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*Premium Member
1999 SLK230
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18 Posts
Discussion Starter · #1 ·
I hope I'm in the right space for request for some help and guidance please

History:
Bought our SLK 8 years ago as a non-runner
We found that the K40 was faulty and once replaced she was fine and has never let us down
The only thing we have done recently (last Tuesday) that might be linked to this fault was to power wash the engine bay, which we have done in the past without any problems, so might be a coincidence, but I thought I should mention it
Everything has been fine until we went to use the car on Sunday morning when the issue started
We love our SLK and desperately want to get her fixed

Issue:
Put key in ignition, turn on and all dash lights come on as normal
Turn to crank, engine fires and them immediately cuts out
Followed by instead of mileage showing on the display, it flashes "Start Error"
All other electrics on car are working as normal
When ignition is on, all the usual noises are heard including the fuel pump etc

Possible issues learned from this forum and steps followed to check them today

1) Battery has been fully charged on Optimate and tests as good
2) Fuses 35 & 37 removed, cleaned (had traces of oil on them) and re-installed - No change
3) Re-sync fob - No change
4) Tried spare key - No change
5) Re-seat K40 connections - Error stopped showing, but fault persists
6) Leave negative disconnected for 15 minutes whilst unlocking & relocking door - No change
7) Oil on cam position sensor connector - No oil on connectors, which were cleaned and reconnected, Start Error is showing again
8) CPS - Crankshaft Position Sensor - Re-seated connection, no change
9) Basic OBD diagnostics via Bluetooth reader and Torque Pro - Errors reported:
a. Pending Fault P0720 Powertrain - Output Speed Sensor Circuit Malfunction
b. Pending Fault P2000 Powertrain - NOx trap Efficiency Below Threshold (Bank 1)
c. No ECU errors reported
Faults cleared - No change
Re-ran scan and faults showed back up
As they are listed as "pending" I've taken it that they are not linked to my issue
10) K40 relay - Had a solder joint that looked dry/suspicious, replaced with spare relay - No change. Re-soldered joint on original relay and re-installed - No change

These are my next steps for tomorrow
Further OBD diagnostics with a better scanner that I'm borrowing which might pick up other codes

I have started to remove the interior trim from around the steering column, so that I can check the connections on the chip reader (Antenna) behind key barrel that connects in the immobiliser system

If I cant find a bad connection, or get anything useful from the OBD scanner, then I understand the remaining task is probably to replace the Antenna on ignition lock cylinder and linked parts of the immobiliser system as it is probably faulty ( ignition barrel, door lock barrel and ECU kit)

Any thoughts or further guidance please?

Thanks
Trev
 

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* Administrator (Premium Member)
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37,228 Posts
It may be coincidence, but as Tony indicates, some have had a lot of electrical trouble after power washing the engine bay. (He is one of our go to experts).

On the off chance of it being something else I'll shout @Dave2302

My apology for not replying earlier to an excellently detailed shout for help.
Somehow I missed this thread.
 

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*Premium Member
1999 SLK230
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18 Posts
Discussion Starter · #5 ·
It may be coincidence, but as Tony indicates, some have had a lot of electrical trouble after power washing the engine bay. (He is one of our go to experts).

On the off chance of it being something else I'll shout @Dave2302

My apology for not replying earlier to an excellently detailed shout for help.
Somehow I missed this thread.
Yes, looks good, thank you
 

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*Premium Member
1999 SLK230
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18 Posts
Discussion Starter · #6 ·
It may be coincidence, but as Tony indicates, some have had a lot of electrical trouble after power washing the engine bay. (He is one of our go to experts).

On the off chance of it being something else I'll shout @Dave2302

My apology for not replying earlier to an excellently detailed shout for help.
Somehow I missed this thread.
OK, I've learnt a lesson the hard way and I agree that by me stupidly power washing and the fault that developed within 5 days is more than a coincidence and clearly I've caused the issue :(

So, I've stopped pulling the dash apart and instead ran a further OBD scan with another scanner and it has returned the code P0720 Output Speed Sensor Circuit

Having looked here and on other sites/forums, I cant find a link between this error code and the start error I have, so yes, can I take up your offer of further help on my best course of action from here please?

Many thanks
Trev
 

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*Registered
2002 SLK32 (x1), 2003 SLK230 (x2)
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197 Posts
Power washing engine had nothing to do with this.

The Start Error message is a result of a security module failure. The part is a brick behind the instrument cluster, and in my experience was a dealer only fix. SDS may allow coding of the part, if it can be obtained.

When this happened to our SLK, it was taken to Dealership for free on a flatbed by dialing the 1-800 number in the glovebox. Mercedes of Plano had to get the custom coded part from the nearest Mercedes tech center, which happened to be Fort Worth.

In five SLKs and a quarter million miles in them, this is the only showstopper item we have had.
 

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*Premium Member
1999 SLK230
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18 Posts
Discussion Starter · #8 ·
OK, so I'm keeping an open mind on this

Its a 1999 SLK 230 R170 , which in the UK is worth around £1500 / $2000, but she has never let us down until now, so I really want to get her back on the road before her MOT expires in around 2 weeks time and be able to use her with the hood down this summer

I'm now retired, so have time on my hands, so would prefer to fix her than spend a lot money with the local (Exeter, Devon) Mercedes dealer

Yesterday, I tried another OBD reader, which again pulled up the P0720 error, which from all the reading I have done here and elsewhere, does not appear to link to the "start error" that I have. I decided to clear it for now, but have ordered an OSR wheel speed sensor based on what I have read and that will arrive on Monday

I also pulled the ECU (A 028 545 44 32) out and found a very small amount of what looked to be oil contamination and a couple of sockets with minor signs of corrosion. Carefully cleaned the terminals with a glass fibre pencil, sprayed with contact cleaner and dried with compressed air. Did same with plugs. Reassembled, but the error still there

I've started to pull the dash apart to access the security module to check its connections and grab its part number. Struggled to get the dial housing out, so decided to leave it and go back with fresh eyes today

The more I read, the more I'm leaning towards the immobiliser as the culprit and if its more that a bad connection, I think I will need to replace the security module, but rather than pay Mercedes to recode the part, I'm looking at buying an ECU & lock set with matching part numbers from a breaker for £245

Any further advice from anyone would be greatly appreciated
Many thanks
Trev
 

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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6,604 Posts
What you need to do is to forget about OBD rubbish and get the Car on SDS, that will be able to tell exactly why it won't start and save you a fortune in wasted time and parts.

Why does that sound harsh .............

Because no R170 is OBD Compliant ...................

Analogy ....

Imagine the network of circa 15 separate Computers (on most R170's) as if each one is a House in your Street, and now imagine you are trying to see what is going on in that Street through your Letterbox, you simply cannot see all that is happening inside all ;)

This is why SDS is so important for serious DIY work as well as professionals :)

I don't recommend using Dealerships for this service, either bite the bullet and buy a decent Clone SDS or get a good trusted Indie to do a thorough SDS Session, which can take up to a couple of hours time ;)
 
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*Premium Member
1999 SLK230
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Discussion Starter · #10 ·
What you need to do is to forget about OBD rubbish and get the Car on SDS, that will be able to tell exactly why it won't start and save you a fortune in wasted time and parts.

Why does that sound harsh .............

Because no R170 is OBD Compliant ...................

Analogy ....

Imagine the network of circa 15 separate Computers (on most R170's) as if each one is a House in your Street, and now imagine you are trying to see what is going on in that Street through your Letterbox, you simply cannot see all that is happening inside all ;)

This is why SDS is so important for serious DIY work as well as professionals :)

I don't recommend using Dealerships for this service, either bite the bullet and buy a decent Clone SDS or get a good trusted Indie to do a thorough SDS Session, which can take up to a couple of hours time ;)
Thanks Dave
I will check around Exeter for an auto-electrician
I presume I need to ask that they use SDS, or is that a standard?
With regards to sourcing a clone SDS, have you any pointers please?
Thanks again
Trev
 

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*Registered
2002 SLK32 (x1), 2003 SLK230 (x2)
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197 Posts
When our SLK had this failure, Mercedes charged $1000 to replace the failed brick, and this included tax and the free tow. it was expensive to me, but easily solved and we were back to enjoying the car in a few days. It is possible the issue could be the key reader ring in dash, which is less.

Your idea of swapping ecu, security brick and key reader might work..but if not you are that much farther into it and closer the same as paying the dealer to fix.

I do most all my own work on 3 R170 SLKs (2-230s, 1-SLK32), and this one problem best tackled by experts with the right tools.

Hoping you are back to top down motoring, soon.
Regards,
 

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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I don't think it has anything to do with Drive Authorisation, I think it has water in 1 or more critical components, but without the right kit to lead you to the issue, anything else is pure guesswork / lottery.
 

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2002 SLK32 (x1), 2003 SLK230 (x2)
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197 Posts
Will be interesting to see a proper SDS diagnosis.
Love a good detective mystery.

When I had the Start Error fault, I had a lengthy conversation with the Mercedes tech on the phone, prior to them sending the truck to pick up the car. it was a security problem, for sure. And that is what Mercedes fixed.

Now, if one wanted to go down the path of coincidence about the pressure washing, theoretically water could have confounded the communication between the modules. But the ECU is in two layers of a protected box, and the pressure washer surely didn't get the box in the dash wet (Mercedes made these almost goof proof on purpose). The wiring should be waterproof, unless compromised by rodent damage or some other physical damage by wear.
In the US cars the ECU box is adjacent to the battery, remove the battery and look under the ECU box and at wiring to see if any damage, and check the grounding block adjacent to battery. Bad or corroded grounding can be the source of many issues.

The problem is either right under your nose or its the security brick.
I'll bet a trip to the pub on it. ;)
 

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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When I had the Start Error fault,
Did I miss something in one of the posts ? Highly likely atm ;)
Is the OP's Dash displaying "Start Error" ??? ........................

If so then yes that would be Drive Auth, (Immobiliser), related, but I was under the impression he pressure washed the Engine Bay, then it didn't start ?????????????????

Hell IMHO as a Technician (of millennial years now), it actually beggars belief that anyone would do that, but I usually shake my head in disbelief as loads of guys do do that some get away with it if they are careful, most don't ;) ...............
Might as well power wash your TV and Hi Fi in yer living room too, see what happens then ....... but I digress 🤣

The 3 Theft relevant parts are the Motor ECU which is in a Plastic (sorta Splash Proof) Box under Engine bay ................ Suppose it could be that if the Box was blasted, and then there is the Key and the DAS / RF Module, which usually reside inside the Car well away from any water ;)
 
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2002 SLK32 (x1), 2003 SLK230 (x2)
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Indeed, the initial post states there is a "Start Error" message in his dash.

So as suspect/cringeworthy/coincidental as the pressure washing was, my opinion and personal experience with same error message is pointing to the security module or related hardware as source of the problem.

Question to Dave: If there was an intermittent fault that tripped the "start error" message, is this a resetting fault ? Or does the immobilizer permanently disable the vehicle?
When I had the issue, it couldn't be reset by battery disconnect or waiting.
 

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*Premium Member
1999 SLK230
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18 Posts
Discussion Starter · #17 ·
OK, thought I should add an update on progress
Whilst not yet on SDS, we have pulled the following fault code - P1570 faulty DAS to the ME - SEI
The plan was to talk to the Independent Merc Specialist in Exeter next, but before that was done I continued with my checks on fuses, connections etc and by chance saw some corrosion through the plastic body of the Headlight Control Switch (A1705450504) and decided to pull it apart to find as per the pic
602155

It does clean up, but no doubt it is pretty bad inside, so I have ordered a replacement from a car breaker, which is expected to land next Wednesday
So, things are on hold until it arrives and has been fitted
Will get back here with a further update next week
 

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*Premium Member
2001 SLK200K/2001 SLK320
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Never seen one that bad, I've said it before, they are becoming a problem 🧐

There's a lot going on inside that particular module, mine caused my engine to not stop for example ~ even with ignition off and the key removed that ol' engine kept on a running :alien: 🤷‍♂️
 

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*Premium Member
2001 SLK200K/2001 SLK320
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3,032 Posts
BTW. Engine on mine stopped and started just fine once that module was disconnected and out of the car. Dunno if that helps or not but it did prove that that was stopping it from stopping, so to speak. I have no idea why :p 🤷‍♂️
 
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