PCM Programming Harness
 

 Pease feel free to let me know if you have questions, or if you have comments!

I had always wanted some method of programming OBD-1 and OBD-2 PCMs

for our Impala SS Club vehicles that removed the risk of having

bad battery connections or low batteries 'fry' flash modules

in PCMs.   This had happened to us on a recent Dyno Day while

Bryan Herter of PCMForless ( our favorite tuner ) was tuning some

 of our vehicles with our favorite tuning software TunerCat !

  TC is VERY responsive to the LT1 community and many others!

Here is a short write up and picture showing this cabling 'rig'

The power supply which feeds this must be no lower than 12.5 volts when loaded.   I 
purchased a power supply from Radio Shack p/n 22-504.  $39.  Works good.

(Plug that into a small UPS and you are fairly safe!)

This power supply puts out 13.5, so I cut it down with two 1N4001 diodes in series with the negative lead.   It runs right at 12.6 with the PCM powered up.

When +12 and GND indicated below, this is the + and - side of the power supply.

I have both a DB9 connector and a DB25 on my cable.   The DB25 will go
right to Andrew Mattei's OBD-1 programming cable, and the DB9 talks
right to CarPuting's LT1 Edit OBD-2 VIN detecting 'dongle' or 'wart'.

NOT doing the OBD-2 DB9 simplifies this cable a lot.  I put it in just
to make the cable completely capable of doing both OBD-1 or OBD-2 programing.

I got the basic info from for this cable from Andrew Mattei's website.

Andrew was a HUGE help getting the DB9/OBD-2 end working!!

And TC at TunerCat was like my penpal at times... even

drawing up the schematic for me and sending it back in a .pdf file!!

Parts sources are RADIO SHACK or DELPHI

The connectors I refer to are at the PCM end, and I refer to them by color.   The pin numbers are marked on the back of each one, you may need a magnifying glass, at least if you are OLD like me and half blind....


Conn/   PCM             Connect To      
Pin     Wire Color
------  --------------- -----------

BLUE

D1      black/white     GND

D3      pink            +12v

D30     tan             OBD-1 Serial Data to DB25 pin 5

D7      purple          OBD-2 Serial Data to DB9 pin 7


BLACK

B15     orange          +12v

B31     orange          +12v

B30     pink            switched +12v - ALWAYS ON for OBD-1.

                                    CAUTION
                        SWITCH on AFTER turning on the power supply for OBD-2 PCMs.
                        This is the toggle switch on the Budd box, Don't fry a PCM!

Update:  Thursday 7/31/03:  TC from TunerCat is going to show me a way to wire this without using the GRAY and RED connectors.   Two less connectors is GOOD!    So stay tuned....  ( no pun intended )    

Here is the schematic for the TWO connector OBD1 / OBD2 benchtop programming harness.

( TC from Tunercat whipped this up in 2 shakes!)

GRAY

C32     black/white     GND


RED     

A18     black/white     GND

A2      black/white     GND



DB9 - OBD2 data connector

1       GND
2       GND
7       Data ( from BLUE D7 )
9       +12v

DB25 - OBD1 data connector

1       GND
5       Data ( from BLUE D30 )



I put a small Budd box in series with all this to 'hide' my wiring, and have a place to mount my +12v switch ( delayed power I call it ), for the OBD-2 PCMs.   If you don't switch this one line, you'll SMOKE the OBD-2 PCMs.    Andrew says he's not sure why, but trust him.... he's done a LOT of these puppies.

Gerry
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gem 05 Dezember 2006 08:24:10 -0500