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Hi all,
Just thought that I would drop a quick update on my CLK430.

The problem started intermittently, and symptoms were that the car would not "crank"
To try and alleviate a few "rumors" about how the ignition system and key works, please read the following.

( for those who are not interested in the complexities of why, the fault was with the shifter mechanism.)


Symptoms.
1 Key ( remotely) locked and unlocked the car and boot etc.
2. The Instrument cluster has a solid “white” block displayed, which normally shows the selected gear, ie P, N, R, D(1,2,3,4)
3. The gear selector moved between gears ( with your foot on the brake etc as per normal)
4. The key Turned, however NO engagement of the starter ( CRANNKING). There were a number of “clicks” heard under the dash, however these were not the start relay.

SO, after literally 18 months of faultfinding, downloading of wiring diagrams and discussions with Mercedes Technicians, and small South American rainforest worth of Trees.
The following information is provided in the hope that a few of you will get a better understanding.
(The Mercedes tech did believe that the shifter was the fault, however the AUD $1955 price tag for a new shifter, was not on my immediate to do list. I did eventually purchase a NEW shifter from a company in the US for $425 plus $80 freight (UPS) to Australia)


Ok -
MYTHS....
The Key FOB - has 2 basic functions.
1. As a remote - to unlock the doors / boot etc.
This function relies on 3 things. The little button battery, the bulk of the circuitry (as an IR transmitter) and the little red lens in the end.
• The Battery, when flat, will not unlock the doors.
• The circuitry when damaged will also not unlock the doors.
• The Little red plastic lens, which hides an IR LED, does not need to be “unscratched” etc. The LED is good for 10,000Hrs and VERY VERY unlikely to fail. Its RED, to allow for increased distance. Clear would also work BUT you could look into the end of the FOB and it would be ugly. NEW plastics on the market are not as inhibiting to the IR signal, hence why most FOBS now are simply black etc.


2. As a KEY to start the car.
In the operation of the "staring" of the car, the fob Battery has NOTHING to do with the process. The battery can be completely removed and the fob will still start the car. The Little RED lens also has NOTHING to do with the start process.


So, Start process goes something like this.

1. Key is inserted into Electronic Ignition Switch (EIS)(Position 0).
2. Key is interrogated by the EIS, and the key returns a KEY CODE.
3. The EIS sends the KEY CODE to the ECU ( Via CAN Bus data, this is a data signal and NOT just a single wire )
4. The ECU checks the KEY CODE against its records and if a valid key, sends a KEY OK signal back to the EIS
5. The EIS on receiving the KEY OK signal, Unlocks itself, by retracting a small pawl (allowing the key to turn)
6 The key can now be turned clockwise to Position 1.
7. The EIS then generates a “Steering Column Un-Lock signal”, which withdraws the locking bolt on the steering column lock, allowing the steering column to be moved. ( This can be heard as a whirring sound)
8. The Key, can now be turned to position 2, which is the Accessories position. Power (12V) is now applied to a number of accessories circuits. Including the Transmission Control unit (TCU), The ECU, the Instrument Cluster and of course “The Shifter”
The Shifter contains a small computer, which does a few things, including identifying the “gear position”.

9. The Key is turned to Position 3 (Ignition or RUN)
10. The TCU, interrogated the Shifter ( Via CAN Bus) and the Shifter returns a “GEAR” position ( for a valid start, it must be either Park or Neutral) In addition, the Gearbox, via our mythical oil weeping connector, the “conductor plate” and its Park-Neutral lockout switch sends a signal to the TCU.
11. The TCU compares both the gearbox signal AND the Shifter signal. IF both agree, the TCU send a “OK TO START” signal to the ECU ( Via the EIS and the CAN Bus DATA).
12. The Key is turned to “START”
13. The EIS Sends a “START” signal to the ECU.
14. The ECU activated the “START RELAY” which powers the Starter.

The communication between the TCU, ECU, Shifter, instruments(Gear selection indicator) and EIS, is all achieved by use of CAN Bus data signals.
The Conductor plate is simple 12v and Earth signals
The EIS is the gateway between the ECU and all other CAN Bus components.

FYI – Mercedes upgraded the shifter in 2002 to rectify 2 faults.
1. The shifter uses a system of 6 feelers and 6 carbon tracks. These are used to encode a voltage signal to its little computer. This computer is the one that gets screwed up when it gets a drink !!
2. The second fault appears to be the ability of the shifter to hold its memory. The chips used do not cope well with flat batteries and hence why so many people develop issues after a long period of sitting in the shed syndrome.

The upgrade shifter is part number 202 267 0824 ( old number is 202 267 0424)

Ok – I think I have cover it all, While it has been very rewarding now that the car is working again, I cannot express how frustrating it has been being unable to use normal fault finding electronics due to the CAN Bus data.
The Shifter did not send the correct data and threw no codes to indicate a shifter fault.

If the replacement shifter had not fixed the fault, the next step was to eliminate the TCU, then the ECU.

Great while they are working, but a pain when not !!!

Hope this helps, and happy to answer any questions etc....

Regards
Dave
 

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MY2000 W208 CLK320
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34 Posts
Thanks a lot for going to all the trouble to write that up. I'll make sure I can link to it in future. A Mercedes tech also diagnosed a faulty shifter in my 2000 CLK320, with the $2000 replacement quote. A different problem though - stuck in first gear, and the shifter would only move between drive and neutral. It only happened twice, and never since I cleaned the connector. BUT - can you tell me where you bought the new shifter unit, just in anticipation?
Thanks, Russell
 

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Premium Member
2004 CLK 240 Coupe
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11,377 Posts
I am impressed by your persistance and sleuthing here to nail your starting problem. I've never suffered this exact problem on my W209 - but I have tried using my WIS to help other posters here that are stuckwith a similar fault, and it is quite a maze of inter-connecting systems, I know.

A comment first on your 'start' explanation - followed by some questions.

1. I believe that the steering lock is actually released when the key is inserted in position 0. Otherwise your explanation is spot-on.
2. The fact that you could turn the key to the start position eliminated your remote key, EIS, DAS3 system, and the steering column lock. The start relay operated and the starter motor worked.

The situation when an engine is cranking but not starting should be easy to deduce but often isn't....surely it can only be a) no fuel (fuel pump?) or b) no sparks (engine control to ME-SFI not released?)

I have gathered together some WIS drawings that (I think) are associated with this fault, but I can find nothing that could definitely nail it down to the shift selector - except by elimination.

The signal that initiates the starter lock-out is, I believe, Y3/6s1 - pin 4 on the 13 pin connector to N15/3 (ETC control module) That information comes from electronic selector lever module N3/15 according to lever position P or N.

What I do not follow is how is the starter lock-out signal used to inhibit the engine start at ME-SFI control unit N3/10, where the ignition is managed? Does it go to a relay, or maybe to the cylinder shutoff solenoid valves? However it is formed, how can it be checked?

I have attached some WIS drawings on this topic.
 

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2002 clk320
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5 Posts
I replaced the shifter and the old symptoms are back!

I have followed all your posts and showed them to my mercedes repair shop, the car would not start in their own parking lot! The sifter would not get out of park. Anyway, I replaced it at a cost of $1,158 and it worked fine for a couple of days. However, today I drove to the park to go running and the car did it again, no crank, I sat in the heat for an hour and then it started like nothing was wrong. You said in your post that if the change of shifter did not work, you were going to look at the TCU and ECU, what are those? If my car starts Monday morning, I am driving right back to the repair shop and tell them to try again. Any help or suggestions would be greatly appreciated.
 

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Premium Member
2004 CLK 240 Coupe
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11,377 Posts
The OP said that changing his shifter module resolved his problem. He also said that the car would not crank. However, if he was able to turn the key from position 3 to START, the Drive Authorization System (DAS) must have permitted the key to turn. I am surprised that bad shifter did not stop the key in position 3, but I am not clear on the full operation.

I am aware that there is a signal that comes from the transmission ETC unit (N15/3) called 'starter lockout' which inhibits the Starter relay operation if the shft lever is NOT in P or N. However the position of the shift lever is generated in the shift module (N15/5) as stated by the OP.

So a fault in either could be another reason why the Starter relay might not operate. If it is operating, you can forget about N15/3 and N15/5 - so that is an important thing to establish early in your checks.
 

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Outstanding Contributor - Always Remembered, RIP
Zotye Auto 1.5T T600 2016
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52,804 Posts
The OP said that changing his shifter module resolved his problem. He also said that the car would not crank. However, if he was able to turn the key from position 3 to START, the Drive Authorization System (DAS) must have permitted the key to turn. I am surprised that bad shifter did not stop the key in position 3, but I am not clear on the full operation.

I am aware that there is a signal that comes from the transmission ETC unit (N15/3) called 'starter lockout' which inhibits the Starter relay operation if the shft lever is NOT in P or N. However the position of the shift lever is generated in the shift module (N15/5) as stated by the OP.

So a fault in either could be another reason why the Starter relay might not operate. If it is operating, you can forget about N15/3 and N15/5 - so that is an important thing to establish early in your checks.
He may have an EIS problem.
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
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As above, the steering lock goes off on inserting the key, if the key will not turn it has not been recognized by the EIS, so if it does not turn, either key or EIS, its that simple.
 

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2004 CLK 240 Coupe
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11,377 Posts
Guys - I think that this thread from 2012 is now very confusing.

The OP was not looking for answers - he had solved his problem - I just questioned his reasoning at the time.

Now it has been hi-jacked by someone who has another thread running on the W208 forum with a 'similar' problem. He can fully turn his key, but the engine is not cranking. It might be simple, but is not yet solved.
 

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Iv got mercades clk 230year 2000 w208 , i recently bought ecu kit off ebay because esl failed witch I was led to believe its coaded though have my doubts now, anyway replaced eis, esl. ecu was wrong one so tried it with origanal ecu and when insert key I hear esl disengage and it turns over but wont start???????
 
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