What does it mean?
This generic powertrain/engine diagnostic code applies to all engines using variable nozzle turbochargers (gasoline or diesel), starting around 2005 on Ford trucks with 6.0L diesel engines, all Ford EcoBoost engines, and eventually leading to the Cummins 6.7L in 2007, the 3.0L in the Mercedes lineup in 2007, and more recently the Cummins 3.0L 6-cylinder in Nissan vans starting in 2015. This does not necessarily mean you won’t get this code in a VW or other brand.
This code is strictly concerned with the incoming signal from the exhaust pressure sensor not matching the intake manifold pressure or ambient air pressure during power-up. This could be an electrical circuit fault or it could be mechanical.
The P047A code may also be present at the same time as P047B. The only difference between these two codes is the duration of the issue and the type of electrical/mechanical problem encountered by the sensor/circuit/engine controller. Troubleshooting steps may vary by manufacturer, gas or diesel, type of exhaust pressure sensor, and wire colors. Refer to a vehicle-specific repair guide to determine which sensor is the “B” sensor for your particular vehicle.
A typical exhaust pressure sensor:
Exhaust Pressure Sensor
Associated “B” Exhaust Pressure Sensor Fault Codes:
P047A Exhaust Pressure Sensor “B” Circuit
P047C Exhaust Pressure Sensor “B” Circuit Low Value
P047D Exhaust Pressure Sensor “B” Circuit High
P047E Exhaust Pressure Sensor “B” Circuit Intermittent
Symptoms
Symptoms of a P047B engine code may include:
Check Engine Light on
Lack of power
Unable to perform a manual regeneration – burn soot from the particulate filter. It looks like a catalytic converter but has temperature sensors and pressure sensor probes inserted in it.
If it is unable to perform regeneration, it may eventually result in a no-start condition.
Potential Causes
Typically, the causes for this code to set are:
Blockage in the exhaust manifold tube to the pressure sensor
Exhaust gas recirculation system / air intake / boost air leaks
Exhaust pressure sensor
A Powertrain Control Module (PCM) may be faulty (very unlikely)
Diagnostic and Repair Procedures
A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path.
Next, locate the exhaust pressure sensor on your specific vehicle. Once located, disconnect the tube connecting the sensor to the exhaust manifold. Try blowing through it. If you can’t, try passing a small piece of wire through to dislodge the carbon trapped inside, causing the error code you’re experiencing. If you notice some water blown out, this could be the cause of the code.
If the tube is clear and free, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear corroded, burned, or perhaps greenish compared to the normal metallic color you’re used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If that’s not possible, find 91% rubbing alcohol and a light plastic-bristled brush to clean them. Then let them air dry, get some dielectric silicone compound (same as used for bulb sockets and spark plug wires), and apply it where the terminals make contact. Then, ensure the tube connecting the turbocharger to the intake manifold is not leaking. Visually inspect all tube connections around the turbocharger and intake manifold. Tighten all hose/band clamps.
If you have a scan tool, clear the diagnostic codes from memory and see if this code returns. If it doesn’t, the connections were likely your problem.
If the code returns, we’ll need to test the sensor and its associated circuits. Typically, there are 3 wires at the exhaust pressure sensor.
Disconnect the harness going to the exhaust pressure sensor. With a digital voltmeter (DVOM), test the 5V supply circuit going to the sensor to ensure it’s powered (red wire to the 5V supply circuit, black wire to a good ground). If there are 12 volts at the sensor when there should be 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts, or possibly a faulty PCM.
If that’s okay, with a DVOM, check that the exhaust pressure sensor signal circuit is 5V (red wire to the sensor signal circuit, black wire to a good ground). If there is no 5 volts at the sensor, or if you see 12 volts at the sensor, repair the wiring from the PCM to the sensor, or again, a possible faulty PCM.
If that’s okay, check that the exhaust pressure sensor is properly grounded. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the exhaust pressure sensor circuit ground. If the test light does not light up, this would indicate a circuit problem. If it lights up, wiggle the wiring harness going to each sensor to see if the test light flickers, indicating an intermittent connection.
If all tests have passed so far and you continue to get a P047B code, this would most likely indicate a failing exhaust pressure sensor, although a faulty PCM cannot be ruled out until the sensor has been replaced.