I bought one of the DTC pushbutton testers/readers off ebay, supposedly for the 92 400e as advertised and I seem to be having great difficulty getting it to cooperate. I do in fact have a CEL that remains on constantly unless I drop the battery connection and sure enough, after four or five stop and go starts, the CEL comes back. So, I assume that I have a "hard" code. Hopefully just an O2 sensor. I have the 38-pin connector located on the right rear fire wall under the twist off cap and I am inserting the red lead into the power pin #3 and the black ground pin in pin #1. I turn the ignition to the on position with the dashboard lights on and without the engine being started. I begin probing the remaining pin sockets with the yellow lead with the corresponding button push for at least five to nine seconds and release. according to the seller, I should get either a flashing light of one pulse, indicating a normal condition or I should get a series of pulses corresponding to the indicated fault listed in the users manual which depicts the numerous systems on the car. All I seem to get as a result is the button mechanically remains in the down position and the red led light comes on and remains until which time I recycle the button to the up position and the led red light on the tester/reader goes out. With the led light coming on the reader I assume that I have followed the proper procedure in placing the red and black in the proper holes but, I am not getting any flashing of the led when troubleshooting the remaining pin sockets. I have gone through the three pages of the forum for this model and do not find a related thread other than the one that sent me to the tester/reader guru. Having read this one I am left to believe that my reader should work and it also showed a picture of a pushbutton reader incorporated into the car on some models. In front of my electronic box that contains the afore mentioned 38-pin DTC connector is a pushbutton panel similar to the one in the picture except that mine has numerals 1 thru 7 or 8 sockets/holes with a pushbutton and led light beside it. When I push that button down for about 5 or so seconds and release, all I get is a corresponding red light while the button is pushed down only and it goes out when the button is released. I have the ignition in the previously stated position while I do this as well. I know this message tends to be lengthy but, I wanted to provide as much detail so maybe one of you great peoples could assist me in getting out of this ditch I seem to be in. Your indulgence in this matter is greatly appreciated. Chief warrant Officer Four (CW4) William "Greg" Timmons, US Army Apache Pilot (CELL) 662-687-0703

 

make friends with this link! look under sections 2 and 6 it should point u to the right direction!! I know its not for a w124 400e but its the same engine (M119) best of luck and have a good weekend!