressure switch. Turn off the vehicle and remove the key. Disconnect all electrical connections that lead to the TFPS.
Connect the black lead of the digital voltmeter on the low reference terminal of the transmission fluid pressure switch connector. Connect the red lead to the TFPS wiring harness connector.
Insert the key and turn the ignition to the ON position. Your voltmeter should read 12v or 15v. Check vehicle-specific repair manuals for the exact specifications.
Wiggle the lead wire and see if the reading will change. If the voltmeter displays the incorrect reading, you have a lousy ground or power connection that needs replacement. It may require changing the TCM/PCM.
If the sensor and wiring harness passed the volt test, test the pressure resistance. Connect the red voltmeter red lead to the TFPS signal terminal, and the black lead to low interference terminal or ground. Check if the pressure resistance reading on the sensor aligns with the manufacturer’s specifications.
While monitoring the resistance readings on the DVOM, wiggle the connections. If it cuts off the reading, you’ll need to replace the transmission fluid pressure sensor.
If the car passes the voltage and resistance test and the trouble code is still present on the car computer, you have a defective TFPS switch. Internal system components failures and TCM/PCM inspection should wait until you replace the lousy TFPS switch.
If you don’t trust your guts to follow the steps above or are still wondering what to do, contact an ASE-certified mechanic for a professional diagnosis and repair.
How Do You Fix P0846?
Here are the repair procedures to fix P0846 fault codes.
- Replace faulty connectors and wires
- Cleaning of corroded TFPS switch connectors
- Replacement of pressure control solenoid
- Unclogging blockages on transmission fluid passages
- Refilling, flushing, or replacement of old transmission fluid
- Replacement of faulty TFPS
- Replacement of lousy PCM/TCM.
This article has provided answers to the meaning, symptoms, causes, diagnoses, and how to fix error code P0846.
As alluded to above, the severity of the symptoms and problems of P0846 rely on the failed component. If the code appears because of electrical failures, the TCM/PCM can indemnify to a certain degree.
Remember, if the PCM/TCM is the culprit, reprogram it after replacement.