P04A6 OBD Error Code: Problem & Solutions

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Diagnostic trouble code P04A6 is defined as Exhaust Pressure Control Valve B Position Sensor/Switch Circuit. It indicates that there is a malfunction in the exhaust pressure control valve circuit. The Exhaust Pressure Control Valve controls exhaust back pressure during engine warm up and when PCM diagnose that there is an incorrect signal from the exhaust pressure control valve, it will store code P04A6.

OBD II Code P04A6 is technically described as Exhaust Pressure Control Valve "B" Position Sensor/Switch Circuit where in "B" indicates the problem is with a portion of the system circuit, instead of a particular symptom or component. This generic powertrain diagnostic trouble code (DTC) typically applies to all OBD-II vehicles equipped with an exhaust pressure control valve sensor or switch. Due to this trouble code you may start facing problems like Difficulty in starting your vehicle, enhanced emissions and poor performance of engine. PCM monitors the Exhaust Pressure Control Valve Position Sensor. The PCM sets the OBDII code when the Exhaust Pressure Control Valve Position Sensor is not to factory specifications.

Code P04A6 is set when the PCM detects a malfunction in the exhaust pressure control valve circuit.

What causes this problem with the Exhaust Pressure Control Valve "B" Position Sensor/Switch Circuit?

• Problem with wiring and connections
• Frayed exhaust pressure control valve
• PCM failure

1. Powertrain Control Module - The Powertrain Control Module PCM is an on-board electronic control unit that primarily controls the charging, emission and transmission systems of the vehicle. PCM should work properly as it is a brain for your vehicle, if you discover any faults get it fixed as soon as possible.
2. Exhaust Pressure Control Valve - Exhaust pressure control valve operation is often similar to that of the throttle body. It uses an electronically controlled plate to restrict exhaust flow as determined by the PCM. Faulty exhaust pressure control valve will not let your vehicle to run smoothly so repair or replace the faulty one at earliest.
3. Exhaust Pressure Sensor - The exhaust pressure sensor is present in the exhaust manifold outlet of the exhaust system. Make sure it should work efficiently to avoid all the associated trouble codes.

Below mentioned are some common symptoms that can help you to identify this code:

• Decreased engine performance
• Increased emissions
• Problem while starting
• Illuminated check engine light

To avoid major problems and major expensive repairs, it is better to fix the stored trouble codes as soon as possible. If you fix the error code at initial stage that will be beneficial for your vehicle as well as for your pocket. Following repairs and replacements can help you fix this code:

• Inspect the exhaust pressure control valve carefully; if you discover it faulty replace it.
• Repair or replace the damaged and corroded wiring and connectors.
• Look for open and shorted circuits, repair or replace them immediately.
• Replace the faulty PCM.

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Steps to diagnose this code are as follows:

• Begin with the visual inspection of exhaust pressure control valve and the related wiring.
• Repair all the loose wiring, damaged connectors if you discover them faulty.
• Test the solenoid by using digital multimeter. If the meter displays a reading out of specification or out of limits (OL) indicating an open circuit, the solenoid should be replaced.
• Check The Power Side of the Circuit for this check if any power coming out of the PCM.
• Check the ground portion of the circuit, Remove the solenoid connector. Connect the meter between the solenoid ground terminal and chassis ground. If the meter reads a numeric value, there is continuity. If the meter reads out of limits (OL) there is an open circuit between the PCM and solenoid that will need to be located and repaired.

Common Mistakes When Diagnosing the P04A6 Code

The most common mistake while diagnosing this code is directly replacing the exhaust pressure control valve without even diagnosing it carefully wherein the responsible component was not