There are two catalytic converters worth doing a quick test, and I’ll show you some interesting values.
Many adapters are applied to connect Mercedes to PC to run original software Xentry: Super MB Pro M6, VXDIAG VCX SE, SD C4 Plus…
1.Check if catalyst is working
Go to engine control unit.
Don’t forget to check “I confirm that I have read the safety information”.
Start the car and switch to “Actual values”.
Unfold “Check combustion engine while idling”, we would find two values – Lambda control upstream/downstream of catalytic converter, that is the upper/lower sensor.
To see how the upper sensor work, select it and click on “Continue”.
Select these two options and display the bar graph.
As the values fluctuate around the acceptable range, everything is normal, and the left and right block of cylinders is going on.
2.Check catalyst efficiency
Then select another option – downstream, which is for checking the efficiency of the catalyst, instead of if they are working like before.
Enter its menu and check the left and right sensors to display its line graph.
The catalyst here is much lower and higher. We cannot know what happens only by these graphs.
3.Check oxygen supply in catalyst
So now we’re about to do a catalyst test.
Go to tests and scroll down to check oxygen supply in the catalyst.
Idle the engine and switch off all consumers as required and continue.
Now we see the temperatures should be slightly adjusted by gas pedal.
So we press the gas pedal until everything is green.
Continue to the next step – Exhaust volume that flows through the catalysts.
Start of evaluation ACTIVATED.
The result is not comprehensive, but it’s a measurement of oxygen in the catalyst converter.
The oxygen supply in the left is much less than in the right, but from the graph before, we see the left part is overestimated.
Then back to Test menu and right/left oxygen sensor upstream tests are available.
As a consequence, with the left catalytic converter, something is wrong or missing, we need to check it with a scope.
Finally, the numbers are not clear. What unit and some coefficient are possible.You have to look at a lot of machines and compare like the brake pedal written on the floor and the gas in the catalysts.
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