O2-Sondenheizung Function
O2-Sondenheizung Function
Shown on Engine 119
B11/4 Coolant temperature sensor
F1 Fuse and relay module Model 163
G3/1 O2 sensor downstream of TWC Engine 111, 104 (USA) and EURO3/4
G3/2 O2 sensor upstream of TWC Engine 111, 104
G3/3 Left O2 sensor upstream of TWC Engine 112, 113, 119, 120
G3/4 Right O2 sensor upstream of TWC Engine 112, 113, 119, 120
G3/5 Left O2 sensor downstream of TWC Engine 112, 113, 119, 120 (USA) and EURO3/4
G3/6 Right O2 sensor downstream of TWC Engine 112, 113, 119, 120 (USA) and EURO3/4
K1/2 Overvoltage protection relay Model 124, 202 up to 7/96
K40 Relay module model 170, 210 up to 2/97
K40/4 Fuse and relay module Model 202 as of 8/96, 210 as of 3/97
K40/7 Right fuse and relay module Model 215, 220 (K40/4 in Model 230)
L5 Crankshaft position sensor
N3/4 HFM-SFI [HFM] control unit
N3/10 ME-SFI control unit
N10/1 Front SAM control unit with fuse and relay module Model 203
N16/1 Base module, model 129, 140
The engine shown is engine 166
B11/4 Coolant temperature sensor
G3/1 O2 sensor downstream of TWC (low emission EURO3/D4)
G3/2 O2 sensor upstream of TWC
K1/6 Electronics relay
L5 Crankshaft position sensor
N3/5 ECM control unit (up to 08/01)
N3/18 ECM control unit with throttle valve actuator (as of 09/01)
The purpose of the O2 sensor heater is to rapidly heat up the O2 sensors to their operating temperature while preventing damage to the sensor ceramic as a result of controlled heating power.
The sensor heater is actuated by the engine control unit through ground. The performance of the sensor heater at operating temperature amounts to:
18 w on Engine 104, 111, 119, 120 and 112, 113 with ME2.0
12 w on Engine 166 .
7 W on Engine 137, engine 111EVO and 112, 113 with ME 2.8 as of 06/00
The voltage for the sensor heater is supplied by the:
- Overvoltage protection relay model 124, 202 up to 7/96
- Relay module, Model 170, Model 210 up to 2/97
- Base module, Model 129, 140
- Fuse and relay module, model 202 as of 8/96, model 210 as of 3/97, model 163 designation F1
- Electronics relay, Model 166
- Right fuse and relay module (K40/7), Model 215, 220
- Right fuse and relay module (K40/4), Model 230
- Front SAM control unit with fuse and relay module Model 203, 209, 211
The current in the cold state is increased by approximately 4 times. At coolant temperatures below approx. 20 �C and at high engine speeds, the sensor heater is switched off.
Engine 112, 113
The sensor heaters for the left and right O2 sensors are connected in parallel in the ME-SFI control unit.
Engine 119
The sensor heaters for the left and right O2 sensors are connected in parallel.
Engine 120
The sensor heaters for the left and right O2 sensors are assigned to the respective engine control unit.
Engine 137
Each sensor heater has its own, short-circuit proof output stage in the engine control unit with diagnosis. As a protection for the ceramic, the sensor temperature upstream of TWC is limited to approx. 350 °C in the condensation phase after cold start. After this, the temperature is controlled to approx. 700 °C. An exhaust temperature is determined from various engine operating data for this purpose and the sensor heated accordingly.
Different values apply to the O2 sensor heaters downstream of TWC.