V1 No Start, Was Working

[Gtstorey]

Did you ever jump any relays while things the fuse box was hot? The normal trace burnout is where people jump the fuel pump relay to pump fuel and cross directly to ground. I don't remember how many circuits the affected beyond the fuel pump relay.

Theoretically, the fuses should be sized to not damage the traces so make sure the fuses aren't oversized from stock.

 

[k.rollin]

Update: I think I have isolated this problem to the fuse box. I get battery voltage on x8(jump post), as well as all leads on x4 fuse block. Low voltage seems to be just the circuit for the PCM/ECM fuse (x5 block). Actually, there are other fuses in the surrounding area also with low voltage but they are unrelated to the ECM circuit (still concerning). So this seems to be a problem with the fuse box. I'm going to take the weekend to triple check everything to be certain before I order another. I still haven't visually inspected the PCB. I did connect to the ECM through GODIAG (I posted about that in a separate post) and was able to pull DTC, so it's for sure not the ECM itself. Some of the codes indicated previous low voltage warnings so that's definitely something. I'm on the right track I think.

I've got a spare fuse box from an 08 Cobalt LT automatic that I'd let go for a fair price if you're interested. I bought it when troubleshooting my cooling fan issue (before giving up and adding a standalone fan controller) and because I wanted a cover with the red cap for the positive post.

 

[glantz]

If this ends up being a burnt circuit trace on the PWB in the fusebox, the source of the problem needs to be located so a new fusebox or a trace repair doesn't result in a repeat. In most cases, a burnt trace is the result of that circuit being shorted to ground and pulling more current/amperage than the trace can handle. The connection to the fusebox and wiring associated with this circuit should be checked with an ohmmeter to look for shorts or very low resistance to the frame ground points.

When you have located the burnt trace on PWB inside the fuse box, it can be fixed if you have soldering skills. Cut the burnt trace out of the circuit and solder in an appropriate wire to bypass this bad circuit - 22 gauge wire if it's a narrow looking trace, 16 gauge if it's a thicker looking trace.

All very good information and advice! Much appreciated! I will go through all of it this weekend. I’m closing in on it I think.

 

[glantz]

Did you ever jump any relays while things the fuse box was hot? The normal trace burnout is where people jump the fuel pump relay to pump fuel and cross directly to ground. I don't remember how many circuits the affected beyond the fuel pump relay.

Theoretically, the fuses should be sized to not damage the traces so make sure the fuses aren't oversized from stock.

Yes I jumped a couple times. First the fuel pump while emptying tank from donor. Second time was the crank relay. Both were way before this issue began though I suppose it could have contributed.

I actually did find an oversized fuse just after this happened that, in the back of my mind, I suspect could be involved. I haven’t yet compared to diagrams (or inspected) to understand. It was labeled outlet, had a 25 instead of 20. Every other fuse checks out compared to lid diagram.

 

[Gtstorey]

You might have damaged the trace, but not burned it out completely and then it continued to degrade with more load being applied.

It won't surprise me if there are other issues besides this low voltage to ECM, especially since I think we started tracking this down because the ECM wouldn't communicate at the time. But this still needs to be fixed since it will likely cause a problem at some point even if it isn't the main problem.

 

[jennam]

Highway 160 Auto Recycling in Nixa shows they have an engine fuse box for a 2008 2.2L for $55 if the traces on your board are shot and you want to pick one up locally.

 

[glantz]

Highway 160 Auto Recycling in Nixa shows they have an engine fuse box for a 2008 2.2L for $55 if the traces on your board are shot and you want to pick one up locally.

Awesome! Thank you. That’s super close. I appreciate that!

 

[glantz]

Update: I can’t believe it!! I think I have it figured out! I was stumped today. No burnt traces on PCB and everything looked and tested fine. Spent hours going over everything. Frustrated, I came inside to take a break and then I started thinking there MUST be a common thread among these low voltages. All power is good coming into the fuse box. What could this be? I started thinking about grounds again as the only other possibility. I went back to the shop and started to physically trace grounds from the fuse blocks. All of the ones in question traced back to a lug that was grounded to transmission. Interesting. The lug was clean and tight and power probe tested good on ground. Then I recalled a few people here saying they had issues until they moved the lug to the frame. Figured what the heck? So this is exactly what I did. I cut the harness tape and rerouted the grounds to the rear frame ground. I turned the key and bam, it’s good! All fuses now read battery voltage and I can pull DTCs.

This was so obvious and basic that I’m almost embarrassed. I have checked and cleaned grounds at least a hundred times! It was the first thing I checked when this began! Can’t believe that was it! What threw me off so bad was that it was working and suddenly stopped. That part is still hard to explain. You would think it would have never worked. It’s working now though so I’ll take it!

I want to thank everyone here for the support! You all have been so helpful. THANK YOU!! I’m sure I’ll have more questions but hopefully not about wiring

 

[ctuinstra]

The engine has to properly ground to the frame as the frame is the primary ground. When you paint/powder coat the frame, the engine mounts don’t make a good ground.

You will want a ground cable from the engine/transmission to the frame also. Remember, your spark plugs need a good ground also.

 

[Gtstorey]

This is why I recommend tracing low voltage issues by running a wire directly to the negative terminal of the battery. Voltage good on the wire, bad on the grounding point leads to the grounding point not having a good connection.

 

[glantz]

This is why I recommend tracing low voltage issues by running a wire directly to the negative terminal of the battery. Voltage good on the wire, bad on the grounding point leads to the grounding point not having a good connection.

This is what I was doing using a power probe. It connects directly to positive and negative battery posts. It’s a handy tool but wasn’t really effective at helping find this issue. It was helpful in isolating low voltage but it signaled good ground when in fact it wasn’t fully grounded.

 

[Gtstorey]

Power probe that reads out a voltage or just a light?

 

[glantz]

Power probe that reads out a voltage or just a light?

Yes it displays voltage and just signals on ground.

 

[Esstover]

Looks like a good place to start my plea for help. I finally picked up a donor this weekend. It's a 2006 SS/SC. It's been sitting for awhile. It turns over but it is not firing. I've found some posts about wiring issues with the ground of the coil packs. From what i can tell from the diagram I have each coilpack has 4 wires. One of this is a black and that should go to ground. When I check continuity between that pin and ground I get nothing. I've tried to check every ground I can find and I can't seem to find where these wires are tied. One diagram I said showed G107. When I find a diagram that shows me the location of G107 I don't have a ground there. I think the problem is the diagram I am looking at is for an 2008.

So first question. Can anyone confirm that I am right and I should be able to check continuity between the pin with the black wire and the chassis?
If yes, then where can I find the other end? I'm not really ready to strip everything down. I'd like to get it running first.

 

[Gtstorey]

Yes it displays voltage and just signals on ground.

Did the voltage read 9 volts with the power probe?

 

[Gtstorey]

I only have the manual for the later models but I would bet black is ground on the earlier models, so yes on continuity to chassis. It doesn’t really matter where you ground it or where the other end is. Just go through the harness until all of the coil grounds are tied together and then splice in a new wire to a known good ground. Or just rewire from each coil to ground.

 

[glantz]

Did the voltage read 9 volts with the power probe?

Yes, it did until I moved the ground now it reads 12.

 

[Gtstorey]

Yes, it did until I moved the ground now it reads 12.

That strange. It read 12v on the jumper post and 9 on the individual wires? You might want to give your battery connections a good clean. Electricaly, same ground and same source should give you the same voltage.

 

[Ross]

Looks like a good place to start my plea for help. I finally picked up a donor this weekend. It's a 2006 SS/SC. It's been sitting for awhile. It turns over but it is not firing. I've found some posts about wiring issues with the ground of the coil packs. From what i can tell from the diagram I have each coilpack has 4 wires. One of this is a black and that should go to ground. When I check continuity between that pin and ground I get nothing. I've tried to check every ground I can find and I can't seem to find where these wires are tied. One diagram I said showed G107. When I find a diagram that shows me the location of G107 I don't have a ground there. I think the problem is the diagram I am looking at is for an 2008.

So first question. Can anyone confirm that I am right and I should be able to check continuity between the pin with the black wire and the chassis?
If yes, then where can I find the other end? I'm not really ready to strip everything down. I'd like to get it running first.

Perhaps a 2006 diagram would work better.

 

[glantz]

That strange. It read 12v on the jumper post and 9 on the individual wires? You might want to give your battery connections a good clean. Electricaly, same ground and same source should give you the same voltage.

I’m trying to understand this. Yes, it was reading 9v on one of the ECM wires as well as a couple other fuse receptacles. Every other fuse measured 12v. Battery post measured 12. Pretty much everywhere measured 12 except two or three fuses and their respective receptacles. My focus was on ECM so I really targeted that circuit.

I’m a true beginner with this stuff but what I thought was happening here, (or the way I understood it which could be completely wrong) was that with the power probe you were measuring voltage between positive lead to positive battery post. It would still rely on ground source it is using, right? So in my case it was partial ground and lower voltage. I moved the ground lug and it made full ground contact and thus the the wire now has full battery voltage. By comparison, if using a multimeter with positive probe on the wire and negative probe directly on the negative battery post, then I think it probably would have read 12v. That’s what I was thinking was happening here but I could be way off. Please correct me if I’m not understanding. Still learning