Hello all, I had recently purchased an 1994 E420 and I am loving it. I am a student, on a budget and I am trying to restore this beautiful piece of engineering to its old glory.

There are not many issues (from what my inexperienced eye can see) with the car beside from a rubbish paint job (done by one of the previous owners) and a few engine codes. Also there is a ticking noise that I belive may be caused by a hydraulic valve lifter that is not operating correctly.

I have the CEL (check engine light) On and when I use the built in LED flasher it flashes 6, 10 and 19 times.

It is my understanding that 6 means Idle speed control inoperative, 10 Voltage at Air Mass sensor too high or low and 19 stands for Fuel injectors-open or short circuit or Emission control system adaptation at
limit.

I am not to worried, because the car runs smooth and the fuel consumption is actually better than on my moms 99 Cavalier believe it or not.

The one that I am having a bit of trouble understanding is 6 Idle speed control inoperative.

I was wondering if someone has an explanation for what might cause this. Thank you for your time!

Welcome to the forum. You will need to go to this website K6JRF Auto Page at the bottom of the page and build the "Home Brew" DTC tester. The built in tester only tests the diagnostic module, which is pin 19 in that 38-pin cannon plug. You can check the other modules with the home brew tester.

A dtc 6 on the diagnostic module could mean a bad electronic throttle actuator, but there are other codes on several other modules that may help you diagnose the problem. In fact, there are certain codes on one of the modules (Pin 7) that can only be read with a digital tester, which is substantially more expensive. The digital tester allows you to better pinpoint the problem, but most guys (including myself) don't have one so we are left to throw certain less-expensive parts at it and hope it works.

DTC 19 on the diagnostic module could mean that the engine is old and it has exceeded the limits of adaptation that MB originally designed to set off the CEL. It shouldn't affect driveability but, if it really bothers you, that same website has a chip you can buy that widens the limits. DTC 19 is common on M119 engines as they get older.

The worst case scenario on your DTC 6 would probably be that your electronic throttle actuator (ETA) needs replaced. They all seem to go bad as they get old, just like the upper engine wiring harness. There is also an excellent website for the 500E, which is virtually identical to your car for repair purposes. *********

There is currently a member of that site who is dealing with a DTC 6 (accompanied by a limp home mode) and you may find that the website is a great supplement to this website. I enjoy reading both.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

Thank you for the reply and the useful links, I will try and build one of those blink readers and further investigate.

Cheers!