2014 Chevy Sonic Sedan LT (1.8L) showing U0100 after swapping out Climate Control Panel and Transmission Shift Assembly

[mikami]

I have a 2014 Chevy Sonic Sedan LT (1.8L). My Climate Control Panel and Transmission Shift Assembly quite worn so last I replaced them last night with newer, but used, pieces. I removed the center console and replaced the items fairly easily. After plugging every thing back in I found that the car power would come on when I turn the key but the engine wouldn’t turn over. I thought maybe I didn’t have all of the plugs in all the way so I redid the plugs and pushed them in hard. That didn’t work.

I checked the codes and the only code that shows up is U0100 (communication has been lost between the ECM/PCM (main computer) and a particular control module).

The only think I can think of that I did to cause this is, I didn’t disconnect the battery before I did this. I completely realize this was not smart and I may have got what I asked for. I honestly thought I was just disconnecting / reconnecting cables so didn’t think anything bad could come from that. My bad!

Next, I tried the following. None of it made a difference:

• Put the old part parts back in. All of the knobs/lights seem to work. The shifter also works when I turn the key. It just doesn't start/turn over.
• Unplugged the battery for 30 minutes and plugged it back in.
• Checked all the fuses in both the engine compartment and below the steering wheel

Since it wouldn’t start I even had a mechanic come by the house today. After charging me he said he couldn’t do anything about it and would likely have to have someone come replace my ECM with a new ECM.

Does anyone have any other thoughts as to what I may have done or do you agree with the mechanic that I may have burned up my ECM?

Attached is a pic of what my dash lights look like after trying to start the car and when the initial lights go away. I see the traction control and power steering alerts on. I also see that the current shift position is missing from the display.

Thanks for any thoughts.

 

[mikami]

Just an update...I checked every single fuse and swapped the "Start" and "Run/Crank" relays. That didn't help.

I have an ECM on the way from Flagship that will be programmed to my VIN. I'll let you know how that goes.

 

[mikami]

For a final update. This did end up being the ECM. The downside is I purchased the ECM from Flagship One then, it still wouldn't turn over. I tried several things over a few week period.

I ended up towing it to a Chevy dealer who said the "new" ECM wasn't working. They tried to program both it and the original one. Neither one worked so I had to pay them for a new ECM + programming.

The good news is the car now starts.

The bad news is I'm out 2 ECMs + Programming. Per Flagship One's website:
"All returns for money back must be received by Seller within 30 days from the date of original purchase."

That didn't happen because of trying different things to get it to work and the holidays. I'm still going to give it a shot though to see what they say.