P2459 Code in RAM 3500 – What's Wrong and How to Fix?

In short, the P2459 code in your diesel RAM 3500 means that the regeneration happens too often. It may be due to clogged DPF, issues with software, or problems with engine work. Unfortunately, locating the actual problem may be challenging, even dealerships struggle to name the actual culprit of this code after a fast inspection.

P2459 code highlights

• Level of urgency:Medium
• Possible culprits:DPF full, regeneration needed
• Price for repair:$0 - $800
• If neglected:DPF may require replacement soon
• DIY repairs:Impossible
• Can you drive?Yes

Symptoms and circumstances for the P2459 code

This fault code may show up in a diesel-powered RAM truck. The 6.7 Cummins diesel engine is used in heavy-duty trucks and is pretty popular among American buyers. Yes, it's not problem-free, but just like any other similar engine on the market. For example, the 6.7 Power Stroke in Ford HD trucks can also show the P2459 code pretty often.

So, this error code means that the regeneration process takes place very often. It's OK for the truck to start regeneration once every 250-450 miles depending on the driving conditions (highway, city, speed, RPMs, etc.). But if regeneration takes place once every 75-100 miles, the P2459 error code will trigger the check engine light on the dash of your vehicle.

Also, you may notice different symptoms:

• the check engine light will be on and it won't reset after you turn the car off and on;
• regeneration will actually start very often and you will feel that it's not OK;
• during the regeneration process, the vehicle may lose power and work harshly;
• regeneration may start in different circumstances, not only when you drive at a steady speed;
• your engine may rev up at idle when the regeneration is in progress;
• the code will sit there for a long time and won't reset until you solve the problem.

Well, on some very rare occasions, the P2459 code may not mean an actual problem. It may also tell you that the regen is taking place too often because you've been driving in extremely slow city traffic with a lot of stops and a large amount of idling. In this case, the DPF will be full much earlier than usual and the car will start forced regen much earlier than expected.

If this is the case, you may just take your RAM truck to a highway and drive 30-50 miles at high speed to let the DPF clean itself. But if it doesn't work and the P2459 code isn't cleared after a day or two, you should inspect the car and find what triggers the code.

What are the common reasons for the P2459 code in the RAM 3500?

So, the 6.7 diesel engine in the RAM heavy-duty trucks has a large DPF that gathers soot and particles forming in the process of diesel combustion. When the filter is full, the car heats it up and burns the particles turning them to ash. For this, it raises the RPM and changes the air-fuel mixture ratio for some time. This is a very short and primitive explanation of how regen works in diesel engines.

So, if the regen process happens too often, there is a problem with this system. And now we'll see what exactly can influence it.

1. DPF is clogged and needs cleaning

If your RAM truck has more than 100,000 miles, it's very possible that the DPF is clogged and can't be cleaned just by regeneration. It still can be cleaned with the manual methods. Unfortunately, this doesn't come for free and the manual cleaning of DPF units will cost you quite a lot of money. Another problem is that shops don't even guarantee that this will help.

Manual cleaning of DPFs will help in case there are no damages in the filter. If the filter was extremely overheated or damaged physically, it may have killed the unit and now it has to be replaced.

2. DPF is totally dead

If manual cleaning doesn't help, chances are you will need a new DPF. It's not really common for 6.7 Cummins engines to require new DPFs though. They are very tough and can go as long as the engines but still, DPF death is possible.

Some bad news can spoil your mood - the new DPF and the labor will cost you about $2,000 which is appropriate in that case only when you have a relatively new and fresh truck with no problems and technical issues.

3. MAF problem

Mass airflow sensor can malfunction and cause problems with the air-fuel mixture. It means that the ECU will just be unable to prepare the proper mixture for regeneration. It will send the signals but the engine will not do what the ECU wants from it. So, the regeneration process will not be completed properly.

After your truck goes 50-70 miles, the sensors in the DPF again tell the ECU that the regeneration is needed urgently. After several cycles of such regen, the ECU will throw the P2459 code. This problem is really common for Cummins engines and is worth having a look at once you see this code.

4. Air filter or vacuum leak

Problems with air intake can also cause this problem. The reason is the same as in the third section above - the engine just can't prepare the proper air-fuel mixture. Although I haven't heard about problems with the intake manifolds in the 6.7 Cummins, I've heard a lot about the issues with aftermarket filters that literally prevented engines from breathing properly.

You may take the filter out, then clear the code and see if it comes back. This is the free way to check the possible problem.

5. Software problems

I haven't found any service bulletins or recalls about this problem from Chrysler but I'm pretty sure there are some 2018-2020 RAM 3500 trucks that require attention in terms of software updates.

It may be that an existing software in your truck develops a glitch and you just need to update it. The only place I can recommend you to go to, in this case, is the dealership. They will update your RAM to the latest version of its software and check whether it helps you deal with the DPF regen code.

Can you drive with the P2459 code in your RAM 3500?

Sure, you can drive and there is nothing you can make worse, in this case. But ignoring this problem is not the best strategy for a RAM 3500 owner. If you use the OBD2 scanner and see that the ECU throws the P2459 code, you should keep driving the vehicle to help it regen the DPF properly. But you should also understand that the code means something is wrong with the entire system.

The best thing you can do is to plan a visit to the dealership or to a good repair shop that knows your RAM truck model really well. They know the common reasons for this unpleasant code and they will certainly help you find the actual reason for this behavior of your vehicle.

I don't recommend driving a thousand miles with the check engine light and the P2459 code in the ECU. In this case, you may get problems with the oil (dilution and high level), issues with the DPF (it may just get clogged and require replacement), or with other units and components that take part in the regeneration process.

What can you do to solve the issue?

There is not much you can do if you see this code. The problem needs professional inspection and repair.

But I still have several recommendations:

• check if you changed the oil on time and let the ECU know about it - modern Cummins engines may throw some kinds of codes if the oil change is not registered in the ECU;
• check the oil levels - if the level is too high or too low, you should learn why, otherwise, the engine may show other kinds of problems soon;
• confirm you are using high-quality diesel fuel - low-grade fuel will not allow your engine to go through regeneration as needed;
• take out the air filter and make sure that there are no obstructions in the air hoses under the hood of your truck.

If this doesn't help and doesn't let you locate the issue, you may want to call your dealer and make an appointment. Professional inspection will help you find and quickly solve the problem. Of course, let the mechanic or manager at the dealership know every single detail and symptom you experience with the truck - this will make the diagnostics much easier and cheaper.