C200 merc check engine light

working fool

Hi
I have a 2001 c200 petrol whit the cheak engine light on
It's throwing up code p0101 on the code reader " airflow circuit range performance "

Kinda points to airflow meter
But I've read a bad battery , alternator or even a bad earth can cause this .

Has anyone any experience with this problem ?
Thanks

jimgoose

If 'twas I, I'd clear the code(s), clean the sensor and its electrical connections, check the battery/leads/connectors, and see does the DTC return after a few drive-cycles. Is the car running/starting OK?

working fool

Yeah it seems to be running fine
I only have the car so I've no idea is it running rough at all .
I'd imagine it might be a little quicker all the same .

jimgoose

working fool wrote: »

Yeah it seems to be running fine
I only have the car so I've no idea is it running rough at all .
I'd imagine it might be a little quicker all the same .

You mean a little quicker with the dicky airflow sensor?

working fool

jimgoose wrote: »

You mean a little quicker with the dicky airflow sensor?

Yeah that's what I'm thinking
It a compressor model

I have the propper maf sensor cleaner at home
Going to try that first

jimgoose

working fool wrote: »

Yeah that's what I'm thinking
It a compressor model

I have the propper maf sensor cleaner at home
Going to try that first

Well, most of them will start and run without the airflow sensor - the computer will derive an airflow value from engine speed and throttle position - but it depends. If the sensor is offline completely, you'll probably be running a bit rich as the computer errs on the side of caution. This is great for power, not so good for hydrocarbon emissions and the NCT. If the sensor is online but a little haywire, things may be somewhat more screwed up. I'd get it sorted properly.

working fool

Cheers
I'm going to have a look at it this evening or tomorrow

working fool

Update :
I cleared the code and the car was perfect .
I took off the airflow meter and cleaned it
Looked ok
Drive the car for 2 days and the code came back :-(

I'm gonna test the map sensor tomorrow
Don't want to go buying a new airflow before I'm sure that's the problem
They're nearly €300
Ohh and the battery is brand new in the car so that's not the problem .

Irishcrx

Have you checked the simple thing's as well, such as any breaks or tears in the airflow housing? , is the air filter dirty? This can sometimes throw up codes relating to the MAF, have you checked all the leads connecting into the MAF for breaks or damage?

Generally if the MAF itself was the problem the car would be misfiring or driving rough..

working fool

Irishcrx wrote: »

Have you checked the simple thing's as well, such as any breaks or tears in the airflow housing? , is the air filter dirty? This can sometimes throw up codes relating to the MAF, have you checked all the leads connecting into the MAF for breaks or damage?

Generally if the MAF itself was the problem the car would be misfiring or driving rough..

Yeah I had a quick look at it
Everything seems fine
The car runs perfect when I clear the fault code .
The air filter is new too.
It has a plastic inlet manifold
Might check that for cracks this evening

burke027

Personally from experience.
U say it looks ok. ??
They all do as they break par say that u can see so u can't be sure it's ok. U need to be sure it's reading the right air flow.
Secondly these give alot of trouble with the vacuum pipe under the air filter housing collapsing I'd start there they a very prone to vacuum leaks. I've seen plenty down through the years

Irishcrx

working fool wrote: »

Yeah I had a quick look at it
Everything seems fine
The car runs perfect when I clear the fault code .
The air filter is new too.
It has a plastic inlet manifold
Might check that for cracks this evening

Ok, when the fault code is on does it run rough or stutter?, if so disconnect the MAF and take it for a drive if it revs freely then (It might idle off when it's disconnected) then the MAF is your problem if it doesn't make a differance it's something else.

working fool

burke027 wrote: »

Personally from experience.
U say it looks ok. ??
They all do as they break par say that u can see so u can't be sure it's ok. U need to be sure it's reading the right air flow.
Secondly these give alot of trouble with the vacuum pipe under the air filter housing collapsing I'd start there they a very prone to vacuum leaks. I've seen plenty down through the years

Thanks
Mine is the compressor engine
The air filter box is at the front of the rocker cover .
Ill Investigate further .

working fool

Irishcrx wrote: »

Ok, when the fault code is on does it run rough or stutter?, if so disconnect the MAF and take it for a drive if it revs freely then (It might idle off when it's disconnected) then the MAF is your problem if it doesn't make a differance it's something else.

It doesn't seem as powerful when the light is on , but it's very drivable and runs fine .
Ill take it for a run with it disconnected this evening

Thanks again

jimgoose

working fool wrote: »

Thanks
Mine is the compressor engine
The air filter box is at the front of the rocker cover .
Ill Investigate further .

Ah, supercharger. Interesting.

working fool

jimgoose wrote: »

Ah, supercharger. Interesting.

Yeah it's goes like a rocketship

Here's the fault code

working fool

Update

I took the throttle body apart lastnight
There was a small buildup of encrusted oil on the housing and the gauze inside the throttle body .
I cleaned that .
And there's 2 map sensors on the inlet
One going inside the manifold and one just bolted to the plastic manifold doing nothing ??
I swapped them round because they are identical " part no's etc"
Put it back together and cleared the code again .
It might sort out the problem
All the vacuum pipes where ok .

working fool

It's been a week now
And I've driven the car for a few days and no return of the check engine light