P049F OBD Error Code: Problem & Solutions

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Here’s the most generic error you will come across with your vehicle engine, the OBD Code P049F is one of the most commonly found errors. So, take a deep breath and read on, to know more about the OBD-II code P049F and how to fix it!

The OBD-II Code P049F Powertrain Control Module (PCM) failure is known as Exhaust Pressure Control Valve - B. The back pressure during engine warm-up is controlled by the Exhaust Pressure Control Valve. When there’s an incorrect signal received from this Exhaust Pressure Control Valve, the PCM will set code P049F.

The Exhaust Back Pressure Regulator controls the exhaust back pressure, this is essential for cars that run in cold and ambient temperatures. It is a variable position valve and helps in increasing the car heat and decrease the time required to defrost the windshield. The Engine Control Module (ECM) uses few components to determine the exhaust back pressure. These are; the measured exhaust back pressure, temperature of the engine oil and of (ambient) intake air and engine load. The valve position is controlled by switching the output signal circuit. It is brought to 12 volts inside the ECM, and the on/off time is adjusted from 0 to 99% depending on the desired exhaust back pressure. When the engine is started, the ECM works the exhaust back pressure valve and commands it to switch on and off one time. When the engine is started, if the Intake Air Temperature (IAT) senses the temperature of the intake air to be < 37° F (5°C) and the sensed oil temperature by the Engine Oil Temperature (EOT) sensor ranges from 32°-140°F (0-60°C), then it will continue keeping the back-pressure valve partially closed. As and when there is a rise in the oil temperature during engine operation, the ECM will respond by controlling the valve in correlation to the rising temperature of oil.

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

• A short circuit between the exhaust pressure control solenoid and the Powertrain control module (PCM)
• An open in the power supply circuit, typically between the Powertrain Control Module (PCM) and the exhaust pressure control solenoid
• Short circuit to the ground in the power supply circuit connected to the exhaust pressure control solenoid
• Faulty Exhaust Pressure Control Solenoid
• Failed PCM (highly unlikely)

1. Exhaust Pressure Control Valve - The EPC valve helps measure the pressure of the exhaust gasses. Chances are it’s not working properly and needs a repair or replacement.
2. Powertrain Control Module - The PCM is the brains of your vehicle system, buy at Parts Avatar and get free shipping for orders over $99.
3. Engine Control Module - Your cars ECM controls the fuel mixture, ignition timing, variable cam timing and emissions control. Only the best quality should be used for this important job. Parts Avatar provides superior quality car parts for variety of vehicle models.
4. Exhaust Pressure control Solenoid - Has to be in good working condition to perform best. Check and replace it if necessary.

It is essential 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 P049F here:

Common Symptoms

• Illuminated Malfunction Indicator Lamp (MIL)
• Poor or absence power
• Poor or absence of engine braking
• Unusually longer time needed to warm-up cold engine

Read on to find out how you can correct the OBD Code P049F.

There is no need to be anxious as Parts Avatar – Car Parts Online, is here to help you out! We have high grade auto parts that can eliminate all issues. Quality is our priority. Here’s a list of parts that you may require to correct the engine error OBD Code P049F

• Exhaust Pressure Control Valve
• Powertrain Control Module
• Engine Control Module
• Exhaust Pressure Control Solenoid

You can purchase these parts on our website with easy 30-day return policy. Track your order and be updated on its arrival. We also offer priority shipping (your order shipped overnight). Don’t compromise on quality, fix your vehicle and become stress free!

Following are some steps which you should follow in order to diagnose this P049F fault code:

Start off with a technical service bulletin (TSB) search for the specific vehicle you are looking to diagnose. Majority of the vehicle manufacturers will have a PCM flash/reprogram that covers this issue. It’s always good to refer it, in order to diagnose the problem quickly and accurately.

The next step would be to locate the “B” Exhaust Pressure Control Solenoid in that specific vehicle. Once it is located, you proceed to visually inspecting the connectors and the wiring. What you’re mainly looking for is any chafing, rubbing, bare wires, burn spots or meltic plastic of the parts in and around the Exhaust Pressure Control Solenoid. At this point, you can pull the connectors apart carefully and inspect the metal parts aka terminals present inside the connectors. Inspect for any corrosion, pay attention to any burt or even green colour of the metal as opposed to the normal metal colour you’re used to seeing. If you feel the need to clean up the terminals, use some Electrical Contact cleaner, which is readily available at any parts store. A light plastic bristle brush and 91% rubbing alcohol should do the job if getting the electrical contact cleaner isn’t possible. Let the cleaned parts dry, procure some dielectric silicone compound (it’s the same as use for light bulb sockets and spark plug wires) and apply where the terminals come into contact.

Use a scan tool, if you have one and clear the diagnostic trouble codes from the memory. Wait and see if the code reappears. If it doesn’t then it’s mostly a problem with the connections. However, if the code does return, the next step would be to test the solenoid and circuits associated to it. There are typically 2 wires found at the Exhaust Pressure Control Solenoid. Start off with disconnecting the harness headed to the Exhaust Pressure Control solenoid. Use a Digital Volt Ohm Meter (DVOM), and connect one lead of the meter to one terminal of the solenoid, connect the remaining meter lead to the other solenoid. Ensure that it’s not open or shorted. Check your specific vehicles resistance specifications. If the solenoid is found to be shorted or open i.e. showing infinite resistance or no resistance/0 ohms then replace the solenoid.

If there's no problem there, then use the DVOM to ensure you have 12V on the Exhaust Pressure Control Solenoid power supply circuit (Black lead to a good ground and the red lead to the solenoid power supply circuit). If there is 12 volts when the ignition is off or no 12 volts to the solenoid, then the repair of the wiring from the PCM or relay to the solenoid is required. There is also a possibility of a bad PCM. If that is also okay, then ensure that you have a good ground at the Exhaust Pressure Control Solenoid. You will now have to connect a text light to a 12V battery positive ie the red terminal, and the other light would have to be touched to the ground circuit which will be going to the Exhaust Pressure Control Solenoid ground circuit. Observe the test light, if it doesn't light up, it is indicative of a problem in the circuit. It lights up, then wiggle the wiring harness that is going to each transmission sensor. Note if the test light flickers, this would indicate an unstable connection.

Now, if the OBD Code P049F still appears have clearing all other tests, then it’s likely an indicative of a failed Exhaust Pressure Control Solenoid. However, unless the solenoid isn’t replaced one can’t rule out if the PCM has failed.

Common Mistakes When Diagnosing the P049F Code

• Failure of Exhaust pressure control valve
• Failure of Powertrain Control Module (PCM)
• Problem with wiring