Sickly A-Class - any help appreciated

[jeley]

Hi,

I wonder if anyone here can help point me in the right direction with a rather sickly 2003 A160 Auto. The issues:

Engine Management Light on
BAS/ESP Light on
No gearbox indicator display in dash
In Limp Mode (won't go over 30mph)
Gearbox in limp mode (Reverse and 2nd gear only and engages with a clunk)

Note that the gearbox indicator is not saying "F" - it is entirely blank. I've plug a diagnostic scanner in and it will not comminucate with either the engine management or gearbox modules. The only systems which will talk are the traction control which has a C1024 Code ("CAN Bus fault in communication EGS/ESP") and the gearbox selector module which has a P1875 Code ("CAN Communication").

Basically, the entire engine ECU and gearbox ECU seem to be absent.

This obviously points to a ECU failure somwhere but which one, engine or gearbox?

Any pointers greatefully appreciated.

 

[DSM10000]

Get it to a dealer or specialist with STAR and get the car properly scanned otherwise you are just guessing.

OBD scanners give (as you have found out)very limited diagnostics and generally do not communiucate with ECU's.

 

[jeley]

It wasn't with a generic OBD scanner, it was with the latest Solus Pro system which isn't STAR but should still talk to it. That said, I did try a generic OBD II scanner, and that didn't talk either.

As far as I can make out the CAN Bus system seems not to be talking to anything.

 

[BlackC55]

Check the basics first like fuses etc

 

[jaymanek]

If not fuses its going to be the common component, i.e. instrument cluster or like you say the control unit... we have changed a few of both now.

 

[jeley]

Thanks for the replies.

I can't see anything obvious as regards the fuses.

I guess I am going to have to bite the bullet and get the local Mercedes dealer to do a diagnosis (I won't get the to do the actual work).

It seems failure of both the main ECU and gearbox ECU is quite common - fortunately there seem to be numerous ways of repairing them so that will be the route I go as the car just isn't worth spending serious money on.

When you say control unit do you mean the gearbox one or the main ECU?

 

[jaymanek]

Cant guess really, best to go to dealer as they can throw parts at it and put them back if they dont work...

 

[Auto-mobile]

Stands a chance on being gearbox electrics pack/valve chest/Ecu circa 1k

 

[nick mercedes]

I guess I am going to have to bite the bullet and get the local Mercedes dealer to do a diagnosis (I won't get the to do the actual work).

A good indi should be able to diagnose the problem for a fraction of what MB will charge.

 

[paris2463]

Stands a chance on being gearbox electrics pack/valve chest/Ecu circa 1k

nicks right prob gearbox but check on star system indis have star

 

[jeley]

Does anyone know of a decent Mercedes indi in North Essex?

Obviously I can't take the car too far as it will only do 30mph!

 

[zaurimak]

it is

for me the same problem, the same car , can any help

 

[jeley]

Well, I put into Mercedes for a diagnosis.

£70+VAT later I get 23 seperate fault codes relating to gearbox, Engine and various other modules.

Their verdict is that the gearbox control unit is dead - virtually all the codes relate to CAN faults so it seems to have "fallen out the loop" so no control modules are talking to any other control modules.

So, basically, what I suspected was wrong is it but at least I know now.

I'm going to get the gearbox ECU removed and sent off for testing and/or repair and try it. Of course, I do now know whether the gearbox is mechanically OK or not but there are no codes stored relating to any physical gearbox issues - they are all electrical CAN bus.

It simply isn't worth spending £1000+ on a new unit as the car doesn't justify it.

 

[jeley]

Just to bring this to conclusion, the ECU was removed and sent to ECU Testing for repair.

After about a week they declared it a "processor fault" and they couldn't repair it and are sending it back to me today.

Sadly, that means it is curtains for the car. It seems a bit sad to scrap a 2004 car with 70k on the clock but the figures do not add up to repair it. When it was on the ramp having the ECU removed from the gearbox it was also pretty shocking to see the amount of general rust on the subframes, wheelarches etc.

This car clearly wasn't Mercedes finest moment.

 

[forrera]

your transmition ecu is burnt out beyond repair

 

[dulayj]

yep its unfortunate-repairs become uneconomic

 

[forrera]

most of the time star diagnose is able to reset the system and make F show on display, then clear faults and it's back to life again.
however, it's only matter of time untill it worms up and the same problem will certainly happen again.