'Coding' Marcedes ECU's

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Sun 23 Jan 2005 16:31
'Coding' Marcedes ECU's - Aprilia
Recently came across an out-of-warranty Mecedes A-class that was lacking power and generally running badly. I took a look at it and advised the owner that the AFM was probably at fault.

As A-class owners may know the AFM is integrated into the ECU and sits on the right hand side of the engine as one unit. An entire new unit would be needed, so I suggested to the owner that she go to the dealer to get them to sort it out.

Anyway, I saw her yesterday and asked how it had gone. Apparently the ECU cost about £600; 'fitting' was a whopping £100, but what astonished me is that they charged her almost £200 to connect the new ECU to their diagnostic computer to 'code' it to the vehicle chassis. Basically the a new ECU won't talk to the exisiting components unless they all have the same chassis code. An astonishing charge for a couple of minutes work.
Reply | Report as offensive | Link
Sun 23 Jan 2005 21:19
'Coding' Marcedes ECU's - Dave N
I think Merc have, or are, moving over to a situation where the computer in the dealership can't actually do much any more. For the bigger jobs like coding ecu's, they have to plug the car in, then the computer has to be linked up to the central mercedes computer, and that does the recoding remotely. It's all part of the deal to cut out independants. Basic OBDII stuff can still be done as that's a legal requirement, but for an independant to be able to do the bigger stuff like coding, they have to buy the computer, buy an 'account' with the main computer, and put in an ASDL line. Of course, the manufacturers claim this is the only way to ensure all repairers only use the latest updates, which is true to an extent.

This applies to pretty much everything on cars now, even disconnecting things like zenon headlamp modules with the battery disconnected, that headlamp won't work again until it's 'spoken' to the factory.

Doesn't justify £200 though, but may go some way to explaining the high costs. Plus, being an A class, they probably had to recode a load of other stuff that used to work, but then didn't after they'd fiddled around with the software trying to get everything to communicate again.

Reply | Report as offensive | Link

From which small car to buy at which price point to the best UK-built cars, our Top 10s have the lot. Click now for your shortlist.

Unsure of what to buy? Our Top 10s are here to help you....