Diagnostic Trouble Codes: P0471 (Exhaust Pressure)
Error code P0471 indicates a problem with the exhaust pressure sensor range/performance. This essentially means that the powertrain control module (PCM) has detected that there is an abnormal voltage reading from the exhaust back pressure sensor circuit. There are a variety of reasons that a vehicle would throw this code, such as a sensor circuit malfunction, injector circuit malfunction, exhaust gas recirculation issues, a damaged fuel temperature sensor or control circuit bank malfunction to name but a few. Typically, you will find this code in turbocharged or diesel engines.
Your vehicle may still be drivable with this code stored; however, you do not want to ignore it for too long. Ignoring the problem could lead to more serious issues down the road (quite literally). Once the check engine light comes on and your scanner reads this code, try to ensure the issue is resolved as soon as possible.
What causes the P0471 DTC?
As with many issues that may come up in your vehicle, check to see if the manufacturer has issued a bulletin with a PCM update. This could save you a lot of time and troubleshooting. Plus, a PCM update will typically be part of a recall process and not require any payment on your part. Of course, free repairs are the best repairs. However, if there is no bulletin relating to a PCM update, then these are the most likely causes of a P0471 code:
- Fault exhaust gas pressure sensor
- Blockage in the tube between the exhaust manifold and the pressure sensor
- Gas recirculation system issue
- PCM issue
First, the PCM issues are incredibly rare and, if there was a PCM issue, it would likely simply be a software update which would have been noticed above when you checked the bulletin.
A good starting point for resolving a P0471 code is to disconnect the tube that connects the pressure sensor to the exhaust manifold. Inspect the tube for any blockages. You may need to blow through the tube to see if air can pass easily through. If not, use a thin wire to push through any debris that may be blocking airflow through the tube.
While you’re working near the pressure sensor, find the connectors and wiring. Ensure the connectors are clean and there are no exposed wires. These could cause the sensor to throw a P0471 code. Any corrosion or burning on the connectors could also indicate what is causing the problem. If the connectors look like they should be cleaned, then buy some electrical contact cleaner, clean the connectors and terminals, and then let them air dry.
If the code is still not resolved, the next step would be to inspect the tube that connects the turbocharger to the intake manifold. Any leaks would cause this code to appear. If necessary, the tube will need to be repaired or replaced in order to resolve the P0471 code. A minor leak may be fixed by simply tightening the hose band clamps.
One of the last things to check would be the exhaust pressure sensor itself. Sometimes these sensors can become clogged with soot. Check to ensure that the pressure sensor is clean. If cleaning does not resolve the issue, it could indicate that the sensor has failed or there are other issues with the wiring.
Each wire leading to the sensor should test at 5V. Anything other than that could indicate that the wiring needs to be replaced or that there is an issue with the PCM. Be sure to check all 3 wires.
If the voltage is correct to the exhaust pressure sensor then this likely indicates that the sensor itself has failed. Replacing the sensor is the final step in troubleshooting. If a brand new sensor has been put in and all other avenues have been exhausted then this likely indicates a problem with the PCM. However, as mentioned, that is one of the most unlikely causes of a P0471 code.
Hopefully, a PCM update is all you need to clear out this code. If not, be sure to follow the above instructions carefully and consult a professional if required.