Because the LH module has a default mode for failure of any sensor including the MAF.

You will set a code though.

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Because the LH module has a default mode for failure of any sensor including the MAF.

You will set a code though.

thanks for your reply.

Ok, I will ask a little bit different: when the engine is running and when i disconnect the sensor, there is no change in idle quality. I believe you what you say, I am familiar with so called maps which are kind of reference for engine management.

So one would expect no change in engine runing only if values in maps are equal to vales acquired from sensors in moment when i disconnect the sensor ... which cannot be the case in practice.

P.S.: i am researching where (if anywhere) there's an error in engine management system. Maybe i can locate the culprit for rough idle by some logic?

 

The intake air temp sensor has a minor affect on the fuel mixture, so you won't notice a difference in the idle.

You can disconnect the MAF, and it will change for a second and smooth right out.

Coolant sensor may have more of an affect, but like I said the LH module has a great default map.

The only real way to test the sensors is with a scanner and see what the LH module is reading.

This not only is a test of all the sensors, wiring harness, but fault codes as well.

Anyone with a M119 (or M104) should have one if they do their own work.

I have a Snap On MT2500. Old school but reads live data and can reset self adaptation. (fuel trim) and read / clear codes

 

that's great answer, thanks.

is this snap on mt2500 ok?:

Snap on MT2500 Diagnostic Scanner OBD1 and OBD2 with Keys and GM ABS | eBay

is it a stand-alone thing or do i need a computer and something more? i assume it is stand-alone thing.

 

It is a stand alone scanner.

You need the software cartridge's for Mercedes, I would get both 1999 and 2003 versions.

And you'll need the MB-1 38 pin adaptor cable.

Personality keys 20 & 21

There's one more key you'll need, I'll have to check my kit, I don't recall the number.

That one is mainly GM software you posted.

Right scanner, wrong software.

 

cool. thanks so far. situation is much clearer now.

 

Hmm some on NON MB SITESare saying that a simple battery change to a spec. cell would do the trick, honest posts or battery salesmen?