Carl's Track Goblin - 05 SS SC donor, Chassis # 39

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Briann1177

Goblin Guru
It looks like the "Class 2 Serial Data" is a dedicated diagnostic line. I wonder if you have those two green wires connected together somewhere? I don't think you should have continuity between pin 1 and pin 2 of your OBD2 port since they're completely different circuits.

Just a quick thought to check.
 
Waterdriver

Waterdriver

Goblin Guru
Briann1177 said:
I pulled up the OBD2 port connector for an '05, and it looks like there is only one positive wire. There are two grounds however.

It also looks like the LSJs have two dark green wires right next to each other in the OBD2 connector. One is for low speed GMLAN and the other is "PCM Class 2 Serial Data (LSJ)". Not sure what the latter is. I wonder if something got mixed up when you removed the splice pack?

I believe the only thing in common between your OBD2 port and the gauge cluster is that green wire on pin 1.

I can't explain why your gauges work when you have your scan tool plugged in. That's very odd.
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I'm thinking that when I plug that Bluetooth adapter in, its connecting some of those OBD2 connections together.

I'll check both those grounds you mentioned for continuity first to see if that might be the issue. Seems like a lot of issues people come across are related to grounding or lack thereof.
I would think that if it was GMLAN or other communication wiring issue, the gauges wouldn't work with or without the Bluetooth adapter. I think that adapter might be providing/jumping the ground the gauges need to work.
Thanks for looking into it and the recommendation. I'll post what I find out.
 
Waterdriver

Waterdriver

Goblin Guru
On another note, I finally parted ways with the donor.
20180507_122525.jpg

Got a whopping $56 for it. It sure made my wife happy to see it go.
 
Waterdriver

Waterdriver

Goblin Guru
First start video.
Issue was the MAF was backwards to airflow. Flipped MAF tube around it idles like it should now.
 
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ctuinstra

ctuinstra

Goblin Guru
Ben Eldridge-Peter said:
Im having trouble parting out anything.
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Don't feel bad. I answered a lot of requests and priced many items only to not sell a dang thing! I got tired of all of the idiots just kicking tires and wasting time. I did sell the wheels and tires just recently, I kept them thinking I was going to use them on the car but didn't.
 
BaltimoreHokie

BaltimoreHokie

Goblin Guru
ctuinstra said:
Don't feel bad. I answered a lot of requests and priced many items only to not sell a dang thing! I got tired of all of the idiots just kicking tires and wasting time. I did sell the wheels and tires just recently, I kept them thinking I was going to use them on the car but didn't.
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I sold about 1k with of stuff. Almost my donor cost. I still have a decent amount but no interest. Takes up space and aggravates me when people request info that's already in the listing them never respond.
 
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KJP

KJP

Well-Known Member
BaltimoreHokie said:
I sold about 1k with of stuff. Almost my donor cost. I still have a decent amount but no interest. Takes up space and aggravates me when people request info that's already in the listing them never respond.
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This was my general experience. I think it has to do with most of these being owned by high school kids. I have however sold enough to cover all but 450 of my donor including the cost of picking it up and registering it. I still have some parts eating up space. I will give it a bit longer before I just throw away or scrap them.
 
Waterdriver

Waterdriver

Goblin Guru
Briann1177 said:
It looks like the "Class 2 Serial Data" is a dedicated diagnostic line. I wonder if you have those two green wires connected together somewhere? I don't think you should have continuity between pin 1 and pin 2 of your OBD2 port since they're completely different circuits.

Just a quick thought to check.
Click to expand...
Last night I was doing a little wiring diagnostics starting at the OBD2 port. Ground wire has a good ground.
Green wires, no continuity between them.
Started checking ground wire to chassis points back to the negative battery cable. Found that the ground cable I have attached to the pedal box was showing a low value of resistance.
Removed that cable, cleaned paint and primer off the mounting point and reattached.
The tachometer is now working but the speedo is showing a value as well. Could be the trans is freewheeling at idle since the axles aren't in at the moment.
 
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Briann1177

Goblin Guru
You want a low value resistance when it comes to ground wires. The lower the better. I don't think the build videos mention this, but yeah, you definitely need to clean paint or powder coat on the area where the pedal box mounts to the frame. Just cleaning where the grounds attach to won't be good enough.
 
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Briann1177

Goblin Guru
I'm also glad you figured it out. Ground issues are a ***** to troubleshoot, but fortunately they're easy to fix. Good to know you didn't have something cross wired like I was thinking.
 
Waterdriver

Waterdriver

Goblin Guru
Briann1177 said:
You want a low value resistance when it comes to ground wires. The lower the better. I don't think the build videos mention this, but yeah, you definitely need to clean paint or powder coat on the area where the pedal box mounts to the frame. Just cleaning where the grounds attach to won't be good enough.
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I had checked that ground before when bolting that ground lug and it read zero resistance.
A low reading of resistance is resistance to a good or complete ground for a ground wire. A zero resistance ground reading on the multimeter is a good ground. Unless of course your measuring a ground through a resistor. :)
 
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Briann1177

Goblin Guru
Don't let a zero resistance fool you. It could have been making contact through a tiny chip in the paint or whatever causing it to just be flaky enough to make you think it's good but still cause a problem.
 
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