I will go over the problem I am having in more detail. The Check Engine light comes on after a few days of resetting it. I always get two codes: one of them is 19 (Fuel injectors open/short circuit or Emission control adaption in ECM at limit) and the other one at times is 3 (Lambda control inoperative) or 4 (Air Injection inoperative).

The vehicle operates flawlessly. Smooth idle, 22 MPG fuel ecnomy, no problems in starting, engine temperature stays between 80 and 95. Everything works fine.

I looked up the information copied below, but I do not think that it applies, because the dealership installed an ECM from another vehicle, and they claimed that everything was working fine after that. I believe that it is a minor issue; otherwise, engine performance would have suffered.

A different Mercedes Benz dealer after replacing the wiring harness was not able to find anything wrong with the vehicle, but the Check Engine light comes on.

60K miles service has been done. The car has new spark plugs, fuel filter, air filter, transmission fluid etc.




Mixture Preparation Self-Adaption


The Lambda control system determines fuel injection duration precisely so
that the fuel/air ratio is kept constant at Lambda level 1 (equals 14.7 kg
air to 1 kg fuel) under all operating conditions.

Should malfunctions occur in the form of:

Intake air teaks,
Injector wear or carbon build-up,
Engine wear,
Contact resistance in mass air flow sensor,
Defective diaphragm pressure regulator,
Defective purge switchover valve,


the engine control module automatically corrects the fuel/air mixture by
adjusting the fuel injection duration.

The degree of correction is constantly calculated and permanently stored if
the following conditions are satisfied:

Engine coolant temperature < 52 °C at start.
Engine coolant temperature between 80 and 100 °C while driving,
Intake air temperature between 0 and 55 °C.


Air/fuel mixture self-adaptation occurs at idle and under partial load. The
maximum degree of correction towards rich or lean is 25%. After fuel
injection system or engine repair work is performed, the engine control
module will automatically adapt itself after approx. 10 trips. After
eliminating a malfunction or after trial installation of an engine control
module from another vehicle, the self-adaptation feature must be reset (see
"Resetting and Reactivating ECM Memory").