Guide To P04A0 OBD Error Code Solutions

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What is OBD code P04A0? What are its symptoms and how they can be rectified? Keep reading. OBD-II Code Powertrain Control Module (PCM) refers to the failure in the Exhaust Pressure Control Valve "B" Range/Performance

The Exhaust Pressure Control Valve has the ability to control the exhaust back pressure during an engine warm up. If the engine control module, detects an incorrect signal in the Exhaust Pressure Control Module, then the PCM will show the OBD error code P04A0.

Exhaust Back Pressure Regulator is a valve which helps to control the back pressure during the time of cold ambient temperature so that you can increase the heat of the cab and decrease the amount of time that is needed to defrost the windshield. In order to determine the exhaust back pressure, the Engine Control Module (ECM) uses the intake air temperature, oil temperature of the engine, load of the engine and the measured exhaust back pressure, (ambient). You can control the position of the value, if you switch the output signal of the circuit to 12 volts that is present inside the ECM.

Similarly, you can also modulate the on/Off time from 0 to 99% depending on your desired exhaust back pressure. During each of the initial start-up of the engine, the ECM commands the valve to cycle on and off it for one time, by exercising the exhaust back pressure valve. During the start-up, if the Intake Air temperature (IAT) senses an intake air which is which is lesser than 37°F (5°C) and if the Engine Oil temperature (EOT) senses the oil temperature which is between 32°-140°F (0-60°C), then the back-pressure valve will remain partially closed. During an engine operation, if the temperature of the oil increases, then the ECM will continue to control the valve in response to the increase of the oil temperature.

What causes this problem with the Exhaust Pressure Control Valve "B" Range/Performance?

• Immovable Exhaust Back Pressure Valve
• Probability of a misadjusted/ held /broken turbocharger wastegate
• A leak in the Exhaust Gas Pressure Sensor/ Restriction in the Exhaust system
• Failure of the PCM (highly not possible)

1. Powertrain Control Module - Failure of the powertrain control module can give rise to Error code P04A0. Replace them as soon as possible.
2. Exhaust Pressure Control Valve - Do you detect any leak in the exhaust pressure control valve? Then it’s high time you replace them soon.
3. Exhaust Gas Pressure Sensor - Don’t just wait. Get the exhaust gas pressure sensor for your make from us at affordable cost.
4. Engine Control Module - Is there a fault in your Engine Control Module? Looking for a right place to get your replacement parts? Parts Avatar has the parts for every make.

It is vital to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P04A0 here:

Common Symptoms

• Malfunction Indicator Lamp (MIL) that is well-lit
• Short supply of power
• Deficiency of engine braking
• Warmup time of the cold engine which is longer than usual

Want to correct the Trouble Code P04A0? Read these points mentioned below:

• Replacement of the powertrain control module
• Frequent cleaning of the exhaust pressure control valve/ Exhaust Gas pressure sensor
• Replacing the Engine Control module

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It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P04A0 code to be stored:

• You can always start with the search of technical service bulletin (TSB) for your particular vehicle. The vehicle manufacturer can resolve this issue with the help of a PCM flash (Powertrain Control Module) or a reprogram. It is always good to check for this check in the beginning before you go a long way down the wrong path.
• Next, check if there are any exhaust leaks. You can also check for the exhaust noises coming from pipes, exhaust manifolds, and or any black soot in the area of the leak. If you find any leak, then repair the exhaust leak right away.
• Your next step is to locate the “B” Exhaust Pressure Sensor on your specific vehicle. Once you locate it, check for the proper connection of wires and connectors if there are any burn spots, chafing, rubbing, or any plastic that is molten. Separate the connectors carefully and inspect the terminals that is the metal parts which is inside the connector. Look if the inside of the metal is burnt, corroded or green in colour rather that the green colour which you will usually see. If you have to clean the terminals then try getting an electrical contact cleaner in any automobile parts store. If it doesn’t work out, then you can clean them with a light plastic brush and some 91% rubbing alcohol. Allow them to dry for some time. Get a small amount of dielectric silicone compound (material which is used for the wires of spark plug and light bulb sockets) and apply them at the area, where the terminals come in contact with one another.
• Also, if your tube is well-fit then you have to remove the sensing tube which connects the exhaust manifold from the exhaust back pressure sensor.
• Try clearing the diagnostic trouble codes from the memory with the help of a scan tool and check if the code returns. If the error does not return, then the problem was mainly because of the connection.
• But if the code returns, then you will have to verify the proper functioning of turbocharger boost operation. In order to read the turbocharger boost pressure, you will need a scan tool. You will receive the same information from the intake manifold pressure. When the key is on note down the pressure, but make sure that the engine is off. After you start the engine, start driving the vehicle at a safe speed. Now you have to accelerate the engine to a wide-open throttle and make sure that the RPM of the engine does not cross 2500-3000 RPM’s. You will possibly note a change of 18 PSI or more depending on manufacturer of the vehicle and the year when the vehicle was manufactured. Upon boosting the pressure, if you do not obtain 18 PSI, then you will see the indications of an immovable or faulty wastegate, restricted exhaust or most probably a fault in the turbocharger.
• If you pass this test or if you are unable to check with the boost of the turbocharger, then you will have to test the sensor and all the circuits associated with it. The exhaust pressure sensor basically has three wires.
• Disconnect the wire that leads to the exhaust pressure sensor. Now test the circuit which has 5V power supply with the help of a Digital Volt Ohm meter (DVOM) with the help of a sensor in order to ensure that it is powered up (Connect the Red lead to the 5-volt power supply, and the black lead to
• the ground). If the sensor detects 12 Volts instead of 5 volts, then you have to repair the wire from the PCM to the sensor to fall to 12 Volts or it will possibly be a bad PCM.
• If everything is fine with DVOM, then you have to check that the exhaust pressure sensor signal has 5V on it (Connect the red lead to the signal sensor of the circuit, and connect the black lead to the ground). If you do not see 5 Volts on the sensor or if there is 12 Volts in the sensor, you have to again repair the wires from PCM to sensor or it can again be a bad PCM.
• If everything is OK, make sure that the exhaust pressure sensor is connected to a good ground. Take a 12 Volt battery that is positive and connect it to the test light (red terminal) and now connect the other end of the test light to the ground circuit which leads to the ground of exhaust pressure sensor circuit.
• If that’s OK, check to make sure you have a good ground at the Exhaust Pressure sensor. 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 Exhaust Pressure Sensor circuit ground. If the test light does not light up, this would indicate the problem circuit. If the light turns on, shake the wire joint that leads to exhaust pressure sensor in order to check for the flickering of the test light which indicates that the connection is broken.
• If you have passed all the test and still the P04A0 code keeps showing up, then it indicates the failure in the exhaust pressure sensor. Although, you cannot ignore the PCM, until and unless the sensor is replaced.

Common Mistakes When Diagnosing the P04A0 Code

Here are a few of the common mistakes that you will come across, when you diagnose the P04A0 code:

• Failure of the Exhaust pressure control valve
• Failed Powertrain Control Module (PCM)
• Issues with wires