What Does the Engine Code P0842 Mean?

If your car is showing the P0842 engine code, you’ll need to get your transmission fluid pressure sensor checked out.
Written by Macy Fouse
Reviewed by Melanie Reiff
If your car is showing the P0842 engine code, your transmission fluid pressure sensor has recorded an issue with the transmission fluid or pressure. Be sure to get this looked at quickly as this engine code could also signify bigger issues.
Diagnostic trouble codes (DTCs) help pinpoint issues with your vehicle’s engine. When you get an engine code reading, it’s important to know the meaning of the code so you can find the source and tend to the issue. 
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What does the engine code P0842 mean?

Definition: Transmission Fluid Pressure Sensor / Switch A Circuit Low
The P0842 engine code is a generic code signifying a problem with the transmission fluid pressure sensor/switch (TFPS). This part converts mechanical transmission to an electric signal for control modules. The TFPS is typically attached to the side of the valve within the transmission or screwed to the side of the transmission body.

How much will it cost to fix?

The time to diagnose should take about an hour of labor, which can cost anywhere between $75 and $150 per hour. Depending on the source of the issue, you could have to pay up to $400
In rare cases, you may need a new control module, which may cost up to $1,500.

What can cause the P0842 engine code?

When your car is throwing the P0842 engine code, it often means the TFPS got an unusually high voltage reading
The transmission fluid pressure sensor is intended to control the hydraulic pressure in the transmission and then transmits that data to the engine control module (ECM). It also notifies the computer if there’s any pressure loss.
Other issues that could trigger this engine code include: 
  • Contaminated or low
    transmission fluid
  • Jammed transmission fluid passages
  • Internal transmission failures
  • Faulty ECM

Common symptoms of the P0842 engine code

The signs accompanying this engine code can be obscure or random, other than the
check engine light
being illuminated. Other symptoms may include:
  • Slipping transmission
  • Car is hard to shift
  • Inability to shift
  • Overheating transmission
  • Decreased fuel economy
  • Disengagement from torque converter clutch
Most times the sensor, solenoid, or electric components need replacing. 

How serious is the P0842 engine code? 

Even if symptoms seem mild or unimportant, this code suggests a serious problem that should be dealt with as soon as possible. Your vehicle’s drivability will decrease until it’s undrivable. Leaving it unaddressed could also lead to more expensive repairs in the future.

Can I fix the P0842 engine code myself?

You may be able to repair the P0842 engine code yourself if you have mechanical experience. It’s crucial to correctly diagnose the problem before attempting any repairs, though. 
Depending on the cause of the issue, you may need to: 
  • Replace the pressure control solenoid
  • Refill, flush, or replace old transmission fluid
  • Clearing blocked transmission fluid passage
  • Fixing any mechanical internal transmission failures
  • Replacing the engine control module
It’s a good idea to start with the more common, smaller fixes before moving on to the major parts. And, of course, it’s always best to get a professional inspection to diagnose and repair the issue. 

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