W203 A209 No Crank - No Start - Drives Great

[hofnerpres1]

Here's a good one for the Guru's and hopefully somebody else can learn from my journey. I swopped battling with rusty old classics to risk the electronic minefield of the "Modern Classic". Found a 2006 CLK C200 Komp which had spent it's life in a heated garage - 65K and mint. The EIS and that EZL had just been replaced so that was a bullet dodged. It managed less than a thousand miles before it was doing the intermittent stranded car horror show. Got the new EIS tested - all seemed good again - few trips later - no crank. ECU, Front SAM and EIS went away to be checked out. The rebuild company got Covid - also got baffled - 8 weeks later back together and another few happy trips. By now I had got up to speed with CAN BUS language and had traced the fault to a failure to pull down the starter relay coil leg to earth on the violet and white wire. The fault returned three counties away but by giving the starter a feed we got home. If this was a daily driver and not a retired man's toy I would have happily drove it off a cliff but it's an amusing puzzle which has convinced me that post 1990 classics are old computers and most will suffer the same fate. So guys. here's the challenge :

Permanent fault - car lights up - no fault lights - No Crank

Starter relay is not being activated by the ECU - bias voltage at the coil instead of being earthed. Power showing at the SAM circuits and all fuses good. I found a spare SAM - same car and part number for beer money so did a swap - same result.

EIS is new and has been tested again twice by two different companies. EZL is new (what a cheap nasty motor unit that is ! ) It works.
It's an Auto. Lever Module has been also tested as good and shows good switching and start enable on the scanner (iCarsoft MB)
Transmission Module also scans well - start enable working. Battery is brand new.

When 12v supplied direct to the starter - she jumps into life and drives wonderfully with NO WARNING LIGHTS and everything functioning.

The fun bit. At the CAN B lines at the OBD port we get CAN H zero volts and CAN L at 0.020 volts in all key positions. Does the diagnostic module block this ? The scanner seems also baffled since that is failing to link with anything other than the ECU and the TCM.
At the CAN B junction X30/4 RHS sill well we get happy readings - 11v and 4.5v with everything clean and bright at X30/7 as well.

I'm struggling for a wiring diagram - the downloaded workshop manuals are a very good example of the electronics world - all looks good but often crashes.

Over to you team..

 

[hofnerpres1]

Some progress. Found an online WIS which is legit, in the UK and with excellent support. Dave at downloadworkshopmanuals.com sorted the usual p.i.t.a. download game by swiftly responding to my emails late on a Sunday evening. He separates them by model which keeps the file sizes down but we are still talking needing 2GB free space so you might want to consider using a dedicated stripped out old laptop. The WIS system runs on old Windows 7 coding so you get a copy of VirtualBox which runs on top of your windows 10 PC - a fancy emulator. I now need another week to get up to speed with the system - huge amounts of information for £10 - bargain.

 

[hofnerpres1]

So now we have lots of wiring diagrams and proper diagnosis can begin. I makes sense to look at the lack of CAN feed at the OBD port since a fix here might get us access to some modules. All the CAN circuits are activated at the ignition switch EIS - in key position one all should be awake and showing voltage. The pair here that end up at ODB positions 6 and 14 are the Green and Green/white from positions 3 & 4 at the small 8 way purple plug at the back of the EIS. Access this by dropping the RHS panel under the switch and using the special tool to free the retaining ring around the key slot. Back probing shows they have voltage - it's alive. These two wires first go from the EIS to a connector X18\28 which is shown next to the CAN collector strip X30\7 in the wiring duct LHS door sill area. They then come back to the OBD so we must have a break or bad contact on this line. Now the mystery - after much grovelling around and carpet moulding removal including the Transmission Control Module area under the passengers feet area, we find every other connector except these two. I'll post a separate thread and see if anyone has hit this snafu before the rest of the dashboard ends up covering the garage floor...

 

[hofnerpres1]

Next chapter. X18\28 connector was found on the opposite door sill channel after helpful hints from forum members. The helpful connector location pictures in WIS are LHDrive only and certain wiring will be moved across with the steering wheel and main switches. If you need to check it out it is this oversized beauty :



The smaller male end goes to the EIS and has it's own dedicated output. Testing confirms no voltage here and a transient high resistance so it looks like a dedicated diagnostic control circuit. Suspicion now falls on this or the new iCarsoft MB scanner which is new and has the latest software download. I will try it on friends a Mercedes and take up the saga from there. To Be Continued......

 

[hofnerpres1]

Hot Press - Found a comment in another place that the iCarsoft MB scanner needs the engine running to connect to all the modules. An interesting challenge when dealing with a no start car.... However, gave the starter some juice and success - scanned all 29 potential car killing circuits. Lots of nonsense codes ( which I recorded ) but to be expected after all the swopping, unplugging and testing. Cleared it all off and let her run. Nothing returned - ECU and all modules good. So the start authorisation to crank system appears to remain the problem. The key is recognised and all is powered up at key position 2. This car seems to want a stop/start button which would be easy to fix but that would be defeatist. ECU, TCM and Gear Lever module are all showing start enable. Engine coolant temperature sender is new. No brake lever switch - works on a pressure sensor so we'll start looking deeper at this. Don't miss next weeks exciting and baffling revelations.....

 

[AnthonyUK]

I think it was a diagnosedan video where he bypassed the start relay with a jumper cable to start a car.

 

[hofnerpres1]

Thanks Anthony - I'm thinking of changing my name to Dan - they are both lunchtime viewing for me. I have a jump wire in the glove compartment but stopping for petrol gets some strange looks as you dive under the bonnet and off she goes. It's pointing towards an ECM fault at the moment - no doubt a failed switching MosFet, solder crack, old age etc. It's one of those Siemens black glued on tin lid jobs that Ecutesting wisely don't repair any more. I may take a tin opener to it and just buy a second hand replacement EIS ECM and Key set. We have 5 volt refs and powers at all the sensors I can think of. It would be great to have a definitive list of all the sensors and switches that the start up routine requires. Would make a good sticky. A simple "Bypass the cheap electronic nanny s!!t " start button is looking very tempting whilst we source some spares. Safety would still be good since the car would need to be in Park - controlled by a simple Bowden cable and a mechanical latch in the EIS - a device invented in 1896 by Sir Frank Bowden who founded Raleigh bicycles. I expect it will outlast me and the car... As an amusing aside - In the £1200 invoice which the previous owner had just suffered for the new EIS/EZL there is plainly noted " New interlock cable fitted since the original was broken on removal " Not a Mercedes specialist since we all know it comes out the counter intuitive front way - don't we ?

 

[hofnerpres1]

Ok - Looks we have reached a conclusion. The iCarsoft MB scanner tells me that the brake pressure sensor is reading a healthy 1 to 50 bar - it needs this to tell the EPS/ABS that the driver has got their foot on the brake and starting can go ahead. The ECM/ECU should activate a logic circuit which ends up in a high power transister pulling down to ground the Violet and white wire at plug point No 23 on the front block connector marked "F" on the ECU top. ( If you remove this plug the contact points are clearly numbered ). Continuity testing this wire to the relay in the front SAM showed that there is no wiring harness problem. I did wonder if the SAM intercepted it and added some more control madness but it does not - there is a simple direct connection from the ECU to the starter relay. So with everything tested and found good it looks firmly like another ECM has bitten the dust. I will put out a thread to see who can handle repairs on these sealed can Siemens types. A least I'm not adding to the petrol shortages . To Be Continued ...

 

[hofnerpres1]

Been off the road for 5 months now with just a few trips in between in order that the car can demonstrate the full evil consequence of that joy of the modern world " Intermittent Electronic System Fault". Last an ECM/EIS/EZL bundle came up on flea bay - same model and year CLK A209 2006 Auto . This was a cheap way of confirming my conclusion that the ECM was faulty which everybody told me was very unlikely. It also meant a spare kit for the next nightmare. This is the slim Siemens sealed for life glued on tin cover type SIM LKE which nobody wants to repair. Two suppliers assured me that it was plug and and play. It nearly was and she started and ran - job done ? - NO - SRS unit is vin coded. Seems like this was introduced around the mid 2000s across the range since the module can store crash data. I'm posting this to suggest that if you have to buy a replacement bundle of tricks make sure they include the SRS unit. It's a metal box hidden under the heater controls. There are lots of companies that offer to re-code your SRS and remove the crash data ( legal ?) - changing the vin data is another game and is a Developer Level DAS - Grand Wizards only. Your main dealer will happily sell you a blank new part and accept just one kidney - after programming and VAT you may get change from a £1000. Nice coffee though. I love my old Honda a little more every day.....

 

[hofnerpres1]

So Update. I have good news and BAD news. Last week an ECM/EIS/EZL bundle came up on flea bay - same model and year CLK A209 2006 Auto . This was a cheap way of confirming my conclusion that the ECM was faulty which everybody told me was very unlikely. It also meant a spare kit ready for the next nightmare. This is the slim Siemens sealed for life glued on tin cover type SIM LKE which nobody wants to repair. ( Note the deafening silence on my information request post ). Two second hand parts suppliers assured me that it was plug and and play. It nearly was and she started and ran - job done ? - NO - SRS unit is vin coded. So if you have to buy a replacement bundle of tricks make sure they include the SRS unit. It's a metal box hidden under the heater controls. There are lots of companies that offer to re-code your SRS and remove the crash data ( legal ?) - changing the vin data is another game and is a Developer Level DAS - Grand Wizards only. Your main dealer will happily sell you a blank new part and accept just one kidney - after programming and VAT you may get change from a £1000. Shameless. Nice coffee though. So the search goes back to a rebuilder for the Siemens ECM which at least we now know is the villain of the piece. I have elevated myself to ScannerDan Level Two. More fun no doubt to follow...

 

[AnthonyUK]

Great work and very impressed at your determination.

 

[hofnerpres1]

Thanks Anthony. When you are born as lucky as me you need lots of determination. It is a bit sad that despite searching all the forums and looking at all the spare SRS units for sale the fact that later units are VIN coded seems to be ignored. Perhaps that's why ebay wants £20 and a new part is £700 plus. They are just fancy paperweights with added disappointment... Back speaking to my trusted ECU repairer as to why they don't do these Siemens ECMs. We need to know since they do fail - my fear is they are a multi layer circuit board which are more easily damaged when heat has to be applied. Main dealers say they see very few failures ignoring the fact that anybody with an older car never goes near them. Stay tuned....

 

[Uncle Benz]

If you have developer mode you can find the bit in the EZS where it does the Vin check with the SRS. You need a little bit of technical German, but it’s as simple as changing Ja to Nein

 

[Uncle Benz]

W211 airbag module

I saved a very nice lady a heap of dough today with an MoT test failure for an illuminated SRS light. The airbag module had failed. No comms. She had already had it diagnosed elsewhere, and had bought a secondhand module from eBay. As any fule kno, these units are coded with the chassis number...

forums.mercedesclub.org.uk

When I get a minute I’ll update this thread with some screenshots of the appropriate section

 

[hofnerpres1]

Excellent - Thanks Uncle Benz. ECUtesting came straight back to me to say that the unit is probably no less difficult than all the others but they have yet to build a testing rig for these types - probably due to a lack of demand which is encouraging. I've decided to play safe and send it back home to Germany. ECU.de advertise that they can do these units and they look a serious outfit. The spare set will be saved along with the spare front SAM and live in the boot for long journeys. It's the modern equivalent of my Dad's emergency box in the back of the old Riley RMF which had fan belts, spare points and an SU petrol pump. It's a perfect summer car when the electronics give it a chance

 

[hofnerpres1]

Epilogue...

A well respected local Auto Elec said he was confident he could clone the known good spare ECU by wiping it's files and overwriting with the Vin coded files from the suspect oil soaked original. All went well without resorting to chip changes etc. Sadly, the anti-theft DAS fault has transferred with the files so we now have proof that the fault must lie with some corrupted or missing sections in the ECU software files since everything worked with the the spare unit's old files. Terminal 50 is showing no power which is the CAN signal to the ECU not being activated. I suspect the oil ingress may have scrambled some ones and zero's. A new level of madness. Unless we can get the unit reloaded with the exactly correct files and VIN coded the car will be fitted with an engine start button and we can motor on again ( with the bonus of a spare ECU in the boot). Yes, I know a dealership could probably do it but I doubt they would want to get involved with second hand units and would want to fit a new ECU. Goodbye many hundreds of pounds.

 

[LostKiwi]

If you get another set of modules and @Uncle Benz finds his screenshots I have Developer mode on my Star and am periodically up your way (MrsLK likes it up there). I'd be happy to pop in and code it if you aren't in a massive rush.

 

[hofnerpres1]

Well that's really kind LostKiwi. I've ignored the nonsense over Christmas but have good news. Following on from the attempt at cloning, my crestfallen electronic wizard could only surmise that there is fault in the ECU files which has carried over to the replacement spare. However, the next day I disconnected the battery for an hour to do some unrelated work and guess what - the system had reset itself and the fault has gone ! Starts on the button for the last dozen runs so fingers crossed - we have a resolution. I've got the covers off the ECU top multi plugs so I can keep checking for residual oil migration from the engine harness ( Yes, we have fitted the blocking plugs ). Oil was evident in the Alternator plug which is a low point. Kept the rust away.... An amusing after effect is that when a scanner is connected you are offered a choice of both VIN numbers. "It's not a ringer officer - just crazy modern electronics". Thanks for everybodys help and now onto the CDC Error..

 

[hofnerpres1]

Amusing epilogue. Following on from the above the car keeps starting very well. The old oil soaked ECM has been stripped and washed out with Iso Propanol. I'm currently chasing the next fault ( Engine warning light due to Air/Fuel ratio fault) and needed to eliminate the replacement ECM by simply plugging back the old unit and reading out the MAF values. They were the same 18 grams at tickover - should be less than 10. Nice to have a handy spare since it's a two minute swop on this engine. Blow me - it started on the key so the whole saga has gone full circle and I have a CLK with fully functional spare ECM. I can think of a number of reasons why but I'll let somebody else guess and just accept it as self healing good Karma. Next fault please !.....

 

[LostKiwi]

Amusing epilogue. Following on from the above the car keeps starting very well. The old oil soaked ECM has been stripped and washed out with Iso Propanol. I'm currently chasing the next fault ( Engine warning light due to Air/Fuel ratio fault) and needed to eliminate the replacement ECM by simply plugging back the old unit and reading out the MAF values. They were the same 18 grams at tickover - should be less than 10. Nice to have a handy spare since it's a two minute swop on this engine. Blow me - it started on the key so the whole saga has gone full circle and I have a CLK with fully functional spare ECM. I can think of a number of reasons why but I'll let somebody else guess and just accept it as self healing good Karma. Next fault please !.....

You're tempting fate saying "Next fault please"!!!