Technical Description of OBD-II Trouble Code
The code indicates a range/performance issue with the “B” exhaust pressure sensor.
What does that mean?
This generic powertrain/engine diagnostic trouble code is applicable to various engines that use variable nozzle turbochargers. It was first observed in 2005 on Ford trucks equipped with 6.0L diesel engines, Ford EcoBoost engines, and later on 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 vehicle makes as well.
This 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. The issue can be either an electrical circuit fault or a mechanical problem.
It is possible for code P047A to be present simultaneously with code P047B. The only difference between these two codes is the duration of the problem and the specific type of 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. Consult a vehicle-specific repair guide to identify the “B” sensor for your particular vehicle.
A typical exhaust pressure sensor:
Related trouble codes for exhaust pressure sensor “B”:
Symptoms
Indications of a P047B 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 to search for any relevant technical service bulletins (TSBs) for 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 paths.
Next, locate the Exhaust Pressure Sensor on your vehicle. Once found, disconnect the tube that connects the sensor to the exhaust manifold. Attempt to blow through the tube. If you are unable to do so, try running a small piece of wire through it 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 (metal parts) inside. Check for signs of corrosion, burning, or a greenish color, which may indicate abnormality. If necessary, use Electrical Contact cleaner or rubbing alcohol and a light plastic bristle brush to clean the terminals. After cleaning, let them air dry and apply some dielectric silicone compound (the same type used for light bulb sockets and spark plug wires) where the terminals make contact. Additionally, 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 loose hose or band clamps.
If you have a scan tool, clear the diagnostic trouble codes from memory and monitor if this code reappears. If it does not, then the issue was likely related to the connections.
If the code does return, further testing of the sensor and its associated circuits is necessary. Typically, there are three wires connected to the Exhaust Pressure sensor.
Disconnect the harness connected to the Exhaust Pressure Sensor. Using a Digital Volt Ohm Meter (DVOM), test the 5V power supply circuit to ensure that 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 between the PCM and the sensor to resolve any short to 12 volts or potential PCM issues.
If the power supply circuit is functioning correctly, use a DVOM to check if there is 5V on the Exhaust Pressure Sensor signal circuit (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 on the signal circuit, repair the wiring between the PCM and the sensor, or consider the possibility of a faulty PCM.
Next, verify that there is a proper ground connection 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 does not illuminate, it indicates a problem with the circuit. If the test light does illuminate, wiggle the wiring harness connected to each sensor to check for any flickering of the test light, which would indicate an intermittent connection.
If all the tests conducted so far have passed and the P047B code continues to appear, it is likely that the Exhaust Pressure sensor has failed. However, it is important to note that a faulty PCM cannot be ruled out until the sensor has been replaced.
