Technical Description of OBD-II Trouble Code
The code indicates a range/performance issue with the exhaust pressure sensor.
What does that mean?
This code is applicable to various engines that use variable nozzle turbochargers, such as Ford trucks with 6.0L diesel engines starting from 2005, Ford EcoBoost engines, Cummins 6.7L engines from 2007, Mercedes 3.0L engines from 2007, and Cummins 3.0L 6 cyl engines in Nissan pickups from 2015. However, it may also occur in other vehicle makes.
The code specifically relates to the discrepancy between the incoming signal from the exhaust pressure sensor and the intake manifold pressure or ambient air pressure during key on. This discrepancy can be due to an electrical circuit fault or a mechanical issue.
Code P0470 may also be present simultaneously with the P0470 code. The only difference between these two codes is the duration of the problem and the specific electrical/mechanical issue affecting the sensor, circuit, or engine controller. Troubleshooting steps may vary depending on the manufacturer, whether the engine is gas or diesel, the type of exhaust pressure sensor, and the wire colors.
A typical exhaust pressure sensor:
Related trouble codes for the exhaust pressure sensor include:
Symptoms
The symptoms of a P0471 engine code may include:
Potential Causes
The common causes for this code to be triggered are:
Diagnostic and Repair Procedures
A good starting point is to search for any technical service bulletins (TSBs) related to your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram available to address this issue, so it is worth checking before pursuing other troubleshooting steps.
Next, locate the Exhaust Pressure Sensor in your vehicle. Once found, disconnect the tube that connects the sensor to the exhaust manifold. Try blowing through the tube. If you are unable to blow through it, use a small piece of wire to dislodge any trapped carbon that may be causing the fault code. If you notice a significant amount of water being blown out, it may have been the cause of the code.
If the tube is clear and unobstructed, visually inspect the connectors and wiring. Look for any signs of chafing, rubbing, bare wires, burn spots, or melted plastic. Separate the connectors and carefully examine the terminals inside. Check for corrosion, burns, or any abnormal green coloration. If necessary, use electrical contact cleaner or rubbing alcohol to clean the terminals. After cleaning, let them air dry and apply dielectric silicone compound to ensure proper contact. Additionally, check for any leaks in the tube connecting the turbocharger to the intake manifold. Inspect all tube connections around the turbocharger and intake manifold, and tighten any hose or band clamps as needed.
If you have a scan tool, clear the diagnostic trouble codes from memory and monitor if the code returns. If it does not, the issue was likely related to the connections.
If the code persists, further testing of the sensor and its circuits is necessary. Typically, the Exhaust Pressure sensor has three wires.
Disconnect the harness connected to the Exhaust Pressure Sensor. Use a Digital Volt Ohm Meter (DVOM) to test the 5V power supply circuit to ensure it is receiving the correct voltage (Red lead to the 5V power supply circuit, black lead to a good ground). If the sensor is receiving 12 volts instead of 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts or consider the possibility of a faulty PCM.
If the power supply circuit is functioning correctly, use the DVOM to check the sensor signal circuit for 5V (Red lead to the sensor signal circuit, black lead to a good ground). If there is no 5 volts or if you measure 12 volts, repair the wiring from the PCM to the sensor or consider the possibility of a faulty PCM.
Next, check the ground circuit of the Exhaust Pressure sensor. Connect a test light to the positive terminal of a 12V battery and touch the other end of the test light to the ground circuit of the Exhaust Pressure Sensor. If the test light does not illuminate, there is a problem with the circuit. If the test light illuminates, wiggle the wiring harness connected to each sensor to check for any intermittent connections indicated by flickering of the test light.
If all the tests have been passed and the P0471 code continues to appear, it is likely that the Exhaust Pressure sensor has failed. However, the possibility of a faulty PCM cannot be ruled out until the sensor is replaced.
