P0842 Transmission fluid pressure switch sensor "A" circuit low
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P0842 – OBD-II Trouble Code Technical Description
Trouble code P0842 indicates that the transmission fluid pressure switch sensor A circuit is low.
What does the fault code mean P0842?
Trouble code P0842 indicates that the engine control module (PCM) has received a voltage signal from the transmission fluid pressure sensor that is too low. This may indicate problems with the transmission's hydraulic system, which can cause gears to malfunction and other transmission problems. Other trouble codes may also appear along with the P0842 code related to the shift solenoid valve, transmission slippage, lockup, gear ratio, or torque converter lockup clutch.
Possible reasons
Some possible reasons for the P0842 trouble code:
- Defective transmission fluid pressure sensor: The sensor may be damaged or miscalibrated, resulting in an incorrect pressure reading.
- Problems with wiring or connectors: Poor contacts or breaks in wiring can cause erroneous sensor signals.
- Low Transmission Fluid Level: Insufficient fluid level can cause low system pressure and set a trouble code.
- Transmission hydraulic system problems: Clogged or damaged hydraulic lines, valves, or the transmission pump can cause insufficient system pressure.
- PCM faults: It is rare, but possible, that the problem is due to a fault in the engine control module itself, which is incorrectly interpreting the sensor data.
What are the symptoms of a fault code? P0842?
Symptoms associated with a P0842 trouble code can vary depending on the specific problem in the transmission system, some of the possible symptoms are:
- Gear Shifting Problems: The driver may notice difficulty shifting gears, such as hesitation, jerking, or incorrect shifting.
- Unusual noises or vibrations: Low pressure in the transmission hydraulic system may cause unusual noises or vibrations when the transmission operates.
- Use of a limp mode: The PCM can initiate a limp mode to protect the system from further damage that could limit the functionality of the transmission.
- Increased fuel consumption: Incorrect gear shifting or limp operation of the transmission can lead to increased fuel consumption.
- Check Engine Light Appears: Trouble code P0842 is often accompanied by the check engine light turning on on the instrument panel.
How to diagnose a fault code P0842?
To diagnose DTC P0842, follow these steps:
- Checking Error Codes: Use an OBD-II scanner to check for other error codes in the system. Additional codes may provide additional information about the problem.
- Checking the transmission fluid level: Check the level and condition of the transmission fluid. Low levels or contaminated fluid can cause pressure problems.
- Checking wiring and connectors: Inspect the wiring and connectors connecting the transmission fluid pressure sensor to the PCM. Make sure all connections are secure and there is no damage to the wiring.
- Pressure sensor testing: Test the transmission fluid pressure sensor using a multimeter to ensure it is operating properly.
- Checking the transmission hydraulic system: Check the condition and functionality of the transmission hydraulic system, including valves, pump and hydraulic lines.
- PCM diagnostics: If necessary, perform diagnostics on the engine control module (PCM) to ensure that it is operating properly and that the pressure sensor data is being interpreted correctly.
- Real-time testing: If necessary, perform a real-time transmission system test to observe transmission performance and system pressure.
After diagnosing and identifying the cause of the problem, it is necessary to carry out the necessary repairs or replace faulty components. If you do not have experience in diagnosing and repairing vehicles, it is recommended that you contact a professional auto mechanic for assistance.
Diagnostic errors
When diagnosing DTC P0842, the following errors may occur:
- Faulty pressure sensor diagnosis: The error may be due to incorrect interpretation of data from the transmission fluid pressure sensor. Incorrect testing or incorrect reading of sensor values can lead to incorrect conclusions about sensor performance.
- Skip other problems: Focusing only on the P0842 code may miss other problems in the transmission system, which may be related to shifting, leaks, worn components, etc. Incomplete diagnosis may cause the problem to reoccur in the future.
- Ignoring the physical state of the system: Failure to pay sufficient attention to the condition of the wiring, connectors, pressure sensor and other components of the transmission hydraulic system may result in missing the physical causes of the problem.
- Incorrect repair or replacement of components: Replacing components without adequate diagnosis or repairing without addressing the root of the problem may not solve the problem and result in additional costs and time.
- Incorrect interpretation of scanner data: The error may occur due to incorrect interpretation of the data provided by the scanner. This can lead to incorrect conclusions about the causes and solutions to the problem.
To prevent these errors, it is important to perform a complete and thorough diagnosis, including checking all components of the transmission system and taking into account all available data and factors.
How serious is the fault code? P0842?
Trouble code P0842, indicating that the voltage from the transmission fluid pressure sensor is too low, can be serious because it indicates potential problems in the vehicle's transmission system. Insufficient transmission fluid pressure can cause the transmission to malfunction, which in turn can cause damage to transmission components and even failure.
If the P0842 code is not resolved and ignored, it can cause the following serious consequences:
- Transmission damage: Insufficient transmission fluid pressure can cause wear and damage to transmission components such as clutches, discs and gears.
- Loss of vehicle control: Improper transmission operation may result in loss of vehicle control, which can be dangerous while driving.
- Increased repair costs: Ignoring the problem may cause more serious damage to the transmission and increase the cost of repairs.
Overall, the P0842 code should be taken seriously, and it is recommended to begin diagnosis and repair as soon as possible to avoid more serious problems and additional costs in the future.
What repair will help eliminate the code? P0842?
Troubleshooting trouble code P0842 may include the following steps:
- Replacing the transmission fluid pressure sensor: If the transmission fluid pressure sensor is indeed found to be faulty, it should be replaced with a new, compatible sensor.
- Checking wiring and connectors: The wiring and connectors connecting the sensor to the engine control module (PCM) should be inspected for damage, corrosion, or breaks. If problems are found, the wiring should be replaced or repaired.
- Checking the level and condition of the transmission fluid: Make sure the transmission fluid level is correct and that the fluid is not contaminated or expired. If necessary, replace the transmission fluid.
- Checking the transmission system: Check the condition and operation of other transmission system components, such as hydraulic valves and solenoids, for other potential problems.
- Updating the software: Sometimes the problem may be related to the PCM software. In this case, a software update or reprogramming may be required.
- Repeated Diagnosis: After repairs are made and components are replaced, re-test to ensure the code does not return.
It is important to note that repair measures may vary depending on the specific circumstances and reasons for the P0842 code. If you are unsure of your skills, it is recommended that you contact a professional auto mechanic for diagnosis and repair.
P0842 – Brand-specific information
Trouble code P0842 can apply to various makes and models of cars, several well-known car manufacturers and their trouble code interpretations:
- Volkswagen (VW): Low signal level in the transmission fluid pressure sensor/switch “A” circuit.
- Ford: Transmission Fluid Pressure Sensor/Switch “A” Circuit Low.
- Chevrolet: Low signal level in the transmission fluid pressure sensor/switch “A” circuit.
- Toyota: Transmission Fluid Pressure Sensor/Switch “A” Circuit Low.
- Honda: Pressure sensor in the transmission hydraulic circuit.
- BMW: Transmission Fluid Pressure Sensor/Switch “A” Circuit Low.
- Audi: Transmission hydraulic pressure sensor.
- Mercedes-Benz: Low signal level in the transmission fluid pressure sensor/switch “A” circuit.
Check with your vehicle's specific make and model to get more accurate P0842 code information for your specific situation.
