View Single Post
Old 06-11-2000, 12:21 AM
stevebfl stevebfl is offline
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
The 95 is kind of a weird year. It preceeds the OBDII diagnostics by a year although some models use it in 95 (the "C" class is one). I'm not sure but I think most systems on 95 124 bodies still use impulse counting. The diagnostic module (for emissions monitoring) is done by pressing the built in button in the same method as the following. The following is something I have saved so I don't have to write it again:

Over my few years responding to email for Mercedes Benz systems I have described a method for retrieving codes from MB control units with self-diagnostics. I have done this so often that I thought it might be appropriate to paste it here. I have told many to do this but I personally either use a scan tool or impulse counter. These
instructions are for those not having that eqiptment. They apply to systems before 1995 that can be read with an impulse counter.

Here it is:

The impulse method of code retrieval uses a box that counts and sums electric inputs. The input that is used is a switched ground. One proper method (which I have used) is to wire a led (light emitting diode) between batt positive and the diagnostic socket in question. . Once the diode is wired in place, turn on ignition (the diode might blink once but it shouldn't be
lit) and with a second jumper wire short the diagnostic terminal (which you are checking) to ground (the led will of course light during this event. Do this activation for
2-3 seconds. After a brief pause the ECU being addressed will send its ground signal output. One pulse means you have no faults, any other number describes a particular
fault code. Do you have data to decipher the code?

After the last pulse of the string and you have written the code number down, initiate the sequence again. If you get
the same code that was the only code in memory. If you get a higher number (the lower numbered codes will come out
first) write it down and repeat until you get the first code to repeat.

You now should have all your codes recorded. Now you should probably erase them and reread them to determine which faults are permanent (exist at the moment). To erase the code you start where we left off; having read all the codes and then re-read the first code. At that point short the diagnostic pin to ground for 6-8 seconds. Next do the retrieval initiation (the two second grounding), this will pull the
next code. Do the 6-8 sec erase procedure and then reread again and erase. Do this until all the codes you recorded have been erased. You will know this has happened when you again reread the code and you get one blink for "no codes set".

One should not do this unless you have appropriate service info to use the results and understand the system.

Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 06-11-2000).]
Reply With Quote