LOOKING FOR A BENCH HARNESS FOR A 1997 CHEVY LT-1 OBD2 TO BENCH PROGRAM PCM

[_LT1]

LOOKING FOR A BENCH HARNESS FOR A 1997 CHEVY LT-1 OBD2 TO BENCH PROGRAM PCM:

Does any one have a diagram or links to some videos for me. thanks

[steveo]

same as an OBD-I but different data pin

red connector: pins 2 and 18 ground
black connector: pins 15,30,31 power
gray/clear: pin 32 ground
blue connector: pin 1 ground, pin 3 power, and pin 7 is your OBD2 data

im sure all the grounds aren't that necessary but i connect 'em anyway

here are some diagrams (covers all 1994-1997 LT1 ecms)

http://shbox.com/1/4th_gen_tech2.html#1995_pcm_pinouts

[In-Tech]

What a great link, steveo.

Here is some more info that might come in handy.

LT1 OBD1/2
Red pin 2		Ground
Red Pin 7		Fuel Pump enable to relay +12v out
Red Pin 25		Fuel Pump enable VATS
Black Pin 6		Analog Ground	Black/White
Black Pin 15		12v Constant	Red
Black Pin 16		Analog Ground	Black/White
Black Pin 28		5v
Black Pin 29		5v
Black Pin 30		12v Switched	Purple
Black Pin 31		12v Constant	Red
Blue Pin 1		Ground		Black
Blue Pin 3		12v Switched	Purple
Blue Pin 7		Serial Data	<<<<< OBD2
Blue Pin 9		MIL
Blue Pin 20		Output/Field Service Enable (Diag Port) DLC Pin 6 ckt 448, ,Pin C C230
Blue Pin 29		Serial Data	<<<<< OBD1
Blue Pin 30		Serial Data	<<<<< OBD1

[Tom H]

For a bench setup, you might want to have a switch for the source connected to Black 30/Blue 3. The PCM doesn't power the processor and most other circuits until this ignition circuit is applied. When it is removed (key off), the processors continue to run until an internal reset is generated. There are several ways this can happen. Once the reset occurs, the Power Management IC (PMIC) removes power from most of the internals.

If you plan an "open case" bench setup, it is a good idea to connect grounds between the "T"side and "E"side. This grounding is usually taken care of by spring clips between the boards when sandwiched in the case. If you remove the boards from the case the ground needs to be re-connected. In most cases this will be OK just through ground connections to each half. Should you be drawing more current from some of the drivers though, a ground shift can happen and cause unexplained faults. To do this I just make bare some of the copper ground hatch and solder a wire between boards.

[In-Tech]

Tom, as always, valuable information :)
There should always be a constant BATT power and then IGN power via a switch since EVERY ecu does "housekeeping" on key off.