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Error Code P0476 is defined as Exhaust Pressure Control Valve “A” Range/Performance.
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. It can also apply to trucks with diesel engines and dealer installed exhaust brakes.
To generate heat in the form of back pressure in the exhaust, a valve is placed in the exhaust stream, after the exhaust manifold. This is essential for cold start warm up, and to oppose cylinder pressure coming from the engine cylinders out of the exhaust, thereby, slowing the engine down and the vehicle along with it. This can be extremely useful during towing operations.
During the exhaust pressure step test, the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) commands and measures a preprogrammed exhaust pressure, and then measure the time for pressure decay during the vehicle’s engine running test.
The exhaust back pressure step test will recognize any problems, with the EBP (exhaust back pressure) device, or the tube that sits between the exhaust manifold and the EBP sensor. If the PCM determines a fault in the EBP, IAT (Intake Air Temperature), or EOT (Engine Oil Temperature) sensors, then it will disable the EBP regulator which will trigger the Error Code P0476.
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:
- Lack of engine power
- Lack of engine braking
- Engine warm-up time taking longer than normal
The most common cause of Error Code P0476 is faulty Exhaust Back Pressure valve. Other common causes include open or shorted Exhaust Back Pressure valve harness or poor electrical connection in the Exhaust Back Pressure valve.
Other possible causes can include:
- Stuck Exhaust Back Pressure Valve
- Possibly stuck/damaged/misadjusted turbocharger wastegate
- Exhaust system restriction/leaks
- Exhaust Gas Pressure Sensor
- Failed PCM (highly unlikely)
How to Check
The exhaust back pressure regulator is a variable position valve which controls the exhaust back pressure during times of cold temperature. It increases the vehicle’s cab while also decreasing the amount of time required to defrost the windshield. The PCM uses the vehicle’s measured exhaust back pressure, intake air temperature, engine oil temperature, and engine load, to determine how much exhaust back pressure is required.
You can control the valve positioning of your vehicle by switching the output signal circuit in your PCM to 12V. During engine start and the temperature of intake air on the IAT sensor is less than 37°F (5°C), and the oil temperature is between 32°-140°F (0-60°C), the vehicle will continue to keep back pressure valve partially closed. As the oil temperature rises as your engine runs, your ECM will adjust the valve in response to the rising oil temperature.
The temperature of the oil increases as the engine runs, the PCM will adjust the valve in response to the increase in oil temperature.
These are the many areas mechanics will examine. Technicians use advanced diagnostic equipment that ordinary vehicle owners may not have access to. This is why it’s important to take your vehicle to a trained, well-equipped, and certified professional.
How to Fix
Since this code can be caused by several problems, it is important to run a thorough diagnostic test before conducting any repairs. With that said, the common repairs would include:
- Replacement of torque converter
- Cleaning of port to the right side of the exhaust manifold
- Repair or replacement of malfunctioning cam sensor (when vehicle is struggling when you put into gear)
It is best to start with small and minor repairs when addressing this code. If these fixes do not provide a solution, you can start with larger tasks, such as replacement of faulty components.
Error Code P0476 can be a serious problem, especially when the vehicle stalls constantly or not start. Thus, your best option is to leave the problem to trained technicians and have them solve the problem for you.