V1 No Start Issue - B+ Terminal/Fuse Box

[Robinjo]

Nothing clicks or comes on. I’ll check the fuel pump for power just to verify but I do not think it has power. No lights on the dash either during the issue.
I do have power all the way to the B+ terminal on the fuse box. I do have power at the OBD2 port in spot 16. If I unplug the red BCM wire everything comes on. Also, if I remove the B+ terminal it’ll work after reconnecting the wire and bolting it down.
On the OBD2 port, I’m getting 60 ohms across the 6 to 14 spots on the OBD2 port. When I check the high data (6 to 16) I get 2.65 v and low (14 to 16) I get 2.35 v equaling 5 v. I haven’t unplugged the BCM or Fuse Box to see if the 60 ohms jumps to 120 ohms across 6 to 14, I plan to do that tomorrow.

 

[Gtstorey]

I don’t think those symptoms match a data wire problem.

check and see if the low beam headlights will come one. They aren’t routed through the BCM, at least on the newer models. They are a direct switch to relay to fuse to light to ground.

 

[Ross]

Have you tried backing off the 7mm bolts in the fusebox, then push the 7mm bolt to back off the electrical connector, then retighten the 7mm bolt to reseat the electrical connector. Do this to all the electrical connector blocks. Sometimes reseating them will fix intermittent electrical problems. You can do this on the rear fusebox, and the BCM.

 

[Robinjo]

check and see if the low beam headlights will come one.

No power at the headlights during the issue.

 

[Robinjo]

Have you tried backing off the 7mm bolts in the fusebox, then push the 7mm bolt to back off the electrical connector, then retighten the 7mm bolt to reseat the electrical connector. Do this to all the electrical connector blocks. Sometimes reseating them will fix intermittent electrical problems. You can do this on the rear fusebox, and the BCM.

I’ve done this a few times at the fuse box but not at the BCM yet. I’ll try that. I’ll also inspect all the connectors.

 

[Gtstorey]

No power at the headlights during the issue.

Check the diagram for your model and confirm but I don’t think your low beams do any different from the later models. You may have manipulate the multifunction stalk to get the low beams on though.

 

[Robinjo]

I’ll try that when I get home tonight.

 

[Gtstorey]

If they don't work at all, it may be a different problem. But if it doesn't work only when you have the no start issue, then it almost has to be fusebox related (again if your headlight circuit is the same as the newer models).

 

[Robinjo]

Along with checking the lights more thoroughly (working the stalk) I was going to do the last test from the video JoeBob posted. It involves taking the PCM out of the loop and checking the 6 to 14 ODB port Ohms and also with the BCM and Fusebox out of the If they go to 0 Ohms then there is an issue with that unit. It should go to 120 Ohms then that unit is ok.

 

[Gtstorey]

Fusebox isn't part of the data stream but the ECM is. But your 60ohm measurement from DLC pin 6-14 says the data path is ok.
I only sorta watched the video posted, but it might be not be completely correct. It will only read 120ohms if one of the 2 resistors that it uses is located in one of the modules you remove. I don't know where the resistors are in the early models, but the later models has one of the resistors in the power steering module, I don't remember where the second is. But knowing where the resistors are is important to interpret the results.

 

[Joebob]

Along with checking the lights more thoroughly (working the stalk) I was going to do the last test from the video JoeBob posted. It involves taking the PCM out of the loop and checking the 6 to 14 ODB port Ohms and also with the BCM and Fusebox out of the If they go to 0 Ohms then there is an issue with that unit. It should go to 120 Ohms then that unit is ok.

The 120 Ohms resistors are in the ECM and in the power steering computer and not in the BCM. That is a difference from the video.

Joe

 

[Robinjo]

The 120 Ohms resistors are in the ECM and in the power steering computer and not in the BCM. That is a difference from the video.

Joe

Well, then. I guess I can cut this testing out of the program. I do still need to take the BCM and Fuse Box out to inspect them though.

 

[Robinjo]

Even more curious, if you flip the lights from auto to on, the system comes to life.

 

[Gtstorey]

I would start with the headlight wiring diagram and track that all of the way through (on the car) and see if it tells you anything.

 

[Joebob]

The timing and that everything seems to work for a while and then stops makes me think that the BCM or something is timing out. Our cars in basic wiring form will hold the BCM awake for 15 minutes or so until it time out after we pull the key out. In Cobalt form, opening the door will force the radio, BCM, ect. to shut down more quickly. On mine, when the engine is off and key out but BCM awake, the gages read at zero. When the BCM shuts down, the gage needles flicker a bit and settle to below zero. Could it be that there was a miswire during extension or Body/Dash splicing, that is not letting the BCM stay active when the key is in the ignition? I know turning the lights on in mine causes relays in the BCM and Fusebox to click but have not had a need to diagnose which ones.

Awake

Asleep

Joe

 

[jirwin]

Even more curious, if you flip the lights from auto to on, the system comes to life.

Wtf this solves my issue too! No power anywhere but if I turn manual lights on it comes back to life!

 

[Joebob]

My mama used to say: "Once is an accident, twice is a tradition!" It seems we have a matching wiring mismatch. having consistency between two builds seems more like a miswire than a faulty connection. Look back over the later videos where you are building the dash wiring and adding all the grounds and building the headlight circuit like @Gtstorey stated.

Have a look through this to see pin outs to headlight and BCM functions and you might need to trace that the wires go to the right spot.

V1 - BAR-AIR's build up in Buffalo N.Y.

Yes those are 5 3/4” lenses. Just make sure they are the DOT lenses. Those were advertised as DOT lenses but when they showed up no DOT markings. Took about a month of back and forth with the manufacturer before they sent a set of DOT lenses. Nate’s car is using a set of 5 3/4” headlight shells...

dfkitcar.com

Joe

 

[Robinjo]

Wtf this solves my issue too! No power anywhere but if I turn manual lights on it comes back to life!

Did you happen to replace your light/turn signal switch? I did as my stock one was snapped in half.

 

[jirwin]

Did you happen to replace your light/turn signal switch? I did as my stock one was snapped in half.

As in the stalk? No, same one the car came with

 

[Robinjo]

Shucks, hoping it was a batch of defective units. Oh well, at least we have something to work down.