In the Summer of 2019 – I took my 2012 LS3 Vette out for a nice 90 miles ride. No issues. About two hours later when I started it up to come home – I got a check engine light. The car drove just fine, and I made it home without incident – I pulled the code and I believe it was a P6001 (PCM Memory Checksum error). The code would not clear. I drove the car a few more times and the Check Engine light continued to be on – but the car ran fine.

In Spring 2020 – I changed the car battery and the PCM. I got a new PCM, but I had it programmed by an aftermarket programmer – not a dealer (based on the VIN number). I installed the replacement PCM, and the car started up and ran fine. No check engine light. I did not use the car a lot in 2020, but I did notice that in the late summer – there was a definite “lag” between when I hit the start button and when the starter engaged (by lag – I mean something on the order of a couple of seconds). I noticed that a few times, but the car was running fine and there was no Check Engine Light. Then in the fall, I went to start the car up one morning, and it did not want to crank at all. I tried multiple times to start it, and it finally did crank and start (after a very long delay after hitting the start button – the cranking speed was normal – so it did not seem like a low battery or a fob communication issue), but when it started - most of the dash warning lights came on. I got “Service Active Handling System” and "Service Traction System" messages displayed on the DIC.. The car seemed to be locked in 4th gear, and was completely unresponsive to the paddle shifters, I drove it about a couple of miles and parked it. I pulled the code and got a U0100 Communication Error.

So - where would you suggest I start my troubleshooting ??? Would it be a good idea to replace the PCM again ??

 

I would start with battery cables/connections and grounds.

 

BUMP for other suggestions ...

 

It's common for a weak battery and/or poor connections to cause exactly these symptoms. The starter doesn't go slow because the ECU which controls it will have already passed out from voltage drop. So it either cranks and fires or does nothing.

 

OK - I put a top of the like Napa (Deka) AGM in the car last spring, but I will "test" the battery (I have a cheap conductance tester - that is actually pretty darn accurate as compared to a good old fashioned load test) - and I will go clean the battery connections thoroughly. Would you happen to know where the main battery to chassis ground connection is in the C6's ???

 

This Thread has some great Diagrams of all the Grounding points on the C6

https://www.corvetteforum.com/forums...locations.html

"If" memory serves me correctly it's #8 G104 in the diagram for the one coming of the battery - or you can follow the negative cable to locate it, but as you will see there are many more -

Thanks,Matt

 

Well tomorrow is supposed to be a nice day.

Sounds like a good day to go ground hunting....

 

With a “no crank no start” along with a “U” code I’d be looking at a possible communication issue...for this I’d be pulling out the scan tool to see what modules I can and can’t communicate with along with a scope and a CAN breakout box...since you are experiencing issues with the shifters that might lead me to a TCM issue...you can try disconnecting the TCM connector and see if the car starts if that is your main concern right now !!

 

Unfortunately - I did not get a chance to play with the car this afternoon (I hate it when work interferes with car stuff).

C5 Diag - Maddmatt - torquetube - THANK YOU for your input!

Unfortunately - while I do have a Chinese Knockoff Tech II, I do not have a CAN Breakout box, (and to be honest - I'm not all that good with the Tech II). My goal is to get the car running and driving like it should, and if the ground work does not resolve things - I will try to to Talk to the different modules with the Tech II, but I'm afraid at that point - I'll probably be seeking professional help. The problem there is to find a good place somewhere in the Northern NJ "area". (I already have a call into Doug at ECS - I've brought a C5 there for some work before).

 

Sounds goo - please keep your thread updated - it will help all in the future regardless of which direction you have to go -

Thanks,Matt

 

To bad you didn’t have this issue 6 months ago before I retired and moved down to Southwest Florida..I lived in Monmouth County. It’s a good idea to fill out your profile and put your hometown that way there may be someone on the Forum in your area that may be able to help. Early last year I helped someone who I found out lived only 3 blocks from me...LOL !!...with your Tech 2 after you get to the main menu you should see the screen which shows DIAGNOSTICS...select that and then I believe the next screen will show a screen that has VEHICLE CONTROL SYSTEMS in it...select that then you will see I think it’s MESSAGE MONITOR...select that and see if it shows the TCM...see if it says ACTIVE !!...I don’t know any good shops in Northern NJ !!...you have a pretty powerful tool in the Tech 2...you should learn how to use it by using it !!...usually with bus issues it will show “can’t communicate with the vehicle”.

 

C5 Diag - Again THANK YOU !!!! Will try this tomorrow.

I have a 2009 FSM, and I don't even see the U0100 code listed in there.

I have searched the forum - and I see I'm not the only one with this U0100 problem. However - most posts seem to be with earlier cars - and i see there was a factory service publication sent out about it - but that doesn't seem apply to the '12 cars.

 

Please listen to everyone's advice above as they probably know way more than me. BUT as a 26 year IT professional a memory check sum error to me sounds like a hardware problem in the ECU/ECM.

 

Orion2011 - I completely agree - that's why I changed the PCM in the first place - now I'm getting a communication error - not a memory checksum error... I just included the info about what happened in the past because it very well may be relevant to what I'm seeing right now....

 

So - I spent a little "quality time" with my C6 this afternoon.

I went right to the Tech II (before even checking a ground connection), and the good news is that it was able to "talk to" the car. I was able to communicate with the Powertrain Module, the Body Module, the Chassis module, and the Vehicle Control Systems module" (at least it appears that I was).

I asked it to give me PCM DTC's and it responded with "TCM Requested MIL Illumination".
When I went to the Trans Control Module - I got the error the U0100 "Lost Communication with the Engine Control Module".

I was not running the engine and when I asked for data - I did see 0 RPM, and a torque of -30 lb. So - I'm guessing that there is at least some communication going on with the TCM.

Based on what I saw - I would say I have a defective Transmission Control Module - or wiring harness on the trans. What do you guys think ???

 

GREAT !!...sounds like you’re making progress...if you can’t get any live data from the TCM the first thing before condemning the module are checking its power and grounds...maybe someone has the FSM wiring for your model year...you can check what you have and check wire colored of the connector...I will look also !!...good luck !!

 

So - Again - THANK YOU for your advice !!!

I saw screens on the Tech II today that I had never seen before....

BTW - in going over my notes from today I did find a P0700 code (Transmission Control Module). I will do some checking with respect to pin outs for power and ground - and I will try to jack it up tomorrow and do a little "inspection". (A quick look at online GM dealers show the module runs about $450 - $475 with a $100 core charge, and that it fits MANY MANY GM Models.).

A quick look on line shows that if I replace the TCM - it need to be programmed after being installed on the vehicle - correct?

 

Yes, a new TCM needs to be programmed !!

 

It sounds like you are able to communicate with the TCM, and the TCM is reporting that it couldn't talk to the ECM at some point. We could still be looking at a power problem. I'd like to see that ruled out first and the DTCs cleared.

 

Also keep in mind that the TCM is inside the gearbox.