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P0842 is a diagnostic trouble code (DTC) for "Transmission Fluid Pressure Sensor/Switch A Circuit Low". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
The P0842 code indicates that there has been an abnormally high voltage reading from the transmission fluid pressure sensor circuit. Other shift solenoid, transmission slippage, lock up, gear ratio, or torque converter clutch codes are often stored in the PCM with the P0842 code.
The transmission uses hydraulic pressure, controlled by solenoids, which are controlled by the PCM, to shift gears and provide torque converter lockup. The PCM calculates the necessary amount of pressure at any given time to optimize vehicle operation. If the actual pressure reading is higher than the desired amount of pressure, then the code P0842 will be stored.
The most common cause of the P0842 code is a faulty electronic pressure control solenoid. Other causes can include:
In some cases, only the illumination of the Check Engine lamp will be observed. However, the symptoms of the P0842 code can include:
After verifying the code with an OBD-II scanner, all transmission-related faults should begin with a check of the transmission fluid. If the fluid is too low, it should be refilled; if the fluid is dirty, filled with debris, or smells burnt, it may be that the entire system must be flushed, and then refilled with clean transmission fluid.
After this, or any other repair, is performed, it’s important to clear the code from the PCM, and retest the system, to ensure that no unneeded repairs are performed. If the transmission fluid fix did not cause the code to disappear from the PCM, then next step is to inspect the electrical components, and to continue working through possible repairs until the correct issue is diagnosed.
Most of the time, the biggest error made in diagnosing and repairing the P0842 code is the tendency to replace the high pressure pump, rather than the sensor, solenoid, or the electrical components. It’s important to start with the small and more commonly at-fault items before replacing any major parts when diagnosing the P0842 code.
This code still indicates a serious issue that should be addressed right away, even if serious symptoms are not observed. As time goes on, vehicle performance will decline until the vehicle is not drivable. If this code is not addressed as soon as possible, it could lead to larger and more expensive repairs later on.
In order to address the P0842 code, a mechanic may attempt several repairs, including:
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