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V1 P2138 code and intermittent limp mode!

G
For the factory service manual you would have to make sure you are on the correct terminal since it calls out APP terminals A&D as low reference (ECM ground). The LSJ diagram posted diagram has terminals C&D as low ref. This is why it has to have the jumper connection. If you are just measuring resistance it doesn't matter as much.

I always prefer to use oem service manual diagnostic over random internet diagnostic. The other info may be correct but the OEM is more trustworthy to me.
 
C
It's still early, but I think new wires fixed my issue.

I pulled some 18/6 cable through the tunnel. It was far easier than I thought it would be. I keep thinking the tunnel is like 20 feet long, but it's only 6 maybe. Not a difficult pull at all.

Soldered wires into the PCM connector on the back end. Then cut my connector pigtail and used it for the pedal end. EZ PZ. The whole process took maybe 3 hours, and I drank a couple beers in the middle.

I have only driven it on two short trips, but no CEL so far. Power is good. Before the fix the light came on every ignition cycle. Two drives with no light is a victory for now.
 
Robinjo
Which connector is the C1 on the ECM? I'm having trouble finding which is 1, 2 and 3.....

I know it's this one, but I can't find which one one the ECM it connects to. I think it's the blue one?
39802
 
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C
You got it, it's the blue one. Conveniently it's the one on top, which makes access a little easier when you go to solder the wires in.
 
Robinjo
I did my cable last night. It took about 5 hours but I pulled the seats and tunnel cover (I have M4 bolts holding it in). Most of that time involved fighting with the drivers seat going back in. Next time it comes out I need to open to front 'jaws' that hold the seat into the frame better. Other than that it was uneventful until I went to fire the car. I couldn't start it and had 'Power Steering' on the dash. I reseated the connectors and fuse block (took it out originally thinking that was the C1) and it would finally turn over but still had the 'Reduced Power' message now. It finally turned over and had no throttle response. I had tried to rewire the setup to get rid of the jumper harness posted earlier. Took that setup back to stock configuration and NO 'Reduced Power' message along starting with no issue. I drove it this morning to something for about 10 and after for another 10 minutes, still no message. I'm going to give it a few days to say done but it's looking promising. Mine would go for a few days without giving me the error code, so still being on the cautious side before declaring victory.

Edit: 4 drives now with no issue. two 10-15 minute drive and two 20 minute drives.

I would say that since this has happened to at least 3 members here and countless posts on Cobalt SS for the same issue, new LSJ wirings for Goblins should consider just doing this from jump. With the harness out this would have been a 30 minute job.
 
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Robinjo
Well, my P2138 popped back up. I cut up my new jumper harness to try to get it out of the mix and had to revert back to the stock one. It is older and has thinner wires than the newer one I had. I reordered this. I also had reverted back to my old APP assembly as I thought it was giving better numbers. So, if the jumper harness doesn't work, then I'll put it back in. I thought about doing this anyways as it's less jerky with the newer pedal assembly. I turned back on all the P-codes that I had tried to band-aid fix my issue, so it should be popping up other P-codes for APP or TB if they were the culprit?

If those don't fix it, I'm open to ideas. That would have all the following done:
New APP
New Jumper harness
New wiring from APP to C1 connector on the ECM
New Throttle Body

Only thing not new in there would be:
APP connector on the main harness (I did check for continuity once I connected it all)
4' section of worse going into the C1 connector on the ECM (I didn't check continuity here after splicing in)
Wiring from the ECM to the Throttle Body
ECM
 
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G
Don't you have HPT? What voltage parameters will it track for the APP and ECT? You could also try and see if the ECM is grabbing any freeze frame data when the code is the code is thrown (with the right scanner) and see if that tells you anything.
 
C
Robinjo said:
Only thing not new in there would be:
APP connector on the main harness (I did check for continuity once I connected it all)
4' section of worse going into the C1 connector on the ECM (I didn't check continuity here after splicing in)
Wiring from the ECM to the Throttle Body
ECM
Click to expand...

I'm interested in that 4' section. Where did you splice in that you still have a 4' section of old wiring left?

I have about 2 inches of wire by the old connector on the APP, and about 2" of old wire by the C1 connector. I ran the new wire right up to the connectors as close as I could while still leaving enough to work with. So in total I have about 4 inches of old wiring, and the rest is 100% new.

Also, did you solder everything, or use butt splices? I'm not sure if it matters, but I used solder on mine and was very sure they were all good shiny silver connections when I was done. No cold joints here!
 
Joebob
I made sure that I also replaced the connector by buying a new one off Amazon, that way I had no more than 6" of old wires that lead into the C1 plug at the ECU. I also bought new APP and TB but neither of them fixed the situation prior to the new wiring. The resistance could be in the connector as well as the wires. I also soldered as a improvement over my original butt crimps.
 
Joebob
I would also check that you have good drag resistance within the wires in the C1 connector. I had a separate issue where a BCM plug was fully seated but I had individual loose female pins in the plug that did not reliably grab the pins on the BCM. A small paper clip was the right size to check the "drag" or grip of the female pin of the plug to determine the problem wires. Repinning a connector is no fun as the plastic is old and breaks easily but can be done.

Joe
 
G
Joebob said:
I would also check that you have good drag resistance within the wires in the C1 connector. I had a separate issue where a BCM plug was fully seated but I had individual loose female pins in the plug that did not reliably grab the pins on the BCM. A small paper clip was the right size to check the "drag" or grip of the female pin of the plug to determine the problem wires. Repinning a connector is no fun as the plastic is old and breaks easily but can be done.

Joe
Click to expand...
I de-pinned the unused wires from the BCM connectors. Bad mistake for the amount of good it did. I was about ready to cry by the time I got all of the remaining wires back in the correct position.
 
Robinjo
Gtstorey said:
Don't you have HPT? What voltage parameters will it track for the APP and ECT? You could also try and see if the ECM is grabbing any freeze frame data when the code is the code is thrown (with the right scanner) and see if that tells you anything.
Click to expand...

I do but do not know how to do all of that (yet). I know how to flash a tune and make very small changes to it. I've yet to jump into the data logging aspects of it. I haven't gotten into adding PIDs either.

Chubbs said:
I'm interested in that 4' section. Where did you splice in that you still have a 4' section of old wiring left?
I have about 2 inches of wire by the old connector on the APP, and about 2" of old wire by the C1 connector. I ran the new wire right up to the connectors as close as I could while still leaving enough to work with. So in total I have about 4 inches of old wiring, and the rest is 100% new.
Also, did you solder everything, or use butt splices? I'm not sure if it matters, but I used solder on mine and was very sure they were all good shiny silver connections when I was done. No cold joints here!
Click to expand...

I have roughly 2 inches of wire leading into the APP connector side and about 4-5 inches leading into the C1 connector. Both the APP connector and C1 connector are original Cobalt parts. I could order a new APP side connector but really do not want to mess with the C1. I used solder butt connectors to join everything. I made sure they seated and fully cooled before moving on to the next one.
 
Robinjo
So, a small development. I was messing with my cut up jumper plug that I tried to rewire the harness with to get rid of the APP jumper harness (while swapping the 18/6 cable) and the heat solder connectors that I used all pulled off with little force. There was no solder penetration into the other wires. This makes me suspect the whole setup may not be fully seated. I'm going to redo the setup with soldered joints and heat shrink tubing. I was going to reinstall my new APP assembly but I'm going to do one thig at a time right now. It'll eventually go in as it controls the second gear bucking (I do have a helper spring installed as well).
 
Rttoys
Helpful solder tip:

-connect your wires together
-Put wires on top of the soldering gun.
-Heat the wire and put the solder on top of the wires. Once the wire is hot it’ll melt the solder and it will work its way all through the threads. This will ensure a bond. If you just melt solder and lay it on top, you are not getting a bond, you are basically getting the same effect as tape.

See how the solder is through the wire, not on the wire
9DD912F9-0A65-444E-B5FA-C2FDFC7EC07E.jpeg
 
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