Lambda Control

Oxygen-Sensor Control MSS65

Functional description, see BMW Service Technology:
TIS -> Document -> SI Technology -> Enter SBT Number
SBT number:
- 11 04 04 097

Lambda probes
For oxygen-sensor control, the S85 is fitted with 2 control sensors (LSU 4.9) and 2 control sensors (LSH 25).

Plausibility check of the Lambda oxygen sensors before and behind the catalytic converter
In this system test, rich / lean shifts in the air/fuel mixture are used to check whether the Lambda oxygen sensor signals are within certain windows.

Dynamic check of oxygen sensors before catalytic converter
This system test determines by means of lean/rich shifts in the air/fuel mixture the amplitude height of the oxygen sensors before catalytic converter. The diagnosis result is a value from 0 to 1 per bank. The higher the value the better the condition of the sensor.

Target value: diagnosis result > 0.4

If the value is less than 0.4, the vehicle must be driven:
- Engine at operating temperature
- 2 min at approx. 2500 rpm
- Speed > 60 kph
- lower part-load range
- run at least one coasting phase of approx. 3 seconds

Before driving, the engine has to run without interruption for 18 minutes so that the diagnosis can run. The engine must not be switched off before the journey is completed, as otherwise the 18 minute count starts from the beginning.

If no oxygen-sensor fault is stored in the DME after the road test, the oxygen sensors are OK. If a fault is stored, the sensor concerned must be replaced

Catalytic converter diagnosis
The vehicle must be driven for the catalytic converter diagnosis:
- Engine at operating temperature
- 2 min at approx. 2500 rpm
- Speed > 60 kph
- lower part-load range
- run at least one coasting phase of approx. 3 seconds

Before driving, the engine has to run without interruption for 18 minutes so that the diagnosis can run. The engine must not be switched off before the journey is completed, as otherwise the 18 minute count starts from the beginning.

If no fault (catalytic converter conversion) is stored in the DME after the road test, the catalytic converters are OK. If a fault is stored, the engine-proximate catalytic converter concerned must be replaced. Before replacement of a catalytic converter, it must be ensured that the oxygen sensors have no faults!