Car won't start, U0100, Bad ECM?!

[Gunn]

Originally Posted by Seth21

Hi I am Seth and I am new here forgive that, I have a extra core ECM that I am not using but you will still have to flash it with GM Software.

Thanks for your generous offer and suggestions! Let me do a little more diagnosis...I've come up with a couple of more ideas and I'll let you all know how it goes. Then we'll go from there and I may be reaching out!

Tom

[Seth21]

Originally Posted by Gunn

Thanks for your generous offer and suggestions! Let me do a little more diagnosis...I've come up with a couple of more ideas and I'll let you all know how it goes. Then we'll go from there and I may be reaching out!

Tom

Tom stop guessing and remove the ECM and it may seem funny but if its burnt you will know fast. The fuses and all are being shorted by it.

Seth

[Gunn]

Originally Posted by Seth21

Tom stop guessing and remove the ECM and it may seem funny but if its burnt you will know fast. The fuses and all are being shorted by it.

Seth

Tonight I did indeed remove the ECM. Talk about easy, took about 20 seconds. When I smell the terminals, it's not a pleasant smell but it isn't bad. I have to hold my nose pretty close to the terminals. And it does smell somewhat like burned electrical. But I would have expected to smell worse from what you say. But then again, it probably shouldn't smell that way at all. So maybe that is a positive clue to a bad ECM.

I've done some research and I'm going to wire up a little harness with some spade terminals I have that will fit. 3 positive wires to the +12V terminals (with a fuse) and 3 ground wires to the ground terminals. Power it up and see if it blows the fuse. If it blows, it's 100% the ECM. At this point, I hope it is.

[Seth21]

Originally Posted by Gunn

Tonight I did indeed remove the ECM. Talk about easy, took about 20 seconds. When I smell the terminals, it's not a pleasant smell but it isn't bad. I have to hold my nose pretty close to the terminals. And it does smell somewhat like burned electrical. But I would have expected to smell worse from what you say. But then again, it probably shouldn't smell that way at all. So maybe that is a positive clue to a bad ECM.

I've done some research and I'm going to wire up a little harness with some spade terminals I have that will fit. 3 positive wires to the +12V terminals (with a fuse) and 3 ground wires to the ground terminals. Power it up and see if it blows the fuse. If it blows, it's 100% the ECM. At this point, I hope it is.

Hi Tom
I am glad you realized that the ECM is EZ to remove. I want you to perform a another type of test for me before proceeding any further ok? Remove the ECM entirely and place it on the passenger side floor board carpet to keep it safe No worries it is self contained and hold no risk of shock or static worries.

Next I want you to see if you have the Master Key Original handy. If not this may not work. I want you to remember how much Gas you had in the tank before this mess started. With that in mind and with battery installed and ecm out Please insert the key and see if the gas reads what it should have. If it does great! Then with the key dongle I want you to proceed with a Auto Start sequence. Yea I know it wont work with ECM removed but I am trying to see the status of BCM so watch the dash lights and interior lights during the test. If the BCM is bad those light will go crazy for about 3 seconds. If it still good test the logic on the radio please and tell me if it remembers your cell wifi and or your favorite channels please. please do this with key on! If the BCM is still data ready and viable all these should still be there. Then give the dongle a standard test, with drivers side window open and door's closed I want you to see if all other functions still work. This data is stored in the BCM for this. If all appears normal Great the BCM is still good and not suspect. If any of these fail try it with the same test with ECM installed. Please advise upon completion . Total time is 5-7 minutes to accomplish this no biggie.

Now take your Probe light (fuse tester probe) Attach the clip to adjacent fender bolts area for a good ground ok and with ECM OUT and key on I want you to start testing relays only for now. Two of them the larger Black ones are also used to regulate and direct DC Current to other circuits. Concentrate on the K series Start with K26 and work your way up ending in K632. I know if fuses are blow how can I check relays? We will isolate the bad circuit by this and see if the J class fuses are also bad and wich ones. most common is the ecm fuse has popped already and is bad. With the fuse replaced should be a 15 amp fuse located in the 20 area. Please consult your fuse Box cover inside for diagram of all. Yes I know all of this is common but it needs to be done first The ecm fuse should stay good as long as the ecm is removed. If you doubt your tester is working good then at the 12 v source wire touch it and test your probe. If it does not light up, check the ground again and use a body ground not the hood hydro shocks ok .

I will check your status after work tomorrow.
Gotta Bounce for now

Seth

[Gunn]

FINALLY, Progress!!

Fist, Seth thanks for the info. I did go out and test the BCM as you mentioned. Everything was fine that I could think to test, except the fuel gauge showed empty (I know there is about 5/8 of a tank remaining). But this was an original symptom of the blown fuse (and therefore no power to the ECM). The fuel gauge must be powered by something from the ECM, never did dive into that further.

Ok, the moment I've been waiting for. As I mentioned previously I removed the ECM and took it to the workbench. I created a small power wiring harness with three wires to apply +12V power to the power pins (3, 5, 6) and three wires to apply ground to the ground pins (1, 2, 4) in the X2 ECM connector. Small crimp spade terminals that I had to pry open just a bit worked perfectly on the ECM terminals.

I added an inline fuse holder and a 15A fuse. Sure enough the second I touched the positive wire to the red terminal of the 12V battery, I heard a faint click in the ECM and then the fuse promptly blew! I tried it again for good measure; same result.

So now I have definitively proven the ECM is responsible for the short-to-ground within it. I had already proven the wiring harness for these 3 positive PNK/BLK wires from the load side of the fuse to the ECM pins was good with no shorts.

I have the ECM boxed up and ready to ship today to Module Experts. They'll do a lifetime warranty repair with a three business day turnaround. With my shipping cost to them included, it's just a bit under $200 total.

I'm sure I'll still be anxiety-ridden when I plug it back into the car, but I feel pretty confident I've found the problem...one of the lucky (unlucky?) ones with an actual ECM problem! Trust the wiring diagram. It showed me the complete circuit I was dealing with.

Thanks everyone for the tips, help and suggestions, I'll update as soon as I get the ECM back and see what happens.

Tom

(And in the pic below, the 3 ground wires are indeed mostly black, though it doesn't appear to look that way in this photo! They were a red/black wire combo that I separated).

[fz4k98]

Sorry to hear all u are going through but man this is some amazing problem solving u are doing.

[Gunn]

Originally Posted by fz4k98

Sorry to hear all u are going through but man this is some amazing problem solving u are doing.

Thanks! Appreciate the kind words, keeps me motivated when I pretty much want to crack open a beer, set the car on fire, sit back and watch.

I sent the unit into Module Experts. They confirmed my diagnosis which was fantastic, but also met with some unfortunate news:

Our technicians have informed me that diagnostics are completed on the Camaro module, and this unit is beyond repair due to the issue being traced to the main processor (computer chip). The chip is not able to be replaced on this module, as it is made into the circuit board assembly, so you would need to replace the unit to correct the issue. There is nothing that can be done to save this unit. It must be replaced.

So now instead of getting out from under this at under $200, my price just about doubled. Still much better than taking it to a dealer, so feel good there.

Just ordered one from Flagship One for $369 and hopefully will receive it early next week.

I'll let you know how it goes!

Tom

[gtstorey]

The one time I ordered from flagship one took forever to receive it. I basically had to threaten to cancel the order before they shipped it. It was a fairy rare ECM so hopefully yours will be quicker.

Mine did work as it was supposed to once I got it.

[PaulsSS]

So a new ecm solved the no start?

[Infidel67]

Originally Posted by Skelly

Hi I have a 2011 SS and the system is doing funny things and I am wondering if anyone has experience with these issues? I replaced the ECM two years ago and it came with non gm software loaded. It ran only after we called a locksmith to Re Auth the keys. 8,000 miles later we are back to random no starts and gas gage not functioning correctly. Thanks

Sean

You might want to start your own Thread on here

[Infidel67]

https://www.camaro5.com/forums/newth...=newthread&f=2

[Skelly]

Originally Posted by Infidel67

https://www.camaro5.com/forums/newth...=newthread&f=2

Thanks figured it out, Nice car! I think I will trade mine in on a subaru :(


Sean

[Infidel67]

Originally Posted by Skelly

Thanks figured it out, Nice car! I think I will trade mine in on a subaru :(


Sean

Nahhh don't do it Bro

[wickden]

Originally Posted by Gunn

Tonight I did indeed remove the ECM. Talk about easy, took about 20 seconds. When I smell the terminals, it's not a pleasant smell but it isn't bad. I have to hold my nose pretty close to the terminals. And it does smell somewhat like burned electrical. But I would have expected to smell worse from what you say. But then again, it probably shouldn't smell that way at all. So maybe that is a positive clue to a bad ECM.

I've done some research and I'm going to wire up a little harness with some spade terminals I have that will fit. 3 positive wires to the +12V terminals (with a fuse) and 3 ground wires to the ground terminals. Power it up and see if it blows the fuse. If it blows, it's 100% the ECM. At this point, I hope it is.

It's great that you took the initiative to remove the ECM and investigate further. Wiring up a harness for a controlled power test is a practical approach to troubleshoot the issue. If the fuse blows during the test, it will indeed provide a clearer indication that the ECM might be the culprit. Your methodical approach to diagnostics is commendable. Best of luck with the test, and I hope you find a resolution to the issue. If the ECM turns out to be the problem, at least you'll have a more defined direction for addressing the problem.