I’m having an issue getting my OBD2 port to work on my LS6 powered Europa. I’m using a stock GM computer and wiring harness from a 2004 truck. The engine runs fine, but when I try to connect my scanner, it connects, then runs through the protocols, but at the very end gives me a “linking error” message.
When I plug the scanner into the port, it powers up the scanner and gives me the turn on key prompt. When I turn on the key, it responds and starts the connection protocols. I would think that the initial power up confirms my battery power and grounds, and the response when the key is turned on should confirm that it is getting a signal from the ECU. Any ideas why it wouldn’t link?
Could I have the wrong pin out from the ECU? Bad ECU? Too long a data wire between the ECU and the port? I’m floundering here! Help!
Start with confirmation that the scanner works successfully on another car(s).
I had that problem with my HF scanner. The 9V battery was weak.
Unfortunately it does work on my gm truck!
There are two powerups at the DLC, no? Constant power and switched ignition?
If you used GM wiring then any solid orange wire is constant +ve and any solid pink wire is hot only in start and run.
You should be able to check for voltage on the data bus wires. IIRC they have a constant 2.5v (fuzzy here: I have books to remember the details for me) and one is a square wave to ground and the other is a square wave to 5v, mirroring each other. You won't be able to see the pattern with a voltmeter but if you have a nice digital meter you can at least verify the presence of "something" on the DC scale, which would tell you that there is connection to the PCM. If you have another GM at your disposal you can run the meter on it to get an idea of what nominal is.
Also there are two ground leads at the DLC but (again IIRC) one is sensor ground and the other is PCM ground, as a diagnostic function.
Oh yeah... apologies if this is old news to you, but never check a female terminal by shoving a test lead in it. That will bend the contact and ruin it, so it won't make a connection anymore when plugged in. Always backprobe the connector, or make contact to the side of the terminal.
In reply to Knurled. :
Thanks for the info and the heads up!
I will see if I can detect the signal with my volt meter. I was assuming that since it changes the screen in the scanner when I turn on the ignition, that, that showed there was a current / signal coming from the computer. Wouldn’t that be the case?
Just checking, what is DLC?
if that is what I’m calling the “port”,it only has 4 wires. 2 grounds, a constant power and the data wire.
I was assuming that any switched power was coming through the computer via the data wire when it powers up with the ignition.
In reply to Sofa King :
I'm a technical weenie. That 16 pin connector with the trapezoidal-ish shape that you plug a scan tool into? That's the Data Link Connector, or "DLC".
That funny orange light on the dash that looks like clipart of a 1970s engine is also the "Malfunction Indicator Lamp" 
You may be right, there may only be one data wire on a vehicle that old.
Alright just because I wasn’t sure what DTC stood for doesn’t mean that I don’t understand cartoon engines! That must be a MIL! Damn I’m catching on!
Assuming that there is only one data wire, does that mean that when it responds to the ignition switch, I’m getting a signal from the ECU! (Haha! See what I did there?!)
No, when it responds to the ignition switch, it means the switched line came on, not the data line. How old is the 9V battery? I'm telling ya, I had the same problem. It even talked to some cars but not others. Then there's the BIMIAMUTI.
I’ll try a new nine volt it’s way easier than my other options!
BIMIAMUTI? OK, now your just messing with me!
Yeah, But Ignore Me I AM Used To It. It's a Hip Kid Thing. y0.
Shows how far out of it I am!
Dr. Hess you glorious bastard it worked!!! Thanks for being so persisted with the new battery suggestion! I was 100% positive my battery was good... I was 100% wrong!!!
