Technical Description of OBD-II Trouble Code
Malfunction in the Exhaust Pressure Sensor
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, then extended to all Ford EcoBoost engines, and eventually included 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 still possible to encounter this code in a VW or other make.
This code specifically focuses on 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 P0471 may also be present simultaneously with P0470. 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.
A typical exhaust pressure sensor:
Related trouble codes for the exhaust pressure sensor:
Symptoms
The symptoms of a P0470 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 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 is worth checking before going down a potentially lengthy and incorrect path.
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 it. If unable to do so, attempt to dislodge the trapped carbon inside by running a small piece of wire through it. 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 (the metal parts) inside. Check for signs of corrosion, burning, or a greenish color instead of the normal metal color. 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 (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 all hose/band clamps as needed.
If you have a scan tool, clear the diagnostic trouble codes from memory and see if this code reappears. If it does not, then the issue was most likely related to 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 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 that checks out, use a DVOM to verify that 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 that is also fine, check for a good ground 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 going to the Exhaust Pressure Sensor. If the test light does not illuminate, it indicates a problem with the circuit. If it does illuminate, wiggle the wiring harness going to each sensor to see if the test light flickers, indicating an intermittent connection.
If all the tests have been passed so far and you continue to receive a P0470 code, it most likely indicates a failed Exhaust Pressure sensor. However, a failed PCM cannot be ruled out until the sensor has been replaced.
