Cause of ECU failure in CLK500 (W209)?

[Fivehunnit]

So, I've had a CLK500 (W209) for about 3 months, all was fine until about 4 weeks ago, I went for an overtake, no problem, then afterwards, when setting off from traffic lights and junctions, throttle response was non existent for a few seconds, then suddenly it would shoot forwards, it's also had a sort of irregular idle since a few weeks after I got it, but this got worse after I went WOT for the overtake. Switching off and back on again sorted it, no problems again (apart from the idle, which was sometimes ok, other times a bit shaky) until 2-3 weeks later, again upon WOT, this time, cough cough, all kinds of lights and noises from the dash board, "ESP faulty, visit workshop!", engine check light came on, no throttle response at all, car came to a stop and engine died. This time, upon turning the engine back on, the engine check light stayed on, throttle response was delayed by a split second every time without fail, sometimes it carried on right through until 3,000 rpm or so, other times it was just the split second cough and that's it, sometimes, coming to a stop at lights etc the car would shake, sometimes even shut off.
I had it plugged in at a local garage, which gave codes for "pedal value sensor (short circuit, path 1)" and "MAF sensor".
Having already changed the MAF sensor with a Bosch unit when the problem first happened, I thought it odd, I ordered a new pedal assembly from Mercedes (no part dealers stocked them), put that on, transpires there was no change at all, back to the drawing board.
A few days later, it's in an indy garage who plug it in and get the MAF code but no mention of the pedal sensor, they test the MAF, Potentiometer, throttle body, all found to be fine, they replace any possible wiring that may have been broken inside, no change, they say that the only possibility now, is that the ECU is defective and needs to be sent away to find out if it's fixable, or if I will need a new one, to the tune of £1,400 and 5 working days of delivery time, plus the labour for the diagnostics and work.
My question is, why would the ECU malfunction like that? Is it well known in the M113? I've struggled to find any post where someone had this problem with the W209, lots of older ones and other models caused by oil leaks up wires or ?HT leads shorting? if I get it fixed, or get a new one, is it likely that something caused it and will be ticking away ready to blow it again?
Thanks

 

[S-class]

I had a similar occurance with another car (non merc), indy diagnosed ECU, I took it in to dealer and they diagnosed another sensor which was much cheaper to fix, have you already tried a dealer?

 

[Fivehunnit]

I had a similar occurance with another car (non merc), indy diagnosed ECU, I took it in to dealer and they diagnosed another sensor which was much cheaper to fix, have you already tried a dealer?

No, just an Indy garage with really good things said about them everywhere I've seen (Motor Aid, Basildon) they've had it plugged into the upgraded version of STAR (forgot what they said it was called) which said short circuits for the sensor, but they've been replaced by me recently and tested by them, they said the MAF code is permanent and the sensor is fine, also throttle body and potentiometer is fine and the wires are now stripped and replaced, leaving only the thing between the two (ECU) to be at fault.

 

[Fivehunnit]

I'm sure that when it's sent off to the ECU specialist, they will inspect/test it, if all is well, send it back to the garage saying that it's fine.

 

[Fivehunnit]

Update, the garage rang today saying the ECU is back and the place they sent it were unable to get a proper diagnosis on it or something, the car has to be sent to mercedes themselves and a donor ECU put in to test, can see this being a very long and very expensive ordeal.

 

[Bobby Dazzler]

Before spending any more money I would try a third MAF (ideally from MB rather than Bosch or other), just in case the second is faulty. If you ask you local MB parts counter then they may let you try one if it's already in stock.

 

[AMGeed]

Before spending any more money I would try a third MAF (ideally from MB rather than Bosch or other), just in case the second is faulty. If you ask you local MB parts counter then they may let you try one if it's already in stock.

+1.
Also, if the car is drivable, albeit with a fault, I'd get a 2nd opinion before agreeing an ECU change at the dealer.
Can you get to Wayne Gates at Harrow?
Services - Specializing in Mercedes Benz

 

[Fivehunnit]

Ok, update time.
Well.. You was right! Got a call from the garage today It's sorted, turns out that it was the MAF sensor after all, they put a new MAF in to test it ages ago and it was the same, they tried a different MAF today and it worked, so that means, the new MAF I put in and their new one they tried weeks ago were both no good.
Car seems fine, touch wood, drove home perfect, it has none of the symptoms it had before.

 

[Sliqd]

Hi everyone,

I've got a similar problem with my '02 CLk500, except it was a little bit more bizarre. If got tried to start the engine one Friday morning two weeks ago resulting in just clicks when I turned the key. I changed the battery, no luck. Called Click mechanic and paid the initial fee of £55 for a misdiagnosis of a starter motor fault and a quote £490 to fit it. The *******.

I went to a good local parts dealership and got a starter motor, took it to a local Indy and got it changed for £90. Still no luck. The Indy told me to find an electrician as it's likely to be an electrical fault. Recovered the car to. A local auto electrician who then found out that that water had gotten into the ECU. I wasn't sure how. He then showed me leaves and debris had collected and blocked the windshield drain stopping water escaping and flooding the fuse of instead.

Long story short he sent the ECU for a test and it has been returned as unfixable. Mercedes have quoted £1,400 + labour. As I'm already £500 down going around in circle, I was just wondering before I commit if anybody has any experience of replacing one of these from another car and if it is worth it?

There are some cheap ones on EBay I'm reluctant to touch. Please advise. Thanks.