Technical Description of OBD-II Trouble Code
Malfunction in Exhaust Pressure Sensor “B”
What does that signify?
This generic powertrain/engine diagnostic trouble code is applicable to all engines that utilize variable nozzle turbochargers (gas or diesel). It was first introduced in 2005 on Ford trucks equipped with 6.0L diesel engines, all Ford EcoBoost engines, and later extended to include the Cummins 6.7L in 2007, the 3.0L in the Mercedes lineup in 2007, and most recently the Cummins 3.0L 6 cyl in the Nissan pickups starting in 2015. However, it is possible to encounter this code in other makes such as VW.
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 at key on. The cause can be either an electrical circuit fault or a mechanical issue.
Code P047B may also be present simultaneously with the P047A code. The only difference between these two codes is the duration of the problem and the type of electrical/mechanical issue that the sensor/circuit/engine controller is experiencing. Troubleshooting steps may vary depending on the manufacturer, whether it is a gas or diesel engine, the type of exhaust pressure sensor, and the wire colors. Consult a vehicle-specific repair guide to determine which sensor corresponds to the “B” sensor in your particular vehicle.
A typical exhaust pressure sensor:
Related trouble codes for exhaust pressure sensor “B”:
Symptoms
The symptoms of a P047A engine code may include:
Potential Causes
The typical 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 embarking on a potentially lengthy and incorrect troubleshooting path.
Next, locate the exhaust pressure sensor in your specific vehicle. Once found, disconnect the tube that connects the sensor to the exhaust manifold. Attempt to blow through the tube. If 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 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 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/band clamps.
If you have a scan tool, clear the diagnostic trouble codes from memory and observe if this code reappears. If it does not, then the issue was most likely related to the connections.
If the code does reappear, 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 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 power (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 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 instead, repair the wiring from the PCM to the sensor or once again consider the possibility of a faulty PCM.
If the signal circuit is also functioning correctly, check if 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 connected to the Exhaust Pressure Sensor circuit ground. 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 see if the test light flickers, indicating an intermittent connection.
If all the tests conducted so far have passed and you continue to receive a P047A code, it is likely that the Exhaust Pressure sensor has failed. However, the possibility of a failed PCM cannot be ruled out until the sensor has been replaced.
