I am looking for input on intermittent issue with my new to me 2016 SL400. While driving the speedo and tach drop to zero and all warning lights come on and the chimes sound. This all happens in a split second then goes away and all systems seem to be normal. It only happens occasionally and not every day. My AD is having a hard time pin pointing the issue and is telling me that they have contacted techs at factory. Maybe the Electronic Ignition System module? Anyone else experience this issue? Your insights would be appreciated.

 

What were the DTCs when they scanned the vehicle?

 

I do not know. My dealer has had the car for a month. Latest is that they are sharing data with factory techs in Germany. Apparently the car has 52 modules. They have narrowed it down to one of six. I only talk with service advisor and never to techs working the issue.

 

Intermittent problems like this are near impossible to diagnose -- whatever triggers the event is uncertain and can't be induced to trace to a cause. Are there any circumstances you can identify when this event occurs? Hitting a bump, accelerating, braking, turning, etc.? If not, and the dealer can't figure it out, you might have to just drive the car until the problem becomes more pronounced, unless doing so presents a safety issue.

 

Make sure the tech checks all the ground points on the engine for looseness or corrosion….
Does it happen when the car is cold? Or always when hot? Mileage?

It would help to have any triggered codes for more direction though.
Intermittent electrical issues are tough to diagnose. Got to catch it when it’s misbehaving…

Good Luck.

 

Does the car stop when this happens, or does it just continue as normal. It does sound like a loose power or ground connection, as @crconsulting indicated.

This is why you need your own Mercedes-specific scan tool, XENTRY being preferred. I respect the dealership, BUT standard operating procedure is usually to replace instead of repair. So, they may only be looking for the LRU (lowest replaceable unit) rather than cleaning a ground contact, etc.

 

We don't know what fault codes are present, but assuming they are ESP related, here are the tests the technician should have performed.

 

There are about a bazillion potential faults associated with the ESP module. See attached. They may help direct your understanding of the problem and what is available to the dealer to fix things. Of course, your problem may just be with the Instrument Cluster and not the ESP at all.

 

I'd try turning off ESP when you start the car and see if the symptoms go away.

 

Here is the process the dealer should be following. I don't know your specific configuration and I am using XENTRY Simulation, but this gives you an idea of what the dealer has available to solve this problem. There are specific tests, etc. for each control unit identified.

 

If I select ESP instead of ABS, more control modules are involved. (ABS is a functional component of ESP.) It looks like three additional control modules are involved when evaluating ESP compared to ABS. Of course, if you don't have one of those modules, such as the AMG DRIVE UNIT, it won't appear in the list of modules.