What does it mean?
This generic powertrain/engine diagnostic code generally applies to turbocharged and supercharged engines, including but not limited to some Audi, Ford, GM, Mercedes, Mitsubishi, VW, and Volvo vehicles.
The Powertrain Control Module (PCM) controls the boost pressure in a gasoline or diesel engine by controlling the output circuit to the “B” wastegate/boost control solenoid.
Depending on how the manufacturer activates the solenoid, when the PCM provides power or ground to energize the solenoid and the PCM notices that there is no voltage in the circuit at any time when there should be (de-energized), the PCM will set the P0249 code. This code is considered an electrical circuit fault only.
Troubleshooting steps may vary depending on the manufacturer, the type of wastegate/boost pressure control, and the color of the control solenoid wires.
Symptoms
Symptoms of a P0249 engine code may include:
Malfunction Indicator Light (MIL) illuminated
Instrument cluster message alerting the driver to the condition
Lack of power
Causes
Possible causes for setting this code are as follows:
Open in the control circuit (ground circuit) between the wastegate/boost control solenoid B and the PCM
Open in the power supply circuit between the wastegate/boost control solenoid B and the PCM
Short to ground in the power supply circuit of the wastegate/boost control solenoid B
Wastegate/boost pressure control solenoid B
Possibly a failed PCM (highly unlikely)
A good starting point is always to check the Technical Service Bulletins (TSBs) for your particular vehicle. Your problem may be a known issue with a known fix released by the manufacturer and can save you time and money when diagnosing.
Next, locate the “B” wastegate/boost control solenoid on your particular vehicle. Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they look burned or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if cleaning the terminals is necessary. Let it dry and apply electrical grease where the terminals make contact.
The most common failure is due to connection problems.
If you have a scan tool, clear the diagnostic codes from the memory and see if P0249 returns. If it does not, the connections were probably your problem.
If the code returns, we will need to test the solenoid and its associated circuits. Typically, there are 2 wires to the wastegate/boost control solenoid. First, disconnect the wiring harness going to the wastegate/boost control solenoid. With a digital volt ohm meter (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 should not be open or shorted. Check the resistance specifications for your particular vehicle. If the solenoid is open or shorted (infinite resistance or no resistance / 0 ohms), replace the solenoid.
If this test passes, with a DVOM, ensure you have 12V at the power supply circuit of the wastegate/boost control solenoid (red lead to the solenoid power circuit, black lead to a good ground). Make sure the ignition is on. If there is no 12 volts at the solenoid, or if there is 12 volts when the ignition is off, repair the wiring from the PCM or relay to the solenoid, or possibly a faulty PCM.
If that is okay, check that the wastegate/boost control solenoid is being grounded properly. Connect a test light to the 12V battery positive (red terminal) and touch the other end of the test light to the ground circuit going to the ground of the wastegate/boost control solenoid circuit. Using the scan tool to actuate the wastegate/boost control solenoid, check if the test light illuminates each time the scan tool actuates the solenoid. If the test light does not illuminate, it would indicate the circuit problem. If it does illuminate, wiggle the wiring harness going to the solenoid to see if the test light flickers, indicating an intermittent connection.
If all tests have passed so far and you continue to get a P0249 code, it would most likely indicate a failing wastegate/boost control solenoid, although a faulty PCM cannot be ruled out until the solenoid has been replaced. If in doubt, seek assistance from a qualified automotive diagnostician. PCMs need to be programmed or calibrated to the vehicle in order to be installed correctly.