Engine Light ON (or Service Engine Soon Warning Light),Possible higher fuel consumption,Possible more smoke from exhaust than usual
P0155 MERCEDES-BENZ Possible Causes
Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1,Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit fuse,Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted to ground,Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection,Faulty Engine Control Module (ECM)
P0155 MERCEDES-BENZ Description
Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature the faster the sensor will start sending an accurate signal to the Engine Control Module (ECM). In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground. This fault code is stored in the engine control module when the current flow through the oxygen sensor heater circuit is not as expected. The ECM uses a comparator to measure the voltage drop across a known resistor, using this value the system can calculate the current flow within the circuit. The supply voltage to the component must be investigated. The resistance of the heater element should also be tested. A resistance of approximately 8 Ohms to 15 Ohms is satisfactory. Due to the location of this component the electrical connector can become contaminated with splash from the road. Separate the electrical connector and inspect the pins for corrosion.
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