Access to Diagnostic OBD II Module on 96 c280

[Martineau Gauda]

Hi, I need to back probe some signals and voltages on the OBD II Diagnostic Module with Auto Multimeter.

It is designated as "N59/1" per Mercedes service data. This is the diag module where the signals come in and not the under dash OBD II connector used to plug in the readers for DTC. The O2 sensor input signals are available at this connection.

I believe the module is located in the cabin, but need to know where to look. Is the connector pins accessible without a special breakout adapter?

Thanks

[Arthur Dalton]

02 sensors plug is under the passengers side rug.

[Martineau Gauda]

Thanks that information is useful, but I still would like to access the OBD2 diag module itself as there are many other system tests specified by Mercedes, and Alldata that one can do with multimeter using this connector.

Thanks

[Arthur Dalton]

You mean the 38 pin plug under the hood.

[Martineau Gauda]

No not the 38 pin connector in the engine compartment. There is another unit, the OBDll Diagnostic Module that processes the signals for the OBDll connector. Both Mercedes service manuals and Alldata show procedures for testing at that point to diagnose specific DTC's with automotive type multimeter. Lots of valuable tests are shown with nominal range values and suggested actions. The connector is designated as N59/1.

Thanks

[Arthur Dalton]

N59/1 on that chassis is Digital DM/OBD2 Module, so I do not know how you are going to get any info from a MultiMeter.
If there were a connector . it would state X/- .... as X/27 or X/4, etc.

[Martineau Gauda]

That is the exact unit I am looking for. There must be a way to back probe because these are lots of tests specified for the 22 pin connector on that unit. Do you know where the unit is located?

I hope that the tests shown by Mercedes and Alldata do not require a special breakout box or connection harness to access the terminals.

Lots of measurable information goes to that unit and diagnosing DTC's at the N59/1 OBD 2 DM unit are referred to by the Mercedes service data.

Engine Speed signals, CMP sensor, purge flow system, DM pressure O2 1 and 2 sensor, and others diagnostics procedures refer to this connector in both official Mercedes service CD and Alldata.

Thanks

[Arthur Dalton]

I only see N59 for OBD1 on 124 chassis..it is 22 pin and it is located under dash, to the left of the steering column. There is no designated X connector , so you just unplug it to get to the designated 1-22 pins.

What does your Alldata say for location??????

[Martineau Gauda]

Arthur, I look under the dash and could not find the connector. Maybe it is behind the knee roll.
Alldata shows in in that general area.

I am leaning toward getting a used Snap-On MT2500 with Mercedes cartridge and cables. I have one of the older Actron OBDII code readers that works fine for pulling codes and I was looking at the Innova 3130 unit that claims to read a lot more from the OBDII. (Pending codes, live data, freeze frame) but I am unsure how useful the unit will be on the 96 C280 because of Mercedes proprietary nature.

Many thanks for all your help. I will keep looking.