DTC Code P0279 – What does this code mean for Mercedes?

<ul> <li><b>Engine Light ON (or Service Engine Soon Warning Light)</b>: The engine control module (ECM) detects an issue with the cylinder 7 injector circuit, triggering the warning light. <causes> could include a faulty injector, wiring issues, or a malfunctioning ECM.</li> <li><b>Engine Misfire</b>: A misfire in cylinder 7 can occur due to insufficient fuel delivery. <causes> may involve a defective injector, poor electrical connections, or a damaged injector driver in the ECM.</li> <li><b>Engine Run Rough</b>: The engine may run rough due to improper fuel injection in cylinder 7. <causes> could be a clogged injector, broken wiring, or a failing ECM.</li> <li><b>Low MPG</b>: Fuel efficiency may decrease as the engine compensates for the injector issue. <causes> include a malfunctioning injector, electrical problems, or ECM faults.</li> </ul>

<ul><li>Dirty fuel injector 7 can restrict fuel flow, causing improper combustion.</li><li>Faulty fuel injector 7 may fail to deliver the correct amount of fuel.</li><li>Plugged fuel injector 7 can block fuel delivery, leading to misfires.</li><li>An open or shorted fuel injector 7 harness can disrupt the electrical signal needed for proper injector operation.</li><li>Poor electrical connection in the fuel injector 7 circuit can result in intermittent or no injector function.</li></ul>

<ul> <li><b>Initial Scan</b>: Use an OBD-II scanner to confirm the presence of DTC P0279 and check for any additional codes.</li> <li><b>Visual Inspection</b>: Inspect the wiring and connectors for Cylinder 7 injector for any signs of damage, corrosion, or disconnection.</li> <li><b>Injector Flush</b>: Perform an injector flush to clean any potential clogs in the fuel injector for Cylinder 7.</li> <li><b>Check Injector Resistance</b>: Use a multimeter to measure the resistance of the Cylinder 7 injector. Compare the reading to the manufacturer's specifications.</li> <li><b>Power and Ground Check</b>: Verify that the injector is receiving proper power and ground signals using a test light or multimeter.</li> <li><b>ECU Check</b>: Inspect the Engine Control Unit (ECU) for any signs of damage or malfunction that could affect the injector circuit.</li> <li><b>Injector Replacement</b>: If all previous steps are completed and the issue persists, replace the Cylinder 7 injector.</li> <li><b>Final Test</b>: Clear the DTC code and perform a road test to ensure the issue is resolved and the code does not reappear.</li></ul>

<p>The DTC code P0279 indicates a Cylinder 7 Injector Circuit Low issue in Mercedes vehicles. This is a <b>critical</b> problem that can lead to severe engine performance issues, including misfires and potential engine damage.</p><ul><li>Immediate action is required to inspect and repair the injector circuit.</li><li>Delaying repair can result in further engine damage and increased repair costs.</li></ul>