Technical Description of OBD-II Trouble Code
Exhaust Pressure Control Valve “A”
What is the meaning of this code?
This generic powertrain/engine diagnostic trouble code is typically applicable to diesel engines, including certain Ford, Dodge, Mercedes, Nissan, and VW vehicles.
This code can also apply to trucks equipped with diesel engines and dealer-installed exhaust brakes.
An exhaust pressure control valve is placed in the exhaust stream after the exhaust manifold to generate heat in the form of back pressure in the exhaust. This heat and/or back pressure can be used to assist in cold start warm-up. It can also be used to oppose cylinder pressure coming from the engine cylinders out of the exhaust, thereby slowing down the engine and the vehicle, which is particularly useful during towing operations.
This code specifically relates to the output circuit to the exhaust pressure control solenoid. It is considered to be an electrical circuit fault only.
Troubleshooting steps may vary depending on the manufacturer, type of exhaust back pressure control, and wire colors to the control solenoid.
Symptoms
Symptoms of a P0475 engine code may include:
Potential Causes
The typical causes for this code to set are:
Diagnostic and Repair Procedures
A good starting point is always to search for a technical service bulletin (TSB) for your particular vehicle. The vehicle manufacturer may have a PCM flash/reprogram to address this issue, so it’s worth checking before going down a potentially incorrect path.
Next, locate the Exhaust Pressure Control Solenoid on your particular vehicle. Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burn spots, or melted plastic. Pull the connectors apart and carefully inspect the terminals (the metal parts) inside the connectors. Check if they appear corroded, burnt, or possibly green in color instead of the normal metal color. If needed, you can 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 where the terminals come into contact.
If you have a scan tool, clear the diagnostic trouble codes from memory and see if this code returns. If it does not, then the connections were most likely the problem.
If the code does return, you will need to test the solenoid and its associated circuits. Typically, there are 2 wires at the Exhaust Pressure Control Solenoid. First, disconnect the harness going to the solenoid. With a Digital Volt Ohm Meter (DVOM), connect one lead of the meter to one terminal of the solenoid and the remaining lead to the other solenoid terminal. The resistance should not be open or shorted. Verify the resistance specifications for your particular vehicle. If the solenoid is either open or shorted (infinite resistance or no resistance/0 ohms), replace the solenoid.
If that’s okay, use a DVOM to check if you have 12V on the Exhaust Pressure Control Solenoid power supply circuit. Connect the red lead to the solenoid power supply circuit and the black lead to a good ground. Ensure that the ignition is on. If there is no 12 volts to the solenoid or if there is 12 volts when the ignition is turned off, repair the wiring from the PCM or relay to the solenoid, or possibly replace a faulty PCM.
If that’s okay, check if you have a good ground at the Exhaust Pressure Control Solenoid. Connect a test light to 12V battery positive (red terminal) and touch the other end of the test light to the ground circuit going to the solenoid. If the test light does not light up, this indicates a problem with the circuit. If it does light 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 P0475 code, this most likely indicates a failed Exhaust Pressure Control Solenoid, although a failed PCM cannot be ruled out until the solenoid has been replaced.
