Need Help with OBDII wiring

[VRaptor SpeedWorks, LLC]

I will post some pics below. I'm working on a customer's GTM that is using the donor C5 engine harness, underhood fuse box and painless wiring harness. I'm running into a problem with getting any connection to the ECU thru the OBDII. I've tried connecting via my laptop and HP Tuners and my bluetooth OBDII dongle and neither will connect to the ECU. After doing some investigating, I see that the green wire in the OBDII connector is not hooked up to anything. The purple wire appears to be hooked to something, but I can't tell what as it is taped into the main harness under the dash and I'd have to tear the whole thing apart to see what that purple wire is hooked to and where it goes. The FFR assy manual doesn't appear to mention hooking up that purple wire at all. The black and the black/white wires in the OBDII connector are grounded to the chassis like they should be according to the assy manual. The orange wire is connected to power as it shows in the manual. After lots of digging, it appears that the green wire should come from Pin M in the C150 connector. That connector is gone on this car.....there are not 3 different round connectors in the donor harness like there should be....only one.....and the colors of the wires in that round connector don't match up with any of the pin-outs in the 1999 service manual I have here....and the donor is supposed to be a 1999 donor.....so I can only guess that the owner got rid of the other 2 round connectors by pulling all of the pins and combining all 3 of those round connectors into one connector? At any rate, further digging indicates that the M pin wire that is supposed to be hooked to the green OBDII wire comes from Pin 58 in C1 of the ECU connector. So I ran a wire that connects directly from Pin 58 to the green wire of the OBDII. Still nothing....can't connect to the ECU. According to the service manual, the green wire of the OBDII/Pin 58 and the purple wire in the OBDII are all connected together thru "Star Connector 1" in the photo below. After connecting Pin 58 to the green OBDII wire, I ohmed across the purple and green wires and there is no connection there.......and again....it does appear that the purple wire is connected to something as it disappears into the main wire loom under the dash, but I have no idea where it goes to. Any suggestions?

[VRaptor SpeedWorks, LLC]

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[VRaptor SpeedWorks, LLC]

I should also mention that in trying to hook up his AC, I was going to wire that into the ECU so that the ECU controls the AC clutch, cooling fans and idle speed......but none of those wires exist in the ECU connectors. In the pin location for the "AC Request", the 3 pressure sensor pin locations, the AC clutch "confirm".....there are no pins or wires in any of those locations in the ECU connectors.....and going down the pinout in the 1999 service manual, only a few of the wire colors in the ECU connectors match what they should be. So not sure if the engine harness is from a different year or exactly what is going on here.

[VRaptor SpeedWorks, LLC]

Here is some more of what I'm talking about. This photo is the C1 Blue connector on the ECU. Look at the wire colors compared to the pinout in the service manual.


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[VRaptor SpeedWorks, LLC]

Pin 61 is orange. Service manual says it should be PNK/BLK
Pin 62 is green. Should be GRY
Pin 63 empty. Should be BLK oil press sensor ground
Pin 64 is gray. Should be N/U
Pin 65 is empty. Should be PPL O2 sensor signal

Etc, etc.....

Owner says car starts but won't stay running....so if it starts, obviously the ECU works and the engine harness is the correct one for this ECU? He was thinking this was part of the VATS problem, which is why I'm trying to connect HP Tuners to check. I did figure out today that his ignition switch was wired wrong....so that the ign power was tied to the start wire....so IGN+ only had power while cranking, which would explain why it would only run while cranking, but still wanted to check the ECU since this car has had ALL of the wiring faults that all of the early cars did due to mistakes in the assy manual.....hazard circuit not wired properly, no ground wire for the cooling fans, ign switch wired wrong.....so I assume that the steering column lock issue in the ECU also has the same issue, which is why I'd like to get that taken care of right now in HP Tuners...

[crash]

No help here, but I HATE ELECTRICAL ISSUES! and feel your pain.

I VERY CAREFULLY, after making 4 pages of hand written notes and diagrams, recently had to redo a good amount of the GTM wiring harness on the FFR PDG GTM and it was not any kind of what I would call fun. I ended up with ONE WIRE that did not do what it was supposed to do. Had myself and another guy look at it and try and trace it to no avail. Very close to ripping into the entire harness but really REALLY don't want to do that because I am pretty confident where that will lead and I don't have that kind of time and money right now.

I was going to say that if the previous person eliminated plugs and combined things and it generally appears to work that he/she must have been pretty savvy, but then you mentioned the starter switch issue...

I hope your customer is paying you well.

Good luck.

[VRaptor SpeedWorks, LLC]

Wow....this thing is really testing me today....."one of those days". So, today I have fixed the issue with the Ign wire and Starter wire hooked together at the key switch. I turn on the ign and finally hear a relay click in the engine bay fuse box....yay!...we have ign power to the fuse box! Last week, I had to pull the pass fuel tank so I could remove the tunnel alum at the AC compressor because the AC clutch was about 1/16" away from the alum guard that covers the pulley and he had not plugged in the AC compressor....and the frame wasn't notched to clear the connector.....so I got all of the old fuel out of the tank while it was out of the car and all of that done and put everything back together and figured I might as well put some fresh fuel in the tank at this point and see if it will start....even for a little bit if the VATS is actually a problem. So for the first time since I've had the car in here, I crank the engine over....no start. Ok....hook up fuel pressure gauge....no fuel pressure. Oh....you stupid idiot...I always keep the fuel pump unplugged so that don't ever run the fuel pump with no fuel in the tank and ruin the pump. Oh...I have the test light right here already hooked up, I might as well see if the fuel pump is wired right. Stick the test light on pin A and turn the key on and the test light lights up!...yay!.....but wait.....the light just stays on? Why? I should only stay on for 2 seconds? Ok....the fuel pump is wired straight to Ign power. I look in the service manual that I already have open and see that the wire that powers the fuel pump from the relay in the fuse box is A12 in the C3 connector. I shine my trusty flashlight under there and what do you know?!?!....heavy gray wire just hanging there out of A12! Sweet!....cut the fuel pump wire from Ign+ and move it over to A12. Fuel in tank....hook connector to tank...turn on key. Nothing. What? Unplug fuel pump....test light to pump wire...turn key on with one hand with finger on the FP relay in the fuse box....relay kicks on and after 2 seconds, I feel it and hear it release. Test light to pump wire....turn key...still no power? Pick up lid to fuse box and track down the FP fuse. Fuse #13. Look in fuse box. No fuse in slot 13. Sweet!!....dig a new fuse out of the cabinet and insert fuse. Test light...turn key....have power for 2 seconds and then off! Yay!! Plug fuel pump connector back in. Turn key on. Nothing. No sound from fuel pump. What? Try cranking...still no fuel pressure on the gauge. What? WTF is happening here? Do I have ground for the pump? Unplug pump....ohm meter says yes on the ground to pin D. Plug fuel pump back in...key on...nothing. What?! Ok....go over to some old donor harnesses hanging on the wall. Holy ****....the first connector I grab is a fuel pump connector...Sweet! Cut the connector off the harness, plug connector into fuel pump....drag a car battery over to the fuel tank and use jumper wires to connect pin A and Pin D to the battery.....definitely have something in there pulling power as I get sparks when hooking up the wires.....and you can hear a faint clicking from inside the tank, but no fuel pump running. These are alum fuel tanks.....no way to drain the fuel I just put in out of the pump tank without it running all over the floor. F##k. Ok, I'll siphon it out. With what? I had the rubber fuel filler necks all hooked up and oriented the way I wanted......remove filler neck and use flashlight to shine inside of tank. First thing I see is that the float for the fuel sender is stuck all the way up against the side of the tank. That should be fun. Back to getting the fuel out so I can pull the tank back out.....all of the rubber hose I have around is all in a coil.....no way to keep it straight so it will go all the way to the bottom of the tank and stay there. Ok...I have a coil of 5/16 hard line here......uncoil it, mark it from the bottom of tank to the fill neck....dig out tubing bender....bend tube on mark.....kinks the tube right over. WTF? User error....was using the 3/8" slot to try to bend 5/16. Cut off kinked portion and start over. got tubing all bent so that one end rests on the bottom of the tank and the other end rests almost on the floor. get my 5gal gas jug fished over the end of the hardline...this should work! Now, how am I going to get the siphon started? Hmmm....lets take a plastic bag and wrap it around and over the hard line and zip tie it to the filler neck flange to seal up the opening in the tank. Drag the air hose over to the driver's side shove the air gun into the rubber filler neck and fold the rubber up so it seals against the air gun.....blow air into tank for a few seconds.....go over and check.....yes!!! the fuel is siphoning out!

.....to be continued tomorrow.....

[beeman]

Sorry to hear about your troubles.
I pity anyone who takes over someone else's projects, especially wiring.
As far as the OBD port, here's the wiring diagram and connector pinout, I'm sure you probably already have them though. You probably made sure the TWO grounds are adequate, and I would ground them to 2 separate locations like the factory did.
The positive is hot at all times.
I've heard of C5 obd connectors losing good pin connectivity to the pins on the diagnostic tool too, I'd consider switching out the OBD port to a new one as a last resort.

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[beeman]

Here's what I think you need, but probably not the instrument cluster, so purple right to the pcm.
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[beeman]

Michigan Motorsports OBDII OBD2 Wiring Harness Connector Pigtail Harness LS1 LT1 data link Camaro Firebird Silverado LM7 LR4 LQ4 LS6 L59 LQ9 LM4 L33 LS2 LH6 L92 L76 LY5 LY6 LC9 LMG LS3 L94 L99 WP0BD30 https://a.co/d/fw8bU3S

[VRaptor SpeedWorks, LLC]

So you're thinking that I should leave the DK GRN wire in the OBDII open/disconnected and instead connect ECU pin 58 to the PPL wire in the OBDII?.....or hook both the DK GRN and PPL wire to pin 58?

[beeman]

Here's mine, works and already have a base tune. Green not used, ppl to pcm. 174418

[VRaptor SpeedWorks, LLC]

I'll give it a shot!! Thanks!

[VRaptor SpeedWorks, LLC]

That worked!....I disconnected the DK GRN wire at the OBDII connector and connected pin 58 from the ECU to the PPL wire in the OBDII and got HP Tuners to connect and read the ECU! Thanks!

[Shoeless]

Holy smokes, what an ordeal.

Glad beeman was able give some insight.

[VRaptor SpeedWorks, LLC]

Absolutely! It's great to have guys like Beeman and you and a forum like this for all of us to use to our advantage!! I did try to track down what he had the PPL wire connected to, but failed. It disappears into the loom headed toward the rear of the car....soldered to an identical PPL wire and the only PPL wire I see of that same gauge back at the ECU/fusebox/round connector was in that lone round connector. I ohmed between the PPL wire at the OBDII and the PPL wire in the round connector and got nothing....so apparently that's not it.....so still have no idea what that PPL wire used to be hooked to.