Duramax P0087 Fuel Pressure Code

So we see this in the shop weekly and also online all the time. Driving down the road or starting the truck up and pops with a P0087 code. We'll walk you through a quick tutorial on what it means, its likely causes, and fixes for that issue.

The P0087 code is a fuel pressure code signaling the pressure is below spec. The sensor is located on the fuel rail, and this is what triggers the code to be thrown.

Sometimes the vehicle may experience symptoms and sometimes it won't. You can also view the fuel pressures if you have a monitor device, scan tool, etc. Most likely you'll see the two pressures being far off from each other or one coming down faster etc. If you experience symptoms, it may be laggy, misfires, or could even lunge so to speak.

Now there are several outcomes to what might be causing the actual problem to occur so we'll go through them but just remember sometimes it can be more than one also.

Possible Causes:

#1 - Air introduced into the system (a lot of the time the factory filter head or the filter itself will be leaking or might be clogged up)- this can cause the low-pressure code to pop up.

Fix - Change the filter and or check the filter head for any leaks or cracks (very common).

Permanent Fix: Buy a lift pump, remove the factory filter/head with a bypass hose and go on about your way. The lift pump is a flow-through design so it will still filter the fuel even if it stops working.

#2 - Collapsed fuel line/ leaking fuel line somewhere in the system. This one is less likely, but you literally have to check the lines on the rails, the cp3 pump, and all the way back to the fuel tank. (check the sending unit/ tank as well).

Fix - Repair/ Replace fuel line.

#3 - Faulty Fuel Pressure Sensor: Again not as likely but it is something that is faulty and therefore gives a false reading to the vehicle's computer.

Fix - Replace with a GM FPS. Even the shimming kit for the sensor isn't a bad idea and might be something to do especially on modded applications. WE DO NOT RECOMMEND INSTALLING A FUEL RAIL PLUG! (This does not solve the problem and it can actually cause the rail to crack if too much pressure occurs inside the rail and can't blow off).

#4 - Weak CP3 / CP4 pump: This can occur and is more likely, especially in older/ higher mileage trucks. Some signs of this along with the code might be hard starts, excessive smoke (be careful as this can also be a boost leak), laggy, fuel knocks, and not reaching certain PSI at WOT. These can all be signs of a potentially weak or bad cp3/cp4 pump. You can also use the pressure test port as well to check what the fuel psi is.

#5 - Weak/ worn injectors: Injectors over time become worn down due to all the heat cycles and likely timing messes with the crazy tuning people run (over returns the fuel). Again this is more on the less likely side of things, but it can happen and cause that issue/code. Balance rates will not tell you the whole story so again would have to be tested by a shop. Always start with the easiest/ least expensive things to replace first then move on down the line if it doesn't solve your problem.

Solution:

As we mentioned above any of these could be the issue, or it could be several combined, but typically these are what cause the P0087 code.

We can say about 90% of the time its an issue with the filter, head, or a collapsed line, which can typically be fixed permanently by the lift pump (lots of benefits to running a lift pump even with a good fuel system), removal of the filter and head and fixing the bad fuel lines. Now some people do use this as a bandaid where the issue is still out there, so while it can fix the issue, you may want to make sure it's not any of the other issues as well.

Other areas you might see a big fuel difference in actual vs. desired rail pressure is in the tuning with fuel/timing added etc. This is a different circumstance and goes back to even the shimming kit to use, but this would be something your tuner needs to dial back to accommodate your mod setup.

We hope this helps some with explaining the issue and ways to fix it potentially. Thank you!

Need further assistance on service or parts please reach out to us!

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