P0842 Error Code – Symptoms, Diagnosis & Fixes

Most cars, especially those with modern technologies, are fitted with sophisticated computers that help detect faults or any form of malfunction that can lead to costly damages.

The computerized systems of the cars identify these challenges and alert the driver through the dashboard screen. One of the common codes you may likely encounter in your car is P0842.

The code conveys a profound message that you must treat as a matter of urgency before it escalates to a costly fault taking hundreds of dollars. Let’s take a moment to define the P0842 code to understand what it means and how to fix the problem.

Code P0842 Definition

The code – P0842 signifies that the sensor circuit of a car’s transmission fluid pressure is reading an abnormally high voltage.

This sensor circuit’s abnormal high voltage reading is a challenge that must be treated with all seriousness. Though the effects may not be noticeable initially, it can lead to a more complicated problem in the long run.

transmission fluid pressure sensorswitch a circuit low

What Does P0842 Mean?

One of the vital components of a car is the transmission which is responsible for providing the wheels with engine power for motion. It connects to the engine’s back from where it draws power to run.

The shifting of gears and providing torque converter lockup is the responsibility of the transmission. This process is powered by hydraulic pressure, which is controlled by solenoids that are as well controlled by the vehicle’s Powertrain Control Module (PCM).

The vehicle’s PCM is responsible for calculating the degree of pressure at every point in time to enable it to optimize the vehicle’s operations. There is a specific amount of pressure that must not be exceeded.

Therefore, the code P0842 means that your car is experiencing an abnormally high voltage transmission fluid pressure higher than expected.

Once this occurs, the computerized system stores the code immediately. It is essential to note that the Honda P0842 error code is similar to P0842 in Chevy Cobalt.

What Are the Symptoms of Code P0842?

A car rarely breaks down completely without first showing some symptoms for the driver’s awareness. The code P0842 comes with a couple of signs that give a clue about the existence of the challenge. Some of the symptoms include:

  • Check Engine (CE) light display.
  • Slipping transmission or harsh shifting.
  • Defective fuel efficiency.
  • Overheated transmission.
  • Weak shifting ability.
  • Inability to engage or disengage from torque converter clutch.

What Causes Code P0842?

The malfunction code – P0842 is a product of several issues that are related to a vehicle’s transmission. Some of the causes of the P0842 code include the following:

  • Defective electronic pressure control solenoids.
  • Low, contaminated, or dirty transmission fluid.
  • Internal transmission mechanical failure.
  • Blocked flow of transmission fluid.
  • Defective TCM or PCM.

Ensure to properly diagnose the areas outlined above whenever you come across the P0842 code in your vehicle. Correctly identifying the exact cause will help resolve the issue quickly.

How Serious Is Code P0842?

It is possible to manage some mechanical faults over a period without severe consequences; however, this code – P0842 is not one of those faults you should manage over a long period because the consequence can be costly in the long run.

Therefore, it is crucial to treat this issue with every sense of urgency and importance in the initial stage, even before the symptoms become apparent. Quickly approaching the problem will help you avoid risking further costly damage to your vehicle.

Code P0842 Common Diagnosis Mistakes

Most car owners, especially DIYers and sometimes auto mechanics, make a common mistake in addressing the P0842 code issue.

One of the biggest mistakes is to replace the vehicle’s high-pressure pump instead of inspecting the solenoid, sensor, or any other electrical components, to ascertain whether their replacements will solve the problem at once.

Always start by fixing minor faulty components before moving on to the large ones; otherwise, you may end up spending so much only to realize that replacing an insignificant component could have rectified the problem. Patience is necessary when dealing with certain issues.

allison transmission code p0842

Tools Needed to Diagnose Code P0842

Checking, verifying, and fixing the P0842 code fault requires a couple of tools that most DIYers are fond of using. The tools include the following:

  • An OBD II Scanner.
  • A digital volt/ohmmeter – DVOM.

The tools listed above will help reveal the issue when you apply them in diagnosing the fault, especially after observing the P0842 code symptoms. You can make headway with the tools above when diagnosing the code P0842 in GTR as well as in other modern cars.

How to Diagnose Code P0842?

Diagnosing a P0842 code issue will most likely be easy for DIYers who find pleasure in fixing minor faults in their cars. However, if you are not a DIYer, contacting an expert auto mechanic would be best.

In order to appropriately diagnose the code issue, verify the fault with an OBD II Scanner, especially when you notice the symptoms for a while. After that, do the following:

  • Inspect the transmission fluid to ascertain the fluid level or observe for dirt or contaminants.
  • Insect the transmission pressure control solenoid for any faults.
  • Check all transmission-related electrical components to confirm any defects.

Once you identify the real issue with the P0842 code, ensure to fix the problem immediately before it escalates to something more costly.

How do you fix P0842?

Understanding how to fix code P0842 is pretty straightforward after diagnosing the exact cause or causes of the problem. The following approaches will help you fix the code P0842 issue as soon as you discover the fault.

  • Clear off contaminants or deposits blocking the free flow of the car’s transmission fluid.
  • Flush, refill, or replace the vehicle’s old transmission fluid with the manufacturer’s recommended fluid.
  • Get a new replacement for the vehicle’s transmission pressure control solenoid.
  • Repair any electrical or mechanical faults connecting to the transmission system.
  • Replace the faulty TCM or PCM if this is the case.

Final Words

The automotive industry’s technological advancement has helped to overcome the challenge of figuring out problems when you observe the symptoms of a fault in your vehicle.

Ensure always to observe the signals from your car’s computerized systems revealed through the dashboard screen. If you come across the P0842 error code, follow the measures recommended to fix the problem sooner.

It will always be easy for DIYers to fix challenges like this. However, ensure that you understand what you are doing; otherwise, contact an expert auto mechanic to do the job.

Osuagwu Solomon

Osuagwu Solomon is a seasoned automotive technician for the past 9 years, and a technical writer. He loves writing about auto professional repair guides, DIY repair guides, and buyer’s guide. After spending six years in the automotive workshop, he decided to impact his knowledge to people aside his domain, and he has achieved this by centering his Automotive writing skills on REPAIRS.

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