I would like to fire up the PCM I have and take a peek with HP Tuners. I have a OBD II connector and a blue PCM connector. Here is what I have so far:

OBD II

Pin Function
2 Serial data
4 GND
5 GND
16 +12V


PCM connector

Pin Wire Col Function
1 BLK PCM GND
2 LT GRN 12V Ref
19 PNK Ign pos voltage
20 ORN Battery pos voltage
40 BLK GND
57 ORN Battery pos voltage
58 DK GRN Class 2 serial data


I'm not sure if I need the 12V ref (pin 2), but if I supply a GND and 12V to the rest, I should be able to communicate to the PCM right?

I use this


Use alligator clips and you can attach it to any car battery

B2 is to the crank pos sensor, it is not needed for a PCM flash

Perfect! Thank you.

THAT'S pretty cool Pocket! (Dare I say FAQ-worthy?)

Well, It was a success... kinda. When I read the PCM, all I get is garbage. Not sure if this is my box or the PCM.

What did you use for a ground?

I tied all the grounds to the same point, the power supply ground.

Odd

I burned both my PCMs with that miniharness without issue. My tuner said that if the PCM was fried it wouldnt even read and yours is definitely reading. My power/ground were both to a car battery

It seems the main difference is my power supply. The other is that my switch to turn the box on, is on the ground side of the circuit... Because of the nifty lit rocker switch I used. I'd be shocked if that was the issue. I wonder if the 12v 3amp power supply I have set up doesn't have enough *****. Ill make an adapter for a the cigarette lighter and a set of alligator clips.
If that doesn't fix it, it can't be the power source.

The switch is for IGN power, not to interrupt ground. The battery cable isnt removed each time you shut the car off. I used a $2 switch from advance auto and it is doing fine. The fuse at the start of the circuit keeps everything from being burned up. Uber-**** people can put a relay in, but there relay isnt a need

Just a WAG, but an 110VAC power supply probably doesn't produce a clean 12VDC.

My switch position shouldn't matter. When on, everything gets power that is supposed to, which is fed from a fuse.

I just tried the power supply from my Xbox 360. Still a no go, in car with aligator clips is next.

I assume that even if a PCM was locked, I should be able to get further than this.

*Update*

I posted this on HP Tuners too. It seems I have a blank PCM. This means someone with a Tech 2 or take it to the dealer for a flash.

FWIW, I use a 12V 500mA adapter for an offboard to read GTP PCM's, I would imagine that's all you need for an LS1 also.