check engine light

[Chas]

S class W220 2001 S320 petrol 2001, 95k miles

My check engine light is on and car is in limp mode ( reduced power)

It starts ok and revs are stable ( Full MB service history)

Any any ideas? Its petrol so no EGR valve, could it be a dirty blocked intake manifold?
I have disconnected battery and it clears the check engine warning light temporarily, it reappears the next day !

Thanks

 

[Cole@MBS]

Airmass or a pair of leads to start the guessing off, you no we want fault codes Chas.......

 

[Chas]

Thanks, taking car to MB tech this week Will let you know outcome ...

 

[television]

Yes the MAF is a good one to start with, this does not turn the lamp on, it is the O2 sensor when it tries to compensate.

How is life young man

 

[Chas]

Life is good Malcolm, took early retirement two years ago, never looked back

Spend most of my time with wild life photography http://www.wildfeathers.co.uk , and enjoying the free time with my family

Hope all is well with you too Malcolm?

I suspect its the MAF,had a word with MB tech independent, great guy local in Ayr, Jon Thomson ex tech manager at MB dealers, he is picking the car up this week to test drive and then diagnose

Will let you know the outcome

 

[Chas]

Yes the MAF is a good one to start with, this does not turn the lamp on, it is the O2 sensor when it tries to compensate.

How is life young man

Hi Malcolm

Just a quick question if you have time. These things annoy me and I like to sort them myself

I unplugged the MAF and symptoms were exactly the same as before.

Engine starts fine from cold, revs at 1200 for 10 secs or so , then revs drop to 800

Foot on pedal, revving up fine full power, 10 secs later back to reduced power mode

Does this mean

A. The MAF is faulty

B. The MAF is ok and something else is faulty..........0 2 sensor ?

Thanks again Malcolm

Chas

 

[television]

If there is no change with it unplugged, then I think we could say it is faulty.

The MAF sets up the fuelling according to the temp, when the MAF fails the 02 sensor tries to compensate, now the 02 sensor is coded to the engine and works within a set + or - element, if it shifts too far from its stored setting, this turns on the warning lamp, most lamps will turn off on their own after a few hard drives and the original fault corrected.

As always I would hate you to buy something that you did not need, so what do you do. The cheapest place to buy one is from any Bosch service center

 

[Chas]

Thanks Malcolm

I will let the tech guys diagnose the fault. I can get a new Bosch MAF £170 or cheaper one for £50 with 1 year gaurantee

When did you go "CL" What happened to your wonderful SL ?

 

[television]

Thanks Malcolm

I will let the tech guys diagnose the fault. I can get a new Bosch MAF £170 or cheaper one for £50 with 1 year gaurantee

When did you go "CL" What happened to your wonderful SL ?

I am looking after my ex now who has severe memory problems,,, and she found it too hard to get in and out of the SL, so I bought a 140 CL420 and then a 216 CL500 , but with 3 cars I am going to sell the CL420, I just cannot drive them all. The 216 is fully loaded with ever toy that you can have, so that keeps me happy

I am pleased that you are keeping busy too enjoying what you like to do

MB tech always do not like me for telling folk to change the MAF without a test

 

[Argus]

I'd be interested in knowing the outcome of this as a pal of mine had the Check Engine Light come on today. Same model and very similar age and mileage. Doesn't mean it's the same fault of course but a good indication for a start.
I hope yours gets fixed quickly and without too much of the folding stuff from your back pocket

 

[Chas]

Jon Thomson, MB tech Indi, Ayr picked up the car this morning at my home, took car in to diagnose fault. Just got a call, it was the throttle potentiometer fault code. He cleared the fault, started up the car, running perfect !!
He also got the exhaust bracket welded at the unit next door to him.

£ 80 for the lot, that is what I call excellent service.
http://www.automotivesolutionsayr.co.uk

 

[television]

Thanks and nice to know that one

 

[Miffy]

When mine went it displayed a very differnt error. MIL came on and throttle responce was very poor. But it would still get to a decent speed

Sent from my GT-I9300 using Tapatalk 2

 

[Chas]

Update :-(

Started car this morning, check engine light back on, same symptons as before

Will take car back in to investigate....

The findings yesterday were" B37 POTENTIOMETER (THROTTLE PEDAL) stored fault, actuation and actual test within spec,
Cleared fault memory and tested, no fault "

Wish me luck

 

[television]

I will say it is the MAF but then I always say that

 

[Chas]

Watch this space Malcolm

ps

I am told a car will run fine temporarily with MAF disconnected, whether it is ok or faulty. If the MAF is faulty the car wont run ok when plugged in

 

[Chas]

Update

I disconnected the battery for an hour, reconnected, started her up and engine check light not showing, but still reduced throttle power. Switched ignition off, took key out, started her up again and running perfect

Must be one of those annoying electrical things ?

Will keep you updated

 

[television]

MAF

 

[Chas]

 

[television]

Its a switchable fault the MAF but I get teased on this,,,, I have been right though oodles of times