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Error Code P0475 is defined as Exhaust Pressure Control Valve “A”, meaning there’s something wrong with the exhaust back pressure valve.
This code is a generic trouble code and typically applies to diesel engines, including but not limited to certain models of Ford, Dodge, Mercedes, Nissan, and VW vehicles.
Error Code P0475 refers to a problem in the exhaust back pressure valve, which could be caused by more than one problem. One is a defective exhaust back pressure valve, and two is the shorted out or open exhaust back pressure valve. It can also be caused by a poor electrical connection on the exhaust back pressure valve.
As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other symptoms include:
- Engine lacks power
- Lacks engine braking
- Cold engine warmup time is longer than usual
As said earlier, this code is typically caused by problems in the exhaust back pressure valve, which could be:
- Power supply short to power between exhaust pressure control solenoid and the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes)
- Open in the power supply circuit between the PCM and exhaust pressure control solenoid
- Short to ground in the power supply circuit to the exhaust pressure control solenoid
- Defective exhaust pressure control solenoid
- Failed PCM (rare)
How to Check
A good starting point for any error code is always through TSB (Technical Service Bulletin) search for the particular vehicle. The vehicle manufacturer may have a PCM flash/reprogram to cover this issue, and it pays to check on this before you find you’ve gone down a long/wrong path.
Next step is to find the Exhaust Pressure Control Solenoid on the vehicle and inspect its connectors and wirings. Look for signs of damage such as chafing, bare spots, burn wires, rubbing, or melted plastic. The connectors must be pulled apart to check their terminals (the metal parts) inside the connectors. Check if there are any signs of corrosion, burnt, or wires that are possibly green in color versus the normal metal color you normally see from the others. The terminals can be cleaned using an Electrical Contact cleaner or 91% rubbing alcohol and light plastic bristle brush to clean the terminals thoroughly. They should be dried, and a dielectric silicone compound must be used to put terminals into contact (this is the same stuff used for spark plug wires and light bulb sockets).
A scan tool must be used to clear the codes off of the vehicle’s memory and to see if the code comes back. If it does NOT come back, then it’s a case of faulty connections.
If the code comes back, however, the solenoid and its circuits must be tested. Usually, the Exhaust Pressure Control Solenoid comes with two wires. The wire that connects the harness going to the exhaust pressure control solenoid must be disconnected first.
A DVOM (digital volt/ohmmeter must be connected to one lead of the meter and one lead of the solenoid terminals. The other must be connected to the other lead to the other solenoid terminal. Note that this should not be open or shorted.
Next, the vehicle must be check for resistance. If the solenoid is either open or shorted, then it must be replaced.
Next, check whether there is a 12V on the Exhaust Pressure Control Solenoid power supply circuit. Make sure the ignition is on. If there is no 12V to the solenoid, or there is 12V when the ignition is turned off, you will need to relay to the solenoid or repair the wiring to the PCM.
In some cases, the problem could be caused by a bad PCM, but if it’s not the case (as with most cases), make sure you have a solid ground at the Exhaust Pressure Control Solenoid by connecting a test light to a 12V battery positive (red terminal) and touch the other end of the test light to the ground circuit that goes to the Exhaust Pressure Control Solenoid circuit ground. It id does NOT light up, the problem is in the circuit. If it DOES light up, check the wiring harness by shaking, if the light flickers, then the problem is an intermittent connection.
EBP (Exhaust Back Pressure) device can detect problems with this code. Some mechanics also choose to use the tube between the exhaust manifold and EBP sensor with an exhaust back pressure step test. This is when the PCM commands and then measures a specified pro-programmed pressure.
If then PCM determines a time for pressure decay during the engine running test.
If the PCM detects an EBP, Intake Air Temperature or Engine Oil Temperature sensor fault, the PCM will disable the exhaust back pressure regulator. This is to determine how the exhaust pressure control valve malfunction and what exactly is causing it.
How to Fix
- Cleaning, repair or replacement of faulty connections and terminals
- Repair or replacement of a faulty solenoid
- Repair of PCM wiring
- Repair and reprogram PCM (rare)
If the vehicle can pass all of these tests and is still receiving a P0475 code, you probably have a failed Exhaust Pressure Control Solenoid.