2005 W211 220cdi - Non Start, no crank?

Alex Crow

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Right, Ive just removed relay L and checked for voltage. I have batt voltage on the middle pin of the relay which is numbered 5 but nothing on any other pins. Ive checked the other relays which are the same part number and have batt voltage on pin 5 and pin 1. So im assuming the pin 1 is the problem with no voltage. Ive checked F78 and F33 and have 12v both sides of the fuses and have 12 v on F42 but it doesnt appear to have a fuse for F34 :neutral:

The terminology "F33f78" refers to fuse number f78, mounted in the rear fuse box F33 (in MB speak, note upper/lower case f).

Please tell us the terminal name on the relay (eg 87, 30, 87a etc) where power is missing. You will find a diagram on the side btw.
 
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steve23002

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I am fighting here with my lousy eyes in reading the diagrams, I will try again today and see what I can find on F42.

I do not have the info on this computer, so hard to see the screen.

OK you have a voltage on one pin, thats ok in the fault condition as that voltage would be switched when the relay was energized.
See what I can find later

Brilliant. Cheers for the help :D

The terminology "F33f78" refers to fuse number f78, mounted in the rear fuse box F33 (in MB speak, note upper/lower case f).

Please tell us the terminal name on the relay (eg 87, 30, 87a etc) where power is missing. You will find a diagram on the side btw.

Right, I didnt know about that. I'll post a pic up of the relay in the morning. I thought it was strange as there are no terminal names on the relay. The relays came with the new front SAM from Mercedes and only have the PIN numbers on them. Just to confirm that the correct relay is L the 4 pin one in the front sam?
 
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steve23002

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Had a bit of a development today. I managed to get hold of autodata so have read the wiring diagrams. It appears that relay I is the engine control relay and powers f44,43 and f57. I have tested and have a 12v at both points of the relay. 12v at terminal 86 (pin 1 on the relay) and I have 12v on terminal 30 (pin 3. When the relay is plugged in I get power across terminal 86 and 85 which the supplies voltage to the ecu along the brown and yellow wire.
Im suspecting and internal ecu error as im assuming the ecu switches the relay via a switched earth...:confused:
I got brave and manually switched the relay and hey presto, all power to the ecu and the car will run. When the relay has de energised the car obviously wont restart. So my question really is does the ecu switch that relay? :lol:
If it does I will send the ecu away for testing. :D
 

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I make it that the f44 F43 are for internal protection for the ECU from the components they supply.

The thing to search for now is what energizes the coil on relay L
 

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Your car is it a 211.006
 

Alex Crow

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Sorry, my bad, I read it wrongly from the diagram as L, should be I.

Yes, the engine ECU switches this relay.

Good work so far, next...

Check the connections at the ecu (pin 44 Brown/Yellow) and SAM unit to be sure there is no missed corrosion.
I have seen a simiar scenario on a W210, where the ECU pin had corroded, and came away with the plug (this from another garage, they had no idea) - took a little finding, but was able to solder a lead into the ECU internally, to make the circuit.
This one was the same lack of power to the ECU, and was also an external switched relay (K40 module in this case) not being triggered.
 
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Yes the corrosion on these points Alex mentions are recorded in WIS as is the battery starter junction box on the floor in the cab where felt got mixed up with the terminal spades
 
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steve23002

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Your car is it a 211.006

Yes 211.006

Sorry, my bad, I read it wrongly from the diagram as L, should be I.

Yes, the engine ECU switches this relay.

Good work so far, next...

Check the connections at the ecu (pin 44 Brown/Yellow) and SAM unit to be sure there is no missed corrosion.
I have seen a simiar scenario on a W210, where the ECU pin had corroded, and came away with the plug (this from another garage, they had no idea) - took a little finding, but was able to solder a lead into the ECU internally, to make the circuit.
This one was the same lack of power to the ECU, and was also an external switched relay (K40 module in this case) not being triggered.

Removed all the connections this morning and all are good with no corrosion and good contacts. Voltage all the way to the ecu on pin 44 so it appears that the ecu is not switching :(
Ill arrange for the unit to be tested now.

Yes the corrosion on these points Alex mentions are recorded in WIS as is the battery starter junction box on the floor in the cab where felt got mixed up with the terminal spades

All the connections are good. Had them all apart and checked. :)
 

Alex Crow

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Just a thought, does the front Sam have to scn coded to activate? I know later ones do.

Might be this simple then ^^^^
 

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I would certainly go through the complete coding again, it does not take long, just to be sure the SAM has all the correct info
 
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steve23002

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Well, I sent the ecu away and they called yesterday and said the ecu is faulty, can be repaired. Should be back with me on wed, so I will update then :cool:
 

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Pleased we know, thanks
 
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steve23002

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The ecu arrived from BBA reman, plugged it in and it started 1st turn of the key. The car now drives and runs spot on. Only one small issue is a brake warning message which I think I created when I changed the front SAM unit. The ABS and SBS work fine, so ill have a look at that another day.

Thanks to everyone here for your help :)
 

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The wire for the pad warning goes via the front SAM but nothing in the SAM to upset it, it does not need STAR to put the warning out
 
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andy@pcd-ltd

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When the front sam was replaced was it coded to the vehicle as it might not have been coded correctly and thats why the brake warning light has come on.
 

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have had the same problem on e320cdi 2005 for over three years one minute works next will not leave it for an hour turn key and all is ok. if it does not crank it will come up with faults on dash like srs and abs which all disappear when it deciedes to restart but now warranty has expired mercedes believe is the ecu.
 


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