Technical Description of OBD-II Trouble Code
The circuit for the Exhaust Pressure Sensor is experiencing intermittent or erratic behavior.
What does that mean?
This generic diagnostic trouble code applies to all engines that use variable nozzle turbochargers (gas or diesel). It was first observed in 2005 on Ford trucks equipped with 6.0L diesel engines, and later on Ford EcoBoost engines. It eventually appeared in the Cummins 6.7L in 2007, the 3.0L in the Mercedes lineup in 2007, and the Cummins 3.0L 6 cyl in the Nissan pickups starting in 2015. However, it is possible to encounter this code in other makes as well.
This code specifically relates to the exhaust pressure sensor not providing a consistent signal that matches the intake manifold pressure or ambient air pressure during engine operation. The issue can be either an electrical circuit fault or a mechanical problem.
Codes P0471, P0472, or P0473 may also be present alongside P0474. The difference between these codes lies in the duration of the problem and the specific electrical or mechanical issue affecting the sensor, circuit, or engine controller.
The troubleshooting steps may vary depending on the manufacturer, whether the engine is gas or diesel, and the type of exhaust pressure sensor and wire colors used.
A typical exhaust pressure sensor:
Related exhaust pressure sensor trouble codes:
Symptoms
The symptoms of a P0474 engine code may include:
Potential Causes
The typical causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is always 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’s worth checking before pursuing other troubleshooting steps.
Next, locate the Exhaust Pressure Sensor on your particular vehicle. Once found, disconnect the tube that connects the sensor to the exhaust manifold. Try blowing through the tube. If you can’t, attempt to dislodge any trapped carbon by running a small piece of wire through it. This carbon buildup is likely causing the fault code.
If the tube is clear and free, 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 and a light plastic bristle brush to clean the terminals. Afterward, let them air dry and apply some dielectric silicone compound where the terminals make contact.
Next, ensure that the tube connecting the turbocharger to the intake manifold is not leaking. 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 see if this code returns. If it doesn’t, then the issue was likely with the connections.
If the code does return, further testing of the sensor and its associated circuits is necessary. Typically, there are 3 wires connected to the Exhaust Pressure Sensor. Disconnect the harness going to the sensor and use a Digital Volt Ohm Meter (DVOM) to test the 5V power supply circuit. Ensure that it is receiving the correct voltage (Red lead to the 5V power supply circuit, black lead to a good ground). If there is 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. Verify that it is receiving 5 volts (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 at 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 doesn’t illuminate, there is a problem with the circuit. If it does illuminate, wiggle the wiring harness going to each terminal to check for intermittent connections.
If all the tests have been passed and the P0474 code continues to appear, try wiggling the sensor wiring harness while monitoring the scan tool. If the code returns, it likely indicates an intermittent connection in the harness. If the code doesn’t return, it is possible that the Exhaust Pressure sensor has failed, although a faulty PCM cannot be ruled out until the sensor is replaced.
