Engine Light ON (or Service Engine Soon Warning Light),Excessive Fuel Consumption
P0174 MERCEDES-BENZ Possible Causes
Intake air leaks,Faulty front heated oxygen sensor,Ignition misfiring,Faulty fuel injectors,Exhaust gas leaks,Incorrect fuel pressure,Lack of fuel,Faulty Mass Air Flow (MAF) sensor,Incorrect Positive Crankcase Ventilation (PCV) hose connection
P0174 MERCEDES-BENZ Description
This fault code is stored in the Engine Control Module (ECM) when the ECM is no longer capable of controlling the air fuel ratio. For correct operation of the catalytic converter the ECM is required to keep the air fuel ratio (AFR) at approximately lambda 1, this equates to an AFR of 14.7:1 by mass. This is achieved by trimming the fuel mixture to the required amount to cater for slight anomalies during normal operating conditions. However when a fault causes the fuel trim to exceed a predetermined level the malfunction indication light is illuminated and a limited operating strategy is employed. The pre-catalyst exhaust gas oxygen sensor is the primary component used for calculating the fuel trim once the system enters closed loop control. The fuel trim data can be displayed as a percentage, either positive or negative. Under this condition the fuel trim data will display a positive value. The ECM will increase the injection duration to counteract the excessively lean mixture. This fault can be stored due to an air leak in the induction system, the exhaust system in close proximity to the exhaust gas oxygen sensor, low fuel pressure, faulty fuel injector or a mechanical defect affecting the engine.
Leave a Reply