Measurements and analysis with the VAS 5051
Lambda probe G39
The lambda probe is located in the exhaust pipe upstream of the catalytic converter. The engine control unit receives a voltage signal from the lambda probe on the composition of the exhaust gas. The engine control unit controls the injectors such that the quantity of injected fuel results in an air/ fuel ratio of approx. = 1.0.
The adjacent circuit diagram shows the electrical connections on the lambda probe G39 of the 1.8 l/92 kW petrol engine.
The electric signal for subsequent analysis by the DSO is measured at the following contacts:
DSO 1 (+)
DSO 1 ()
Contact 4 (signal) Contact 3 (ground)
Lambda probe adapter VAS 5103
The lambda probe adapter VAS 5103 is used to connect the tester measuring leads to the lambda probe connector. The adapter lead is designed for two different versions of lambda probe connectors.
The unused connector must be disconnected.
The lambda probe heating signal between con- tacts 1 and 2 and the lambda probe signal between contacts 3 and 4 can be displayed as a curve by intermediate connection of the adapter lead which permits parallel connection of the DSO measuring lead of the VAS 5051 tester to the connector for the lambda probe.
The following curve is approximately obtained for the lambda probe signal at idling speed: