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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22911
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Hi I have 2006 slk200. It has done around 110,000miles, regularly

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Hi I have 2006 slk200. It has done around 110,000miles, regularly serviced, runs well, etc - but this morning it just stopped whilst driving after covering about 20 miles. En error came up which said coolant fault - high temperature go to workshop. After many attempts the car started for about 5 seconds then stopped. The car was left for about two hours so the engine was cool and still showed as being hot on the display. A second malfunction came up which said display fault. Diagnostics plugged in by a local garage that came out showed no faults and they just scratched their heads and said they couldn't fix it.
Do you have any ideas please?

I'd 1st check the coolant level ( hopefully this is OK) and I'm assuming that the engein isn't really overheating

and then move onto checking the coolant temperature sensor

as its very likley faulty

they can also have problems with the coolant temperature sensor connection plug getting corroded and also check the wiring for damage / heat hardened sections

Customer: replied 3 years ago.

Thanks, ***** ***** tried the temperature sensor connections and coolant level if fine. Engine is not really overheating. I have had a look at the temperature sensor and it measures around 2kOhms across the terminals which sounds about right to me. I am surprised that when the diagnostics reader is plugged in, no error is shown.


thanks Steve

Hello Steve

2Kohm with a stone cold sensor is about right but a warm(80 degC) sensor should be about 250ohm

I'd suggest replacing the sensor as they're quite cheap
Customer: replied 3 years ago.

I have replaced the sensor and checked wiring as far back into the loom as possible but stilll the same problem.

I am suprised that an apparent high temperature (or a genuine one) stops the car from running, so I am tempted to think it is a deeper rooted problem.


Thanks Steve

Hello Steven

Ok then its possible that there's a fault with the ECU module or the power supply to it

I'd 1st check the ECU fuses and also the condition of the small earth wires that run out of the engine bay loom and onto the engine
they should attach with a ring terminal and a small bolt

these are the ECU specific earths

if this is OK then I'd consider sending the ECU off for testing
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