Possible OBD data issues?

[devianteng]

Hi all.

Donor is an 07 SS/SC, and I did my wire harness work back in Jan/Feb. Just the other day I did my first start, so overall things are good. I have a handheld scanner and was able to pull a few codes (mostly evap related, but I may have a dead/dying MAP sensor, or connection issue -- will troubleshoot that separately). Anyway, I grabbed my MPVI2 today, updated HPT on my laptop and went out to the garage. No matter what I did, I couldn't get HPT to connect to the ECM. I only had a few minutes to mess with it so it definitely could be an issue with my HPT setup, but I wanted to talk about the green data wires and the GMLAN wires.

I saw a mention previously in another thread that the SS/SC had a green data wire that you weren't supposed to cut, but the video doesn't talk about it. I'm 99% sure I connected all green wires to each other, and I'm second guessing myself if that was the correct thing to do. Also, I'm pretty confident that I connected up the GMLAN wires correctly, but I'm wondering if there are easy ways to validate that these things were done correctly (I recall reading something about checking resistance across the two LAN wires on the OBD connector, which I was getting like 61ohms across).

Any advice or tips how to start investigating/troubleshooting around data connectivity issues? Would I be able to start the car right up and see output on the dash if the data wires were wrong somewhere? I feel like if I can pull DTC with one scanner, then things should be good with HPT to connect but any advice is appreciated!

 

[Sluggonaut]

The quickest way is to connect another OBD2 scanner if you have one.

I think Fozda posted about the resistance reading across the ports and that continuity means problems.

edit: Found the post

Here's another one with a diagram and mentioning his fix.

 

[Ross]

The dark green wire that you aren't supposed to cut is only on our LSJ engine. It goes from pin 2 of the OBD2 port to the PCM connector C1, pin 16.

 

[jamesm]

When I did my LSJ harness, i accidentally connected the “extra” green wire to the bundle with the rest of them by the instrument cluster. Once I pulled it out and connected it to the proper OBD port, I could connect to all the computers

 

[escapepilot]

Derek - I made the same mistake on my 06 SS/SC. I had to cut the tape off the harness near the pedal box ground area and redo the green wire splicing. Ross' diagram should help you figure out which green is which.

 

[GoblinGuyZ]

Not sure this is relevant to your issue but still posting here for future users to potentially benefit...

 

[devianteng]

Thanks everyone for the great information, and links!

I quickly tested last night and I do have continuity across pins 1 and 2 on the OBD, so that tells me I connected them together. This weekend I'll peel back my harness tape and find those joints, remove pin 2 from that bundle and reconnect to pin 16 of the main harness ECU (blue) connector. Hopefully my issue will be resolved with that!

 

[Robinjo]

I just had to peel mine back a bit for something else and it wasn't fun. Wear gloves as everything is sticky.

 

[devianteng]

I just had to peel mine back a bit for something else and it wasn't fun. Wear gloves as everything is sticky.

I still have nightmares of the sticky mess I dealt with when working on the harness in the first place. Not looking forwarding to opening it back up...but it needs to happen!

 

[GoblinGuyZ]

Not sure this is relevant to your issue but still posting here for future users to potentially benefit...

View attachment 36925

So in trying to diagnose another issue I pulled my pcm and took a look at my C1 harness and it’s definitely not the same pinout. It’s the same P12 and the same connector in the bottom right of the pic above but the number 2, 7 and 19 points aren’t even pinned so clearly it doesn’t match up. If anyone else has an 06 LSJ and gets the chance to take a pic of theirs to cross reference would appreciate it.

My connector ….

 

[GoblinGuyZ]

Thanks everyone for the great information, and links!

I quickly tested last night and I do have continuity across pins 1 and 2 on the OBD, so that tells me I connected them together. This weekend I'll peel back my harness tape and find those joints, remove pin 2 from that bundle and reconnect to pin 16 of the main harness ECU (blue) connector. Hopefully my issue will be resolved with that!

Did you get it sorted?

 

[Gtstorey]

You need to look up the actual connector & wiring diagram for your models. Actual pin outs will vary with model and even options within the model.

 

[Ross]

I see pin 2 is in your C1 picture. It is on the lower right. Or do I have your C1 upside down? The left side (below) of the C1 block is longer...
Pin 1&2 are both part of the GM high speed LAN, so pin 2 will be on all 2006 LSJ Cobalts, no matter the options.
Pin 19 is ignition voltage - also on all LSJs.
You do know you have access to the wiring diagrams for a 2006 LSJ, right? (If you can see my signature at the bottom, it has a link to my index, go there and it is on Line 16: AllDataDIY Login )

 

[baustin]

When looking at the pinout chart Ross included and the image from GoblinGuyZ. It looks like pin 1 is in the lower right of the image. Pin #s are added here:

 

[devianteng]

When looking at the pinout chart Ross included and the image from GoblinGuyZ. It looks like pin 1 is in the lower right of the image. Pin #s are added here:
View attachment 37034

Thanks for the visual. The back of the connector have a few numbers showing which are which as well.

 

[devianteng]

Did you get it sorted?

Yes, I did get my HPT connectivity sorted. Easy, but time consuming, untaping and fixing my issue. I was able to connect with HPT, log, and pull my stock tune. Checking codes I was getting a code that sounds like a dying BCM but after looking back at my harness I accidentally cut 2 wires which probably explain that code, so I still need to fix those two and tape the harness back up. I did extend my coolant tank level sensor wires while I was at it so that was nice. Unfortunately illness has taken over my house and stopped me from working on the Goblin. I'll get back to it as soon as I can, but I'm 99% sure I fixed my original data issues because I cut that green wire (obd pin 2 to ECM pin 16) and added it to the other green wires.

Appreciate all the help!

 

[GoblinGuyZ]

Yea the first pic with the chart I posted is the back of the plug where the wires come out that you can see when the ecu is plugged in whereas my harness pic is the female end that plugs in to the ecu so everything is basically flipped

 

[devianteng]

Fixed a couple other wiring issues (extended another connector, fix 2 wires that I accidently cut) and my BCM code is now gone, good news!

Reviewing my previous HPT log and pulling codes, I'm now focused on my MAP sensor (getting a IAT2 reading, but no MAP reading) -- pulled the engine harness; need to pull diagrams and trace wires to make sure the harness isn't causing my problems. Also going to oder a new MAP sensor because why not. With this sorted, I'll have no outstanding issues and can move forward with my build!