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The L5P Duramax engine debuted in 2017 to replace the previous LML model. This engine still uses the 6.6-liter design, but several components were upgraded and updated to increase power and reliability.
Thanks to these reliability improvements, the L5P is one of the most durable diesel engines produced in the modern era.
However, like any other engine, the L5P isn’t perfect. It suffers from a few problems, including MAP sensor failure and fuel injector malfunction. ProSource Diesel takes a closer look at these problems and how the L5P differs from the LML.
L5P Duramax vs LML Duramax
The L5P Duramax enjoys several big changes from the LML engine that greatly improve its performance and reliability.
Some of those changes include a beefier cylinder block, better glow plugs, a new camshaft design, an upgraded EGR system, and an oil cooler with higher capacity than the previous engine.
These changes largely addressed the weaknesses of the LML Duramax for an improved overall engine in the L5P.
New Borg Warner Turbocharger
The new turbocharger is a big upgrade for the L5P Duramax. Previous engines used Garrett turbochargers, which were variable vane turbos that used oil pressure control.
The new turbo is electronically controlled and has a more modern variable geometry design, which makes it more efficient and reliable.
Denso HP4 Injection Pump
In the LML engine, the Bosch injection pump system was a huge problem. When it deteriorated, it sent small metal shavings throughout the fuel system, which caused a destructive chain reaction leading to thousands of dollars in repairs.
In the L5P, this system was replaced with the Denso HP4 pump, which can handle higher pressure without losing power.
Common Problems with the L5P
Although the upgrades from the LML vastly improved the new L5P Duramax engine, a few common problems have cropped up since its debut. As a whole, it’s proven to be a very reliable engine, but if you own one, there are two potential issues to keep an eye on.
MAP Sensor Failure
The manifold absolute pressure (MAP) sensor is located inside the intake manifold. This sensor has the job of sending the ECU readings on the vacuum and positive air pressure, which determines how much fuel the engine should receive to facilitate combustion.
Sensors often get clogged or dirty, which can affect the readings. On the L5P Duramax, the MAP sensor frequently becomes clogged with soot, which causes it to fail or send inaccurate readings to the ECU.
A bad MAP sensor ultimately affects how much fuel is being sent to the engine, which can compromise performance at best and cause major engine damage at worst. Some symptoms of a bad MAP sensor include the following:
– Misfiring
– Check engine light comes on
– Lack of power
– Rough idle
– Stalling or hesitation
– Incorrect air-to-fuel ratio
The MAP sensor on the L5P is primarily a maintenance issue. It requires frequent cleaning to operate properly. Replacing the sensor is only a temporary fix as it will eventually become clogged again without regular cleaning. There are two options to take care of your MAP sensor on the L5P:
– Clean it regularly with a proper cleaner
– Install a MAP spacer
The latter option reduces the heavy soot buildup by creating space between the sensor and the EGR stream, which is primarily responsible for causing the soot buildup.
Fuel Injector Malfunction
Even though the fuel injectors were upgraded for the L5P Duramax, the #4 fuel injector has shown itself to have problems. What happens is that the connector for the #4 injector goes bad and puts the L5P into limp mode.
It throws a PO204 engine code and several engine lights illuminate as engine performance quickly deterioriates. The #4 injector might fail, but most of the problems reported are with the connector and not the injector.
Symptoms of a malfunctioning fuel injector on the L5P Duramax include the following:
– Limp mode engages
– Various engine lights come on
– Misfiring
– Rough idle
– Shaky engine
– Poor performance
– Engine codes P0204, P020D, P0300
If it turns out to be the #4 injector connector, the primary fix for this issue is to get a gold-plated connector that makes a better connection. Some owners also replace the connector with an LBZ connector.
Reliability of the L5P Duramax
Although the emissions-era Duramax engines have had spotty reliability reports, the L5P engine has fixed that. The various improvements and removal of the previous injection pump have strongly increased the L5P’s reliability.
With proper maintenance, the L5P is easily a 350,000-mile engine with some owners reporting well over that.
Rely on ProSource Diesel for all your diesel parts needs, including replacement parts and upgrades for the L5P Duramax engine. We are where the diesel repair shops shop for parts.
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The post L5P Duramax Problems appeared first on Prosource Diesel.
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