On-Board Diagnosis System II - Volkswagen Technical Site

System Components (Gasoline Engine)
Lamdba probe voltage tester
The lamdba probe voltage tester tests the electrical function of the probe.
The system detects and differentiates between short-circuits to positive and ground, as well as open
circuits (e.g. cable breakage).
Fault detection is dependent on whether the signal is too high or too low.
Lambda probe G39
is the primary catalytic converter probe.
Effects of signal failure
If the lambda probe signal fails, lambda control
does not take place and the lambda adaption
function is disabled.
The tank ventilation system goes to emergency
mode.
The Motronic control unit uses a map-based
open control loop as an emergency function.
Electrical circuit
175_054
G39
175_055
Lambda probe G108
is the secondary catalytic converter probe.
Effects of signal failure
175_056
The engine lambda control remains operational
even if the secondary catalytic converter probe
fails. Only the function of the catalytic converter
can no longer be checked if the probe fails.
In the Motronic M5.9.2, the function test on the
primary catalytic converter probe no longer
takes place.
Electrical circuit
G108
175_055
30