This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
P2002 - Diesel Particulate Filter Efficiency Below Threshold Bank 1
If you don’t drive a diesel engine vehicle, you will probably never see this code come up on your OBD-II scanner. For those who do, P2002 is the trouble code generated by the ECM when it detects a problem with an SAE-controlled particulate exhaust filter. Changes in exhaust back pressure outside of manufacturer specs triggers a Bank 1 trouble code if the problem is occurring on one set of cylinders, and Bank 2 for the opposing set.
Exhaust problems can have any number of causes, but with a P2002 trouble code you can usually narrow it down to one of the following:
- The particulate exhaust filter is broken or clogged
- The back pressure sensor is damaged or broken on Bank 1
- There is a leak somewhere in the exhaust system as it flows out of Bank 1
- Poor quality diesel fuel
The underlying issue with your exhaust particulate filter is purely an emissions management problem. Most owners will only note the Check Engine Light or DPF light on their dashboard and pull trouble codes. It is possible in extreme cases that your engine will idle rough or that you will observe black, sooty smoke blow out the tailpipe, but that’s fairly rare. In the vast majority of cases, you wouldn’t even know you had an issue unless your indicator comes on.
Troubleshooting this code is a fairly simple process. If you are confident in your automotive DIY skills, you can probably handle most of it on your own. Here’s a step-by-step guide to getting to the root cause of your P2002 trouble code:
Step one should involve a close visual inspection of all the associated wiring harness for the back pressure sensor and around the particulate exhaust filter. Overlooked worn or broken connectors and wiring are the number one cause of unnecessary automotive parts replacement.
If your wiring appears intact, it’s time to pull the particulate filter and the exhaust back pressure sensor. Check closely to see if either component is damaged or clogged. Sometimes a quick cleaning with some brake/carburetor cleaner is all you need to fix the back pressure issue, so cleaning and retesting with your OBDII code is a good idea at this phase.
Hook up your scanner and take a test drive the vehicle while tracking the back pressure sensor readings. If Bank 1 sends different readings than Bank 2, you’ll need to do some more troubleshooting to decide if it's the filter or the sensor that needs replacement. If you’ve already cleaned out both carefully though, chances are the sensor and not the filter is the issue.
Poor quality diesel fuel is a probable cause that gets overlooked all too often. Take your vehicle for a drive at highway speed to try and blow any carbon or other particulates out of the exhaust filter and verify if the code keeps coming up. Sometimes that highway test drive resolves the problem for you.
How serious is this?
Leave this trouble code in the ECM for too long, and your vehicle computer may trigger what is known as “limp mode.” The ECM will limit both top speed and engine power to protect the internal components of the drivetrain. The only way to get it out of limp mode is to correct the underlying cause of the trouble code and reset the ECM.
What repairs can fix the code?
Most of these are quick and easy fixes. Here are the most common:
- Clearing the diesel particulate filter (easy and virtually free)
- Changing the diesel fuel (can be expensive depending on how much bad fuel you are replacing)
- Replacing the diesel particulate filter (not too expensive and fairly easy to do yourself)
- Replacing the back pressure sensor (more expensive than replacing the filter and requires more complex repair skills)
You may see some of these other related codes pop up when you get a P2002 trouble code. They may or may not be relevant to the root cause.
This isn’t an operation critical problem for your diesel burning vehicle, but it is not something you want to ignore for an extended time period. If you can pull and reset codes on your own, try checking the wiring, filter and sensor for yourself first.
If you’re not comfortable with these tasks, book it for a trip into the shop and have a professional evaluate it. Above all, make sure you take it for that highway speed test drive first to make sure you don’t just need to blow the carbon out of the exhaust system. That alone can save you a significant amount of time and effort.