tecnotest STARGAS Manuel D'utilisation page 44

LAMBDA PROBE TEST ____________________________________________________________________ STARGAS
At this moment the engine must be really warmed up by having the vehicle
running along at least 3 km at a speed allowing the probe, if non-heated, to
reach the right temperature, and above all, with both sorts of probe, to
eliminate possible residues that have made a deposit during the ordinary use;
in some cases it is advisable to keep the engine accelerated for a
few minutes between 2500 to 3000 rpm even during the test .
After carrying out the correct warming up, in the workshop immediately
evaluate the efficiency of the Lambda probe signal by means of the
previously prepared connection and insert the gas sampling probe into the
exhaust pipe of the vehicle in order to check alternatively the exhaust gas
reading too.
If the probe proves to be FAULTY a verification of the wiring must
immediately be carried out by executing a simulation test .
If it immediately proves to be EFFICIENT instead, it is possible to verify if it
keeps in this condition by carrying out other tests.
As a matter of fact if the probe efficiency lowers so as to reach the FAULTY
condition, the causes can be the following ones:
•
Engine having quite high emissions of unburnt hydrocarbons (HC) that
often cannot be found out when discharged due to the catalyser action
and/or the emission of carbon residues.
•
Non-heated Lambda probe that, when the engine is idling, cannot
reach a sufficient work temperature to generate a correct signal for the
central unit.
•
Lambda probe of the heated type not operating in the optimum way;
verify by means of a multimeter if the tension (12 V) is present in
parallel to the heater and if the resistance value is correct (2÷10 Ω cold
values) according to the kind of probe.
NOTA BENE:
The Lambda probe diagnosis is very precise thanks to the use of parameters
that have already been worked out in tests and studies for the German
market on the occasion of the AU approval.
40 OPERATING INSTRUCTIONS