Source of info
General Motors (GM) OBD II diagnostic interface pinout and wiring @ pinoutsguide.com

Pin 2 should be +12V and not Ground to my understanding

when the ignition is off/run/ with engine stopped or running i get:

pin 16 = 12V
pin 02 = ground <<<
pin 04 = ground
pin 05 = ground

im pretty sure pin 16, 04 and 05 are all correct
its pin 02 that i believe is wrong

when i hook up my obd ii device (bluetooth) it tells me "obdii bus is shorted to vbatt or ground"

from the research i have done they say pin 02 should be +12v and the link i provided above also backs this up where it says "2 J1850 J1850(+) VPW"

if someone could either measure theirs or pull up a diagram so i can be tracing/troubleshooting this it would be great

i have another thread about slow acceleration and im wondering if this could be part of the problem.

i see a few fuses i think i can pull to try and isolate the circuit and they are "ECM-I", "ECM-B" and "ENG-I"

just not sure
if anyone could help out with this it would be great
btw i was also having a problem with my multifuncion switch and im wondering if that could also make that ground out to.

anyhow again any info would be great

 

i found a site that had some info on testing that DLC connector serial date pin.
Testing Serial Data Circuitry &mdash; WSU

it says i should get "The ohm meter should read "OL"" on my ohm meter between the data pin im interested in (Pin 2) and the (common data line ground) Pin 5.

im getting 75Kohms so i do have a short to ground.

Bummer!

it says i need to disconnect each module until the ohm meter reads OL

are the modules he is talking about the ones in the "body relay cluster" close to the DLC as seen in this picture?

https://i.imgur.com/JK5GC.jpg

its pretty cold out here in iowa (1F with windchill)
if anyone has any insight on where the short to ground most likely could be would be great.

i think i pulled down my "Body Relay Block for my 1999 blazer ls 4x4 (3button wheel drive)


removed all the relays in that Body Relay Block
disconnected the Multi-Function Switch by removing the 7mm bolt
i think i still have (1) two wire connector that is part of that MFS harness connected (up by the ignition cylinder)
removed all the fuses where you open the drivers door
removed all fuses and relays under the hood
and i still measure 75K Ohms from Pin 2 to Pin 5
any suggestions from anyone?

if someone could please check ohms on pins #2 and #5 of dlc with battery disconnected it would be great
im getting 75K Ohms
maybe that is supposed to be like that?

i removed all 3 connectors to the Body Control Module (BCM)
the measured ohms from Pin #2 and Pin #5 jumped from 75Kohms to 150Kohms
I plugged in the connector that is doing this, it is labeled "Brown" and it repeats
i moved that wiring harness around and the measurements do not fluctuate.

I disconnected all 4 connectors to the ECM under the hood (no change in measurement)
i really could use some help if anyone has the time.

here are quite a few pictures i took from under my dash showing the connections
(there are a couple connectors in the pics that im not sure what they goto)
ECM Related - Imgur

on some schematics that i have seen they say this is the SP201
https://i.imgur.com/QWYB1.jpg

but on some other schematics they say its by the IP fuse area on the right hand side

i disconnected the end in the picture above and im still getting 150K ohms from pin 2 and pin 5

this is driving me insane
its late right now and really cold outside so i gonna have to wait until tomorrow to try and find the "Real" SP201 because i think the one i just disconnected is incorrect

please help me someone