Understanding the P0088 Code in Your 2022 Ram 3500 Cummins 6.7 Diesel: Causes and Solutions

Customer Vehicle:

2022 Ram 3500

6.7 Cummins

158,000 Miles

Customer Complaint:

Check Engine Light On

Poor Drivability

Basic Maintenance Service

Presale Inspection

CEL Status: On

Codes:

P0088 high rail pressure

Status: Repaired

This post is about a code we see pretty often around our shop- P0088 (high rail pressure) in newer Ram trucks like the 2022 Ram 3500 (also included are the 2500 models) with the 6.7 Cummins Turbo Diesel that recently came through for service. We are going to walk you through our process for diagnosis and repair. Hopefully this will help some of you that are having a similar issue.

Vehicle Evaluation-

This vehicle had relatively low mileage at only 158k miles, but still presented with many of the same issues. We do have to be careful because mileage alone isn't always the most accurate determination of maintenance needed or overall condition. We've seen vehicles with similar mileage and had over 10,000 engine hours! This particular customer's vehicles all receive a basic maintenance package that consists of complete fluid services, lights, wipers, and a road test. Basically anything someone looking to purchase a vehicle would require before purchase. We can't make them brand new, but when they leave our shop they are properly sorted! Nothing is overlooked!

The customer's major concern here was the Check Engine Light(CEL) and driveability. In this instance, we had a P0088 code "high rail pressure" that came back almost immediately after clearing. At idle the computer was reading at or above 9000 psi when the computer was only commanding around 5000 psi at idle. When driving the rail pressure would fall in line within normal specs. We also noticed while doing our diagnosis that when holding the engine at 2000+ rpm, with no load, the rail pressure would stabilize in the normal range. The issue was only present at idle. 

Basic Maintenance-

We noticed while changing the fuel and water separator filters we found what we believe was mud, or at the very least some type of debris, in both housings. The tech notated that both filters were black almost as if they were coated in a tar like substance. We knew at this point there was a definite fuel system problem or contamination. We did check for blockages or kinks in the return system just to be safe, but for now we had a direction! We are most likely dealing with contamination. 

Diagnosis-

During the course of our diagnostic procedure we checked the fuel rail pressure sensor, fuel control actuator, and all lines for leaks, kinks, or other obvious signs for an issue. Not seeing any other issues, we suspected the fuel pressure regulator was probably the cause because everything else in the system was working properly and well within spec. We pulled the fuel pressure regulator(FPR) and this is what we found:

It’s hard to see with the naked eye, but the end of the FPR is actually a tiny screen that allows unused fuel to return back to the tank. Many thanks to @TechnicianRed for allowing us to use a photo from his YouTube page. As you can see, the tip of the FPR is under a microscope! So now we know the problem, the debris we were seeing at the beginning has clogged the screen of the FPR.

Off topic for a moment! Common rail diesels running a CP4 are very temperamental when it comes to using aftermarket sensors. It is always our recommendation to go with OEM sensors when replacing one. Most of the time those are Bosch, but we did not do that this time only because our customer had this vehicle sold already and needed it back ASAP. Our customer was given the option to wait for an OEM part or to move forward with a quality aftermarket replacement so we moved on with the repair using an aftermarket component.  Back on topic! We called the dealer to check availability and to order the FPR. Of course it was on national back order. There were only two in our area, but that dealer wasn't able to sell them because they were for other customers. Our other aftermarket suppliers were not showing a listing for this particular sensor so we began looking for alternatives like maybe a known good used part when another shop mentioned that the 5.0 Cummins in the Titan XD were the same spec, but a slightly different part number. We were able to research this and verify that it was true! Same issue though, none were available! Then we found that an aftermarket "OE replacement" part. We ordered it and to no surprise it is literally a repackaged Bosch OE sensor in an aftermarket box. 

The Repair-

We installed the FPR, test drove the truck, and sent it on its way. It's been several weeks and so far we have not yet heard back about the truck having the same issue. If you have a Ram 3500 6.7 Cummins Diesel with a P0088 code keep this post in mind. If you ever have any questions or concerns, please feel free to send us a message. If we can help we will!