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Error Code P047F is defined as Exhaust Pressure Control Valve A Stuck Open.
This code is a generic trouble code, meaning it typically applies to all vehicles equipped with the OBD-II system, which includes models from makes like Chevrolet, Dodge, Ford, Honda, VW, etc. Though generic, the exact steps for diagnosis and repairs may vary from one make, model, and powertrain configuration of the vehicle.
When Error Code P047F is stored, that means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has detected a problem in one of the exhaust pressure control (regulator) valves. Valve “A” refers to a problem in the bank of the engine that contains the #1 cylinder, which usually means the valve is stuck in the open position. Designs, of course, may vary from one manufacturer to another.
The Exhaust Pressure (a.k.a. back pressure) regulators are used in both turbocharged gasoline and diesel engines. Exhaust Back Pressure Control Valve operation is usually similar to the throttle body. It’s equipped with an electronically plate to restrict the exhaust flow, as set by the PCM. There is also an exhaust back pressure control valve position sensor and exhaust back pressure sensor.
To raise the temperature of both the engine and engine coolant faster, an increase exhaust back pressure is used. This could come in handy in very cold climates.
When the PCM detects that there’s a cold air intake temperature that is lower than the minimum threshold, it will activate the exhaust back pressure valve operation to and keep it until the intake air temperature has been normalized. The activation of the exhaust back pressure regulator only happens once every ignition cycle. The exhaust back pressure control valve is designed to park in the wide open position once the PCM deactivates it.
If the PCM detects that there’s an exhaust back pressure regulator that is outside of its desired position, or if the exhaust back pressure sensor is out of position, then it will set the Error Code P047F.
As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms include:
- Delayed engine warm-up
- Diminished engine performance
- Engine stumbles or stalls when cold
- May come with other related Exhaust Back Pressure codes
Common causes for this code include:
- Defective exhaust pressure sensor
- Defective exhaust pressure control valve
- Defective exhaust pressure control valve position sensor
- Open or shorted wiring in one of the exhaust pressure control valve circuits
How to Check
A vehicle information source will be needed to diagnose this code. Other important tools needed include:
- Diagnostic scanner
- Digital volt/ohmmeter (DVOM)
- Infrared thermometer with laser pointer
Diagnosis starts with a thorough visual inspection of the connectors and wirings of the related components. Then, connect the scanner to the port to retrieve all stored codes and freeze frame data. It is important to take note of this information as you go through with the diagnosis.
Next, clear the codes and then take the vehicle for a test drive to see if the code returns. If there are intake air temperature or engine coolant temperature codes present, then diagnose and repair those codes before continuing with the P047F.
Check the TSB (Technical Service Bulletin) for the vehicle and take note of the symptoms.
- If there are no issues with the connector and wiring, then use the DVOM and proceed on testing the expected voltage signal at the exhaust pressure control valve. You may have to use the scanner to simulate a cold start condition and to activate the exhaust pressure control system.
- If the right voltage or ground signal is not discovered at the exhaust pressure control valve connector, disconnect all related controllers and use the DVOM to test the individual circuit resistance, as well as continuity. Non-compliant circuits must be replaced, if not repaired.
- If the exhaust pressure control valve and circuits are still functioning well, then proceed on testing the exhaust pressure control valve position sensor, or exhaust pressure sensor (if applicable) according to the specifications set by the manufacturer. Replace all failed components if necessary.
How to Fix
Common repairs include:
- Repair or replacement of damaged connectors or wirings
- Repair or replacement of non-compliant circuits
- Replacement of failed components in the exhaust pressure control valve
If there is no scanner data display available, then you can use the infrared thermometer to get the actual exhaust temperature reading. This could prove helpful to determine whether the exhaust pressure control is working or not. It can also detect a valve that is stuck in either the open or closed position.
Also, note that the defective catalytic converter or muffler will NOT cause the P047F code.
Note that exhaust pressure control systems are mostly used in turbocharged/supercharged applications.