mjollnir

I'm figuring out wiring of a Silverado 2005 harness to plug my OBDII on. The wiring is out of any car and not connected to an engine for now. Just to its PCM and my laptop.

I have those wired:

Big red harness connector to +12V BATTERY
2 ground connectors to - BATTERY

PCM blue connector C1:
pin 1: grounded
pin 40: grounded
pin 20: +12V battery
pin 57: +12V battery
pin 58: SERIAL DATA (to OBDII connector pin 2)

When I connect my HP Tuners to it, I get a "Unable to locate VCM, please check ignition is on"

What am I missing?

aknovaman

iTrader: (7)

You need to connect the PCM power and grounds per this document. Looks like you don't have switched ignition connected. Look at the 99-current diagram.


http://download.efilive.com/Tutorial...20Tutorial.pdf

mjollnir

Thanks for input aknovaman

OBDII: pin 2 DATA ok
pin 4 GROUND ok
pin 16 +12V perm ok

BLUE pin 19 has 12V ok (wired to pink B10 on C2 Fuseblock)

My chinese voltmeter just died.. will get a better one tomorrow and continue debugging

mjollnir

BLUE pin 20 has 12V ok
BLUE pin 60 has 12V (should be GROUND per your document)

??

mjollnir

Aknovaman, do you have any idea?

Maybe wiring is different on silverado 2005 than on the document

gagliano7

Looks like you don't have the grounds correct if you have power on pin 60.By that document you should have power on 19 and 20 and ground on 60.Do you have the ground connected?

mjollnir

I have a ground from my harness connected to - of Battery. It's a quite thin wire.

Should I ground my fusebox somewhere?

On the wire side of pin 60 BLUE CONNECTOR, there is no wire connected. So the 12V comes from the wiring inside the computer (I did mesure directly on the pin soldered to the motherboard with the casing removed)

aknovaman

iTrader: (7)

All you need to communicate with the PCM via obd2 port is the following.
Blue connector, 19 - switched ignition, 20 -battery, 60 - ground, 58 - obd2 data line to pin 2 on obd2 port, obd2 port pins 4,5 ground, 16 - battery constant.

mjollnir

The problem is, if I ground pin 60 it will create a shortcircuit and could destroy my PCM

Joe1967ls

iTrader: (5)

I just finish modifying a 05 silverado harness using this site. I use HP tuners and engine is running on a engine run stand, hope it helps you out (i dont have a wire in pin 60)
http://www.lt1swap.com/2004vortec_pcm.htm
http://www.lt1swap.com/fuseblock_obd2port.html

aknovaman

iTrader: (7)

Go to chevythunder dot com and look at the schematics for your series of PCM for pinous.

gagliano7

I don't think the ground from the battery would work but i could be wrong.

aknovaman

iTrader: (7)

o the 05's the pin 60 is not used for grounding. he needs specific YR/model schematics to refer to for info.

mjollnir

Thanks all, I solved my problem!

I had a missing ground (a wire I wrongly labelled as "+" in the past) on pin 1 blue connector. I confirm for silverado harness: pin 60 blue connector has 12V but is not used.

Got to convert my injector harness, lube the engine and I can start it on the bench!