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O2-sensor heating - fault code description ME - AD07.61-P-4000-08AB

    O2 sensor heater (G3/3 to G3/6), voltage supply
1A Fault code P20BE Right O2 sensor upstream of TWC (G3/4) (P0135)
(USA ONLY Readout on generic scan tool) P20BF Left O2 sensor upstream of TWC (G3/3) (P0135)
P20C2 Right O2 sensor downstream of TWC (G3/6) (P0141)
P20C3 Left O2 sensor downstream of TWC (G3/5) (P0141)
1B Engines 112, 113 as of 1/01
Fault code		 P20BE-[1] Right O2 sensor upstream of TWC (G3/4), short circuit to positive/sensor heater resistance too low (P0135)
(USA ONLY Readout on generic scan tool) P20BE-[2] Right O2 sensor upstream of TWC (G3/4), short circuit to ground (P0135)
P20BE-[4] Right O2 sensor upstream of TWC (G3/4), line discontinuity for sensor heater (P0135)
P20BF-[1 ] Left O2 sensor upstream of TWC (G3/3), short circuit to positive/sensor heater resistance too low (P0135)
P20BF-[2] Left O2 sensor upstream of TWC (G3/3), short circuit to ground (P0135)
P20BF-[4] Left O2 sensor upstream of TWC (G3/3), line discontinuity for sensor heater (P0135)
P20C2-[1] Right O2 sensor downstream of TWC (G3/6), short circuit to positive/sensor heater resistance too low (P0141)
P20C2-[2] Right O2 sensor downstream of TWC (G3/6), short circuit to ground (P0141)
P20C2-[4] Right O2 sensor downstream of TWC (G3/6), line discontinuity for sensor heater (P0141)
P20C3-[1] Right O2 sensor downstream of TWC (G3/5), short circuit to positive/sensor heater resistance too low (P0141)
P20C3-[2] Right O2 sensor downstream of TWC (G3/5), short circuit to ground (P0141)
P20C3-[4] Right O2 sensor downstream of TWC (G3/5), line discontinuity for sensor heater (P0141)
2 Fault storage after expiry of test duration and fault
Actuation of the engine diagnosis indicator lamp (EURO3/4)
or CHECK ENGINE (MIL) malfunction indicator lamp USA ONLY		 following two successive driving cycles with faults
3 Checking frequency Continuous
4 Checked signal or status Checking the current/voltage for the O2 sensor heater
5 Fault setting conditions  Voltage lower than 2.5 volts
Limit values Current higher than 4.2 amps
  Short circuit to ground No voltage on the O2 sensor heater
Short circuit to positive
Open circuit in wiring
6 Check prerequisites Battery voltage between 8 and 17V
7 IMPORTANT Actuation of every O2 sensor heater is tested for line discontinuity and short circuit (to ground or battery voltage). A short circuit to ground and a line discontinuity will be recognized when the output stages are locked, while a short circuit to the battery voltage is recognized when the output stages are conducting. The output stage is immediately no longer activated when a fault arises.
In cases of a fault on the O2 sensor heater check:
  1. Connector, line and fuse.
  2. For a short circuit to ground: measure the resistor between the O2 sensor housing and the sensor heater (connection 1 or 2). Replace the O2 sensor if the resistance is less than 100 Ω.
  3. For a short circuit to battery voltage: check the cold resistance (+25°C) of the sensor heater between connection 1 and 2. Replace the O2 sensor if the resistance is less than 4.5 Ω.
  4. For line discontinuity: check the cold resistance (+25°C) of the sensor heater between connection 1 and 2. Replace the O2 sensor if the resistance is greater than 12 Ω.

View of electrical connection for O 2  sensor 

Fig 1: Identifying View Of Electrical Connection For O2 Sensor
G04606018Courtesy of MERCEDES-BENZ USA
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