Mercedes Benz CLK 209 2002 - Engine CAN BUS help please, code C1024 - Fixed #
Posted by Martin Kelly on August 2, 2012, 7:32 pm
Year of Manufacture *: 2002 Engine Size and Code *: 2.0L 271.940 ( Optional ) ECU Type: Siemens 5WK90449 ( Optional ) Scanner Used: Verus, Picoscope ( Optional) Fault Codes: ESP - C1024 CAN communication with engine faulty
Hi,this fault has occurred intermittently over the last year, putting the car into limp mode, and now is very much more frequent, almost constant. I pinned into the hi speed CAN BUS junction in the drivers footwell area and captured the trace shown below.
I then disconnected each control unit from the junction connector in turn until the trace returned to a correct CAN BUS waveform. This was when the engine ecu was disconnected. I then pinned into the engine ECU multiplug CAN pins and with the ECU multiplug disconnected from ECU the trace was good, on re-connecting to ECU it went bad as above. This confirmed the wiring from the junction connector to the engine ECU was good and the fault is within the engine ECU itself. Is my procedure here ok or have I missed something? I then decided to get the ECU tested, difficult to test these apparently but used a company on the Isle of Wight (as recommended by Allcar Electronics) as they have done these in the past. Result; nothing wrong with it. Phoned local Mercedes parts to find that these ECU's have been superceded 8 times and 42 have been sold in the UK in the last 12 months.
I am now at the stage where I am sure it's the ECU faulty but would like confirmation that my diagnostic procedure is correct.
Hi, I thought I would bring this saga up to date as I get a bit dissappointed when people don't always post their fix.
I will try to shorten this as best I can but this has only recently been resolved.
The customer wanted me to deal with the vehicle and I kept him informed as work proceeded.
After my initial posting the car was booked in at the local Mercedes dealer for the following week to confirm the ECU fault and replace if necessary as they were the only one's that I knew could program it. By the time the car went there it would not crank over. They had it for 3 months and replaced the EIS,electronic ignition switch. All ran ok for about 50 miles then warning messages appeared in dash - brake pad wear, coolant level, battery warning light.
It has a smart alternator and the info on Merc WIS says connect Star and follow procedure, so I could not get any useful info on alternator to check it. It was charging max 25A at 13v.
I decided I had reached the point where I had to pass it onto someone with proper Mercedes experience and so it went to a Merc independant. I informed them of previous history.
They diagnosed SAM,signal aquisition module, faulty, replaced it and alternator and all other dash faults returned to normal.
After they called me to say it was done, the car refused to crank over.......not again!
After some investigation they concluded it was CAN fault and their hunch was engine ECU. They sent it for testing at their tester of choice and it came back "no fault found".
After extensive engine wiring loom inspection it was found that moving one of the ECU multiplugs about 1mm to one side the car started. The multiplug was dismantled to check pins - all ok.
We agreed, with the customers ok, to replace the engine ECU.
The car has been fine since then.
____________
Was the original EIS ok and did the engine ECU coincidentally come back to life?
This probably highlights the fact that there is no better test bench than the vehicle itself.
It also shows that the Merc. independant and I were both looking at the same end result but we got there by different means, he with his Star machine and me with my trusty scope.
If only we'd changed the ECU last August!!!!!!
Apologies for long post, Martin.
Re: Fixed #
Posted by Malcolm Probert on March 16, 2013, 5:52 pm, in reply to "Fixed #" Malcolm Probert
I don't see the need for any apology. The tale just shows how fraught the process of choosing, and relying, on ECU testing establishments to be faultless, is. Their false declarations, without qualification, seem to lead to much (unnecessary) work, and worry.
on March 16, 2013, 5:52 pm, in reply to "