Troubleshooting OBD

Anyone had any experience working on the old OBD systems.
Having issues connecting to the diagnostics to obtain codes on my 95 Tacoma
As I understand it and maybe I am wrong but assumed that the OBD and onboard computer are 2 separate things and I am looking for a way to find the issue as to why I can not get my codes.
Is there a way to diagnose what may be an issue with my 16 pin connection? can I just go through and check each pin for continuity or voltage?

 

You do indeed Have a Tacoma not a Toyota Pick up?? What engine are you dealing with It makes a difference??

Stock truck no engine swaps?

The OBD system accesses the ECU /ECM the 2 are tied together. You really should Have the EWD for your truck.

Are you talking about the OBI engine diagnostic system ??That some early Tacoma`s used.

Not the OBDII system where you plug in a code reader under the dash right of the steering wheel

I need to look up some things it has been some time since I trouble shot a vehicle in that system.

 

95 Tacoma 3rz 4x4 with manual
have tried a few different scanners including having auto parts stores try and all get same results of failure.
my little innova OBDII reader has worked on this truck in the past and still works on my tundra
my check engine light is on and I am running very rich after very hard start ( have to use starting fluid). I have a thread running in the 1stGen forum of what I have been doing but figured I would start a new one regarding the fact I can not get my codes the problems may be related but this is a taco and one never knows.
and what is EWD?

 

Have you checked the terminals of the DLC?

Pin 2 is the data line to the PCM (Connector E5 Pin 7 (White))
Pins 4 & 5 should be grounded
Pin 16 should be full time power

 

Since your having a unable to connect problem have you cleaned both sides of your connection ??

I have had problems unseen corrosion cause no connection it makes things more interesting is that your meter probes get a good connection at times.

EWD is the Toyota Electrical Wiring Diagrams to me a must have for most all electrical work. Each vehicle can be different enough between years to get exciting.

Good Luck.

 

Can I clean it with basic electrical contact cleaner?