L5P Duramax Problems (Common Issues Explained!)

In this article, we are going to be looking at the L5P Duramax problems that you need to be on the lookout for and how you can solve some of them.

The L5P Duramax is a version of the V8 diesel Duramax that was introduced in 2017 and with 445HP and 910-pound feet of torque, it is the most powerful pickup truck engine from GM. It is described by many as a muscle truck because of the sheer power that this engine produces.

Though it is a great piece of engineering and known for being very reliable, it does have some problems that have been reported by owners over the years and in this post, we are going to be looking into them. What are the most common problems with the L5P Duramax?

In short, The most commonly reported problems that the L5P Duramax has are the Allison 1000 transmission, MAP sensor failure as well as fuel injector failure. Since it’s relatively new on the market, there is still very limited information available on it as far as problems are concerned.

Let’s now look into these different issues one by one.

l5p Duramax problems (2017,2018,2019,2020 and 2021 years)

Allison 1000 Power Transmission Issues in the Duramax L5P

Though this can’t be listed as an actual problem on this engine, the transmission `will struggle somewhat if you want to make modifications `for `additional horsepower.

The stock transmission is incapable of handling `up to 500whp and if you want to `add to that and push to say, maybe 600whp, you will have to make some expensive modifications to the transmission. A way around making the transmission upgrades is to make other upgrades that work out cheaper in the long term.

These include hydraulic upgrades, multi-disc torque converter, and transmission cooler as well as improved friction materials. These will help the transmission hold up better under the added strain.

217MAP Sensor Failure on the Duramax L5P

Another issue that has been noted on the engine is an issue with the MAP sensor. Known as the manifold absolute pressure sensor, the job of the MAP is to read vacuum and positive air pressure levels then send these to the ECU.

These readings are used to determine how much air is supposed to be sent to the engine for optimal combustion which results in efficient engine performance.

The MAP sensor can get clogged up with soot and other combustion residue leading to it failing or giving inaccurate readings. When this happens, the engine will no longer perform at optimum levels and when left unattended, this issue can lead to catastrophic engine failure.

When you notice your engine stalling, poor performance, engine misfire, rough idling, and other associated issues, the MAP sensor may be the issue and needs to be checked. It needs to be cleaned regularly to avoid having this issue. There really isn’t a need to let it get to the point where it completely gives up.

Replacing a faulty MAP sensor will cause the clock to reset which is an unnecessary problem. Just make sure to clean it regularly and you will not have this problem.

Fuel Injector 4 Failure on the L5P Duramax

The connector for fuel injector number 4 has been known to fail on rare occasions needing to be replaced. The issue is not with the injector itself though that possibility is not a farfetched possibility even though it’s very rare.

When the injector fails, your vehicle will get into limp mode and give a P0204, P0300, or P0204 engine code and go into limp mode. To deal with this issue, replace the stock connector with a gold-plated one or an LBZ connector.

Other symptoms to watch out for are Stabilitrak or ABS lights, misfiring, rough idling, shaky engine, and overall poor performance. Any problem that puts your truck into limp mode is worth looking into immediately.

Is the L5P Reliable?

The L5P is a very reliable engine with a lot of capability even at the stock level. The problems highlighted in this post are really splitting hairs when you look at it. It is considered the best post emissions Duramax from GM. The engine itself is a tuner’s dream. At stock, the fuelling system is capable of handling up to 800whp, the turbo can handle 600whp and the engine redesign from the preceding version make it an easy engine for tuners to work with.

Conclusion on l5p duramax problems

The L5P is one of GMs best engines and is a reliable engine. It’s really difficult to find things that are wrong with it and in this post, I touched on issues that are actually very rare in occurrence.

The truth is, there really isn’t much to complain about when it comes to this particular engine. This is one of the engines which; if you take care of it, it will take care of you. It’s not uncommon for an L5P Duramax to get to 500,000 miles and beyond.