Not an actual corgi's Build Log - 2007 SS/SC

[Corgithulhu]

I appreciate the thought process, it helps start down new paths to fix it. You might be on to something. I didn't make any harness modifications, except for running the CHMSL wire to both rear stop lights after building and starting the car, since the normal stop light plugs weren't lighting up. Ever since I got the car running, I've had an issue that I can't track down where the tail lights stay on dull unless battery power is cut. There might be some back feed interfering like you said.

I did have the battery deep cycle tested, and it passed. But when I looked at it, it was clearly a used battery and not the right model for a Cobalt, so I just got a new battery for the peace of mind. Should have done it when I built the car, but I was excited to get it going. Glad that's done now.

 

[Desert Sasqwatch]

Best way to troubleshoot an electrical gremlin is to divide up the circuit. Start by disconnecting - if possible - parts of the circuit, head lights, tails light, 3rd brake light, and see if that makes any difference while you are doing the connector checks and harness wiggle-jiggling. Keep us informed of any progress.

 

[Scott #321]

Best way to troubleshoot an electrical gremlin is to divide up the circuit. Start by disconnecting - if possible - parts of the circuit, head lights, tails light, 3rd brake light, and see if that makes any difference while you are doing the connector checks and harness wiggle-jiggling. Keep us informed of any progress.

50/50-90 rule comes into play on this. Divide the circuit in half and you have a 50/50 chance on which side the problem is on. You have a 90% chance of starting your diagnostics on the wrong half of the circuit.

 

[Rttoys]

I did have the battery deep cycle tested, and it passed. But when I looked at it, it was clearly a used battery and not the right model for a Cobalt, so I just got a new battery for the peace of mind. Should have done it when I built the car, but I was excited to get it going. Glad that's done now.

good. I hate battery issues. I have a rule that anything over 2 years old is subject to problems. it’s $100-150 to give you peace of mind.

 

[Corgithulhu]

Well, update: I came out to the garage this morning and I had left the battery switched on by mistake. For some reason, the hazards were flashing dimly, I guess from that being one of the buttons we tried manipulating when it was dead at the gas station. I turned the ignition to run and hit the flashers, and they turned on normally, but wouldn't turn off fully with the key off. But the dashboard gauges did come back with key on. Switched the battery off and everything died as expected.

I checked the BCM2 and 3 fuses under the hood fuse box, and they were good. I think BCM3 just powers the switched leg of the HVAC relay, but worth checking I suppose. BCM2 is 40A, and I believe supplies power to the ignition circuit of the BCM.

The BCM 50A fuse near the battery was also intact, but the blades were a bit dingy. I recently had an issue on my Duramax, a 2007 MY like the Cobalt donor, where the glowplug fuses were similarly dingy, and cleaning those with a wire wheel solved the electrical issues I was having. With that in mind, I brushed off the 50A contacts and put it back in. Got my gauges and lights again, and no hazards flashing. Went to start it, and the security light on the dashboard lit up when the ignition went to start, and no starter spin action, just the clunk of the solenoid.

I had to run the GMLan green wire that's unique to the 2007 SC models on its own...I wonder if it got worn through somewhere and is shorting to the chassis.

 

[Gtstorey]

Some basic checks on the data wires can be found here.
SECTION ‘X’ CONTENTS (aeswave.com)

 

[Corgithulhu]

That's an awesome resource Gtstorey. I used it to check some things, and they looked good.

I tried starting again, and I got a really half-hearted crank past one cylinder's compression. So I checked battery voltage, and it was only 11.4. Must have been sitting on the shelf for a hot minute. Hooked it up to the charger, set it to yeehaw start mode, and it fired up. Maybe it was a janky old battery after all. It's currently on slow charge since it still wasn't perfectly full. I'll try doing a few A to A runs where I don't cut it off, and see if it allows starting after a few minutes of sitting in my driveway, just to test restart-ability.

Electronics are weird, man.

 

[Corgithulhu]

Welp, I am thinking I have made serious progress with this electrical issue. I took all the BCM and the under-hood plugs out, and sprayed them with Deoxit D5 per its instructions (short spray, actuate connector, short spray, let it sit a couple minutes). I also took the front and rear ground lugs apart and wire wheeled all the tabs, as well as hit the tabs' holes with a drill bit to deburr the holes, trying to get maximum contact. Put it all back together, and all the little gremlins seem to be gone! I no longer need to have the headlights on to start the car, and my taillights no longer flicker from low voltage...they also flash like they should!

I can't wait for it to stop working since I gloated about it to others.

 

[Corgithulhu]

Sitrep: it stopped working. Teaches me to gloat. Cold and dark when I tried starting in my garage on Sunday.

I did some poking around Sunday evening, and found the positive post on the fuse box was only seeing a couple volts. Since that should always equal battery positive, that definitely got me thinking. I was worried my solder work failed on the lug when I shortened the battery positive cable that runs to the starter. Turns out, whoever built my Goblin put the lock washer between the B+ tab theand other two tabs. Also, the alternator cable tab, starter-to-fuse cable tab, and nut/washer were also covered with 10 years of slight corrosion. Dremeled off the tabs to clean metal, and picked up a new M8 nut/lock washer.

I checked again before starting work today, and it was only a couple volts. After I cleaned up the corrosion and stacked the tabs/washer/nut correctly, it was full battery power. Started her up, full alternator voltage.

I will not gloat this time. Hopefully I exorcised another demon, and fingers are crossed.

 

[Corgithulhu]

Boy, it's been a while. So the situation with my power issue above has not occurred since. Chalk that one up to monkey brain during assembly of the starter/battery cables.

I finally got the DF billet shifter kit, and installed it a couple weeks ago. Fully worth the upgrade if you have the stock plastic shifter. The kit goes together nicely, the only curiosity that I didn't see mentioned anywhere (hopefully I just missed it) is that I had to swap the cables. All I had to do was pop the cables off the transmission linkage and swap their position. I reset the ball sockets on the transmission side at center neutral to "re-calibrate" them, and it's been off to the races since.

Shifting with this is night and day difference. You can feel the synchros and gear dogs engage, it's a very satisfying mechanical thunk. I had an issue where fifth and reverse were difficult to engage on my stock Cobalt shifter because the plastic mechanism was just worn out. Now I can confidently use fifth and reverse without slamming it around a bit. Highly recommended!

Side note: I recommend starting with the shortest throw first. It's not actually super short, but it's also not stock where you get very friendly with your passenger's thigh.

 

[Rauq]

How are you doing?

 

[Corgithulhu]

How are you doing?

Hey man! Doing very well, hope you are too! Just a busy year, especially getting married in October, so a lot of calories and money are going that way instead. Also, it's just been too hot and muggy around here to get out and enjoy buzzing around the Goblin! I've been waiting on the end of summer or just a drop in temps to get out again.

 

[Rauq]

Hey man! Doing very well, hope you are too! Just a busy year, especially getting married in October, so a lot of calories and money are going that way instead. Also, it's just been too hot and muggy around here to get out and enjoy buzzing around the Goblin! I've been waiting on the end of summer or just a drop in temps to get out again.

laaaaame, I drove my car to work Tuesday through Friday last week and yesterday and today as well! Congrats on the wedding!