What the P0842 Allison Transmission Code Means and How to Fix It

AvatarByCarl Frisch

P0842 is a transmission diagnostic trouble code (DTC) for Allison transmissions. It indicates an issue with the transmission’s pressure control solenoid. The pressure control solenoid regulates the amount of oil pressure within the transmission system. When this code is present, it means that the vehicle has detected a difference in the expected and actual oil pressure, which can cause problems with shifting or other transmission-related issues. To resolve this issue, it may be necessary to replace the pressure control solenoid or clean and inspect it for any signs of damage or wear. In some cases, a software update may need to be performed as well.

Understanding and Troubleshooting the P0842 Allison Transmission Code

Many drivers have experienced the dreaded P0842 error code for their Allison transmission. This code indicates a problem with the transmission control module, which can be caused by wiring issues, mechanical problems, or software glitches. To avoid further issues with your Allison transmission, it is important to understand the P0842 code, diagnose and troubleshoot it properly.

Understanding the P0842 Code

The P0842 error code is an indication of an issue with the transmission control module (TCM). This component of the vehicle’s transmission system is responsible for controlling gear shifting and other related functions. When this module malfunctions, drivers may experience difficulty shifting gears or their check engine light may become illuminated.

Diagnosing the P0842 Code

To properly diagnose a P0842 error code, it is important to inspect all components of the vehicle’s electrical system. This includes checking for loose wires or connectors that could be causing a disruption in power flow. Additionally, mechanics will need to examine all mechanical components of the transmission system to ensure that everything is working properly. Lastly, any software glitches should be addressed in order to prevent further issues from occurring.

Troubleshooting the P0842 Code

Once any potential issues have been identified and diagnosed, mechanics can then begin troubleshooting them accordingly. In most cases, this means replacing faulty wiring harnesses or connectors as well as repairing any damaged mechanical components of the transmission system. Additionally, technicians may need to update software settings in order to prevent further problems from occurring in the future.

Common Causes of a P0842 Code

When diagnosing a P0842 error code, mechanics need to consider several potential causes such as wiring issues, mechanical problems, and software glitches. Wiring issues can arise when loose connections or broken wires disrupt power flow between components of the vehicle’s electrical system. Mechanical problems can occur due to wear and tear on parts such as gears or clutches which can cause difficulty when shifting gears or other related functions. Lastly, software glitches can also disrupt proper operation of certain systems within a vehicle’s transmission system leading to an error code being displayed on dashboard monitors.

Tips for Avoiding Further Problems with the Allison Transmission

In order to ensure your Allison transmission remains in good working condition for years to come it is important that regular maintenance checks are performed on all components of your vehicle’s electrical and mechanical systems as well as prompt repairs being made whenever necessary. Additionally, ensuring all software settings are up-to-date can help prevent further complications from occurring within your vehicle’s transmission system due to outdated settings or programming errors which could lead to additional errors codes being displayed on dashboard monitors in future instances.

Parts Needed To Repair A P0842 Error Code

If you are experiencing difficulties with your Allison transmission due to a potentially faulty TCM then you will likely need some new parts such as wiring harnesses and connectors in order for repairs to be made effectively and efficiently without compromising safety features within your vehicle’s transmission system . It is important that you purchase original parts from reputable suppliers so that you know they will fit correctly and provide reliable performance when operating your vehicle on public roads .

Common Symptoms Of An Allison Transmission P0842 Error Code


When diagnosing an issue with an Allison Transmission due to a potentially faulty TCM then some common symptoms which drivers may experience include difficulty shifting gears or illumination of their check engine light . If either of these symptoms occur then it is important that you seek out professional assistance immediately so that any underlying issues can be identified quickly before they become more serious .

How to Reset the Allison Transmission After Fixing a P0842 Error Code

Resetting the Allison transmission after fixing a P0842 error code is relatively straightforward. First, you need to turn off your vehicle and disconnect the battery. Then, you should locate the transmission control module (TCM), which is usually found near the front of your vehicle. Once you have found it, remove the TCM and use a scan tool to erase any stored codes. Finally, re-install the TCM and reconnect your battery. Afterward, start up your vehicle and check that the error codes have been cleared.

Cost of Repairing an Allison Transmission with a P0842 Error Code

The cost of repairing an Allison transmission with a P0842 error code can vary depending on several factors, such as labor costs, parts costs and diagnosis fees. Generally speaking, it can range anywhere from $200 to $1,000 or more. It’s important to note that if you opt for professional service rather than attempting a DIY repair job yourself, you may incur additional costs for diagnostic services in addition to any parts or labor required for repair work.

Warning Signs that May Indicate an Upcoming Allison Transmission Issue

There are several warning signs that may indicate an upcoming Allison transmission issue. These include difficulty shifting gears when accelerating or decelerating; sudden changes in engine speed while driving; sluggish acceleration; slipping gears; loud noises coming from under the hood; fluid leaks near the transmission area; and a burning smell coming from underneath the hood or near the transmission area. If any of these warning signs appear, it’s best to get your vehicle checked by a professional as soon as possible in order to avoid further damage or potential failure of your transmission system.

Professional Services That Can Help With an Allison Transmission Issue

There are several professional services available that can help with an Allison transmission issue. Many auto repair shops specialize in servicing these types of transmissions and can provide diagnosis and repair services at competitive prices. Additionally, there are also independent mechanics who specialize in working on these types of transmissions who may be able to offer more affordable rates than traditional auto repair shops.

DIY Steps for Troubleshooting and Resolving a P0842 Error Code on an Allison Transmission

If you’re looking to troubleshoot and resolve a P0842 error code on an Allison transmission yourself, there are several steps you can take before seeking professional help. First, check all wiring connections between components such as sensors and solenoids as well as any other electrical components related to the transmission system. Also check for loose screws or bolts that could be causing issues with components operating properly. Finally check all fluid levels in both the engine oil reservoir as well as in any other reservoirs related to the transmission system such as coolant level or brake fluid level if applicable . If all these checks come back clear then it may be time to seek professional help from either a local auto shop or from an experienced independent mechanic specializing in this type of work

FAQ & Answers

Q: What is the P0842 code?
A: The P0842 code is an error code that indicates a problem with the Allison Transmission in a vehicle. It typically points to an issue with the internal mechanism or wiring of the transmission, but can also be caused by software glitches.

Q: What are some common causes of a P0842 code?
A: Common causes of a P0842 error code include wiring issues, mechanical issues, and software glitches.

Q: What are some tips for avoiding further problems with the Allison Transmission?
A: Regular maintenance checks and prompt repairs to potential issues can help avoid further problems with the Allison Transmission. Additionally, if you are receiving an error code, it is important to troubleshoot and repair it as soon as possible.

Q: What parts might be needed to repair a P0842 Error Code?
A: Parts that may be needed to repair a P0842 Error Code include wiring harnesses and connectors. Depending on the cause of the error code, additional parts may be necessary for repair.

Q: What are some common symptoms of an Allison Transmission P0842 Error Code?
A: Common symptoms of an Allison Transmission P0842 Error Code include difficulty shifting gears and having an illuminated check engine light. If you notice either of these signs, it is important to have your vehicle inspected as soon as possible.

In conclusion, the P0842 Allison Transmission Code indicates that a problem exists with the transmission fluid pressure switch. This code is usually caused by a faulty transmission pressure switch, low or dirty transmission fluid, or a restricted or clogged transmission filter. It is important to diagnose and repair the issue in a timely manner to prevent further damage to the transmission.

Author Profile

Carl Frisch
Carl Frisch
With more than 30 years in the bicycle industry, I have a strong background in bicycle retailing, sales, marketing and customer service. I have a passion for cycling and a dedication to excellence. As a manager, I worked diligently to increase my capabilities and responsibilities, managing up to eleven mechanics (at Palo Alto Bicycles) and later as a working partner in my own store.

As the shop owner of Spoke n’ Word Cycles in Socorro, NM, the success of the mission was my responsibility, which I pursued passionately since we opened in 2003 through the spring of 2011. I am adept at managing owned and loan inventory, preparing weekly & annual inventory statements, and managing staff. The role as managing partner also allowed me tremendous freedom. I used this personal freedom to become more deeply involved in my own advancement as a mechanic, to spearhead local trail building, and advocating for cycling both locally and regionally.

As a mechanic, I have several years doing neutral support, experience as a team mechanic, and experience supporting local rides, races, club events. I consistently strive to ensure that bicycles function flawlessly by foreseeing issues and working with the riders, soigners, coaches and other mechanics. Even with decades of experience as a shop mechanic and team mechanic, and continue to pursue greater involvement in this sport as a US Pro Mechanic, and UCI Pro Mechanic.

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