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Old 07-11-2020, 06:17 PM   #1
rodstored-72
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OBDii connector

hi, I am trying to wire my OBDii connector and I am confused on what wires to connect. I have a 1986 C10 with a 2013 4.8LS stock engine. I have found the 2 data wires from the ECM (circuit 2500,2501 - tn and tn/blk)
1) tan/blk=2500 data 12v +
2) tan=2501 data 12v -

my OBDii GM connector:
1) pin 2 purple (data wire?)
2) pin 4 blk chassis ground
3) pin 5 blk SIGNAL ground
4) pin 16 org 12v constant on

this is my thought (understanding) of the connections:
A) conn pin 2 = circuit 2500 tn/blk wire (data 12v +)
B) conn pin 4 = ground to chassis
C) conn pin 5 = circuit 2501 tan wire (data 12v -)
D) conn pin 16 = connect to constant on power

I am just not sure on how & what to connect to install the OBDii connector?

any assistance would be greatly appreciated
thanks!
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Old 07-13-2020, 12:56 PM   #2
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Re: OBDii connector

Most of the constant voltage orange wires run through the cigarette terminal on the fuse panel but I would think any constant power fused source would work.
My 97 Grand Prix is wired like that.
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Old 07-13-2020, 07:55 PM   #3
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Re: OBDii connector

Vettevet, I was kinda of thinking that I would/could use my Cig wire for the constant on wire...hoping anyways
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Old 07-21-2020, 12:20 PM   #4
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Re: OBDii connector

well.. I have searched on a few other sites and still not able to tell what to do with the 2 data wires from the ECM. I do know that factory was they went "into" the BCM & then from the BCM there is a single data wire to the obdii "DLC".

any thoughts?? or "this is what I did"s????

thanks!!
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Old 07-22-2020, 12:00 PM   #5
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Re: OBDii connector

after doing some more research I have found the solution... I think
evidently later model GM vehicles (do not know the year change) have a updated communication language. the newer vehicles have what is called "CAN bus" and I guess requires 2 wires - hence circuits 2500 & 2501. the newer replacement connectors have a 5 wire pigtail. below is the connector I ordered. the CAN bus wires are included as well as the "regular" or older communication wire(s).

link:https://www.ebay.com/itm/142515602351

pin info:
2 20ga PPL CLASS 2 SERIAL DATA
4 18ga BLK GROUND
5 18ga BLK GROUND
6 20ga TAN/BLK CAN (+)
14 20ga TAN CAN (-)
16 16ga ORN BATTERY (12V)
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Old 07-22-2020, 03:10 PM   #6
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Re: OBDii connector

I have this recollection - but not even 50% sure it's right, so use at your own risk.

But, I think CAN BUS wires are "Concentric Twisting" from the factory. Check you original harness to be sure but I think its done to minimize interference. Here is some light reading if you are having trouble sleeping. https://www.hpacademy.com/technical-...tric-twisting/

I did some CAN BUS wiring in a Grand Cherokee and I think they were twisted. Just because Chrysler did it doesn't make it right, but enough to consider.

If anyone knows more, please correct me.
Thanks.
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Last edited by Wgesnerjr; 07-22-2020 at 03:23 PM.
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Old 07-23-2020, 10:24 AM   #7
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Re: OBDii connector

jay,
you are correct. the ECM data wires are twisted pair. I have lengths of additional color matching wire to "attemp" the twisting.... any hints/proceedures would be greatly appreciated

I tried last nite to use my drill.... not too smooth for first time trying...
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Old 07-23-2020, 11:40 AM   #8
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Re: OBDii connector

Glad I was not losing my mind remembering that.
I used a variable speed drill on a low. Keep the wires taught while spining the drill and they tend to come out better. Don't do too tight as they will start to kink.

Also, for anyone wanting more info on "Twisted" wire. Check out this other thread on Drive-By-Wire throttles and the TAC.
http://67-72chevytrucks.com/vboard/s...d.php?t=789749
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Old 11-14-2021, 12:45 PM   #9
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Question Re: OBDii connector

well bringing this back to the top.. aarrgg.. I tried to read the ecm & HP Tuners indicates that the port has power, but it can not "wake up" or communicate with/to the ECM??? I think I have the data wires connected right, but now not sure. I have been told that I do not need the "lscan" wire (pin 18 serial data wake up" from the ECM, but again not sure, it does not seem to make a difference in the lack of reading whether connected or not. I am at a loss right now.. I have "called in a few life lines" and to no avail!. hope fully someone on here.... IE ls1nova...LOL, can lend a hand...

information: 2013 4.8LS with OG trans, ECM,TCM,fuse box and factory wires (X1-X5 connectors). the obd port is a 6 wire new canbus connector pinned as below:
pin info:
2 20ga PPL CLASS 2 SERIAL DATA (pin 18 "serial data wake up" lscanbus wire)
4 18ga BLK GROUND
5 18ga BLK GROUND
6 20ga TAN/BLK CAN (+) hscanbus
14 20ga TAN CAN (-) hscanbus
16 16ga ORN BATTERY (12V)

Last edited by rodstored-72; 11-15-2021 at 11:16 AM.
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Old 11-26-2021, 01:30 PM   #10
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Re: OBDii connector

ok, so after finding out that what i had revealed that I had power to the port, but I did not have the ability to "read" the ECM. sooo.... after talking to a few people I realized I needed to re-do the 2 canbus data wires. In my reading I have learned that the "later" protocol for GM is J1850. Below is my latest attempt at the routing to get the port to work.

pin info:
2 TAN/BLK j1850 CANbus (+)
4 chassis ground
5 signal ground
10 tan j1850 CANbus (-)
16 battery (+) const on
-- all other ports are designated to be empty

If I understand right there should be a total of 5 wires connected, instead of the older more typical 4-wire connector. I will see if I can get the port to read this configuration & let you know....
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Old 11-27-2021, 10:13 PM   #11
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Re: OBDii connector

mann, this makes my head hurt...

instead of asking uncle jimmy's cousins dog walker for help, ask for diagrams... then you know...100% without a doubt.

pin 6 and 14 should be the communication 2500 and 2501.

swapping and trying stuff without knowing is asking to short out something.

what is pin 6 of OBD port connected to.... what ecu pin or transmission pin exactly? same for pin 14..
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Old 11-28-2021, 01:22 PM   #12
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Re: OBDii connector

I understand, if you are frustrated, what do you think I am... I have the 2013 engine diagrams & I had the obd2 port connected as you indicate and as described in the factory DLC port diagram (pins 6 & 14) as shown, but when I had the HP tuners (friend's laptop) plugged in, the ECM was not being turned on/ recognized?? I have looked on the internet and have found the information as detailed in earlier posts... the latest I have found was what I currently have connected (pins 2 & 10 for the data wires: 2500 & 2501). I am asking on here in hopes that someone else who has done a LS swap with a similar engine (2010 or newer) WITHOUT using a aftermarket harness might be able to help me, as well as I am hoping that the information I find out and works might help someone else in a similar situation. If you have done this or have past knowledge of what works to get the correct port wiring then please share... it might be helpful to others as well. I am gladly willing to admit that I am NOT a car electrical guru..... I have asked a few helpers of mine that are more knowledgable & they... along with shop owners have indicated they too are not sure why it is not recognizing/turning on the ECM. Unfortunately most people's experience is using a aftermarket harness so this was already pre-wired (why not used is not needed for this discussion). I apologize if I do not know the correct terms or I am not able to describe in correct terms, but like a few other people I am just a average guy trying to build something in the typical home garage.
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Old 11-30-2021, 10:49 PM   #13
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Re: OBDii connector

Well…after more research & talking with my friend with the hp tuner software, not to mention nudging from a few board members… I FINALLY figured out the correct pin assignments to read the ECM!...
below is the obdii port pin out. This is for a E38 ECM from a 2013 chevrolet Silverado.
Pin 1 thru pin 3= empty
Pin4= signal ground
Pin5= chassis ground
Pin6= ECM pin28 (2500) tan/blk canbus(+)
Pin7 thru pin13= empty
Pin14= ECM pin27 (2501) tan canbus(-)
Pin15= empty
Pin16= batt. (+) const. power
For me I used pin J5 from the “X4” connector (640) red/wht wire for pin 16.
Thanks to 87chevy.com for the nudge to recheck everything again. I hope this will be a help to others and thank you all for the replies.

Last edited by rodstored-72; 11-30-2021 at 10:54 PM.
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Old 12-01-2021, 09:25 PM   #14
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Re: OBDii connector

I dont have alldata access on this computer... do you have a 6l80e?

if so, probably the best spot to get the obd connection is at the transmission.... from this diagram, that might or might not be the same for your truck, its just one i found on lt1swap.com, those 2 wires, your splicing into..



these are similar to the gen5 swap harness I rework... can bus wires goes out of ecu, to trans, and trans out to BCM... in my swaps, i just use that BCM wire to OBD ports 6 and 14.. just splicing into the data stream may or may not lead to problems?

clint

Quote:
Originally Posted by rodstored-72 View Post
Well…after more research & talking with my friend with the hp tuner software, not to mention nudging from a few board members… I FINALLY figured out the correct pin assignments to read the ECM!...
below is the obdii port pin out. This is for a E38 ECM from a 2013 chevrolet Silverado.
Pin 1 thru pin 3= empty
Pin4= signal ground
Pin5= chassis ground
Pin6= ECM pin28 (2500) tan/blk canbus(+)
Pin7 thru pin13= empty
Pin14= ECM pin27 (2501) tan canbus(-)
Pin15= empty
Pin16= batt. (+) const. power
For me I used pin J5 from the “X4” connector (640) red/wht wire for pin 16.
Thanks to 87chevy.com for the nudge to recheck everything again. I hope this will be a help to others and thank you all for the replies.
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1999 BMW 528i - 5.7 LS1 w/ 4l60e, Ford 8.8 IRS w31 spline posi & FX-r projector retrofit

New project: 2006 BMW x5 6cyl AWD to L83 6l80e 4wd to 2WD / RWD

A poor man buy's it twice

finally got my domain name back, 87chevy.com.... site rework in progress
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