P049F Exhaust gas pressure control valve B
Content
P049F Exhaust gas pressure control valve B
OBD-II DTC Datasheet
Exhaust gas pressure regulating valve "B"
What does this mean?
This Generic Transmission / Engine DTC usually applies to diesel engines including, but not limited to, certain Ford, Dodge, Mercedes, Nissan, and VW vehicles.
This code can also apply to trucks equipped with diesel engines and dealer-installed exhaust brakes.
A valve is placed in the exhaust stream downstream of the exhaust manifold to generate heat in the form of back pressure in the exhaust. This heat and / or back pressure can be used to warm up during a cold start. It can also be used to counteract the pressure in the cylinders emanating from the engine's cylinders from the exhaust gases, thereby slowing the engine and the vehicle along with it. This is especially useful when towing.
This code is strictly for the exhaust pressure control solenoid output circuit. This code is considered a fault in the electrical circuit only.
Troubleshooting steps may vary depending on the manufacturer, the type of exhaust back pressure regulator and the colors of the wires to the control solenoid. Consult your specific vehicle repair manual to determine which valve "B" is for your particular application.
symptoms
Symptoms of a P049F engine code may include:
- Malfunction Indicator Lamp (MIL) illuminated
- Lack of power
- No engine braking
- Longer than usual warm-up time for a cold engine
Possible Causes P049F
Usually the reason for installing this code is:
- Short circuit to + battery in the power circuit between the exhaust pressure control solenoid and the PCM (transmission control module)
- Open in the power circuit between the exhaust pressure control solenoid and the PCM
- Short circuit on weight in the power supply circuit of the solenoid of pressure regulation of exhaust gases
- Defective exhaust gas pressure control solenoid
- PCM may have crashed (unlikely)
Diagnostic and repair procedures
A good starting point is always to find a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a flash memory / PCM reprogramming to fix this problem and it's worth checking it out before you find yourself on the long / wrong path.
Then locate the “B” exhaust pressure control solenoid valve on your specific vehicle. Once detected, visually inspect the connectors and wiring. Look for scuffs, scuffs, exposed wires, burn marks, or molten plastic. Disconnect the connectors and carefully inspect the terminals (metal parts) inside the connectors. See if they look rusty, burnt, or perhaps green compared to the usual metallic color you're probably used to seeing. If terminal cleaning is required, you can purchase electrical contact cleaner at any parts store. If this is not possible, find 91% rubbing alcohol and a light plastic bristle brush to clean them. Then let them air dry, take a dielectric silicone compound (the same material they use for bulb holders and spark plug wires) and place where the terminals make contact.
If you have a scan tool, clear the diagnostic trouble codes from memory and see if the code returns. If this is not the case, then there is most likely a connection problem.
If the code returns, we will need to test the solenoid and associated circuits. Typically, 2 wires are connected to the exhaust gas pressure control solenoid. Disconnect the harness from the exhaust pressure control solenoid first. Using a digital volt ohmmeter (DVOM), connect one lead of the meter to one terminal of the solenoid. Connect the remaining meter lead to the other terminal of the solenoid. It must not be open or short-circuited. Check the resistance characteristics for your specific vehicle. If the solenoid is open or shorted (infinite resistance or no resistance / 0 ohms), replace the solenoid.
If this is normal, with the DVOM, make sure you have 12V power to the exhaust pressure control solenoid (red wire to the solenoid power circuit, black wire to good ground). Make sure the ignition is on. If the solenoid is not 12 volts, or if there is 12 volts with the ignition off, repair the wiring from the PCM or relay to the solenoid, or possibly a faulty PCM.
If normal, check that the exhaust pressure control solenoid valve is properly grounded. Connect a test lamp to the 12V battery positive (red terminal) and touch the other end of the test lamp to the ground circuit that leads to the exhaust gas pressure control solenoid circuit ground. If the test lamp does not light up, it indicates a faulty circuit. If it does light up, wiggle the wire harness going to each sensor to see if the test lamp blinks, indicating an intermittent connection.
If all tests have passed so far and you keep getting a P049F code, it will most likely indicate a faulty exhaust pressure control solenoid, although a failed PCM cannot be ruled out until the solenoid is replaced.
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