Hello All,
I did a lot of searching but could not find this exact scenario and I was wondering if anyone on here has had something similar happen to them (before I fry another ECM).

I have a 2009 SS, Automatic that just died one day (204K+ miles). The MIL was flashing super-fast, probably 10~15 flashes per second. My Autel couldn't connect to the car. A quick check and I found the 20A ECM fuse smoked (#41 in the under-hood fuse box). I knew the issue wasn't a defective fuse, but I went ahead and replaced it to see what would happen. Everything seemed to power up correct, but it would only crank over but not start. After that attempt to start, the 20A ECM fuse was smoked again (surprise!).

I put a new fuse in to see if I could at least get my Autel to connect and it did. I was able to pull P0689 from the ECM (other modules' codes seemed to be related to communication errors with the ECM and didn't matter). Opened the service manual, and that led me down the path of diagnosing the powertrain control relay (P0689 is zero voltage at the ECM, when it expected B+). Everything checked out fine, so I checked some other items and discovered that the leg of the ECM fuse that leads to pin 3 of the X2 ECM Connector was shorted to ground. If I disconnected the X2 connector from the ECM, the direct short went away, telling me the ECM was smoked (for grins, I did check the circuit for no resistance and short to ground or B+).

I happen to have other Automatic SS cars, so I performed the same check and with the X2 connector connected to the ECM, there was some connection to ground, but real jumpy, and in the megaohm range. So, I pulled the ECM and put it in my dead SS (risky, I know) and everything powered up correctly and no more defective fuses... Of course, the car wouldn't crank, because the security system didn't match the ECM, but everything was acting normal.

I ordered a new ECM that will be programmed to my VIN from Flagship One in New York. It is refurbished, but I didn't have to supply a core, and it is only $365, shipped.

I DO NOT plan on installing my new ECM until I have had a chance to pull the entire Engine harness and inspecting for chaffed corrugation or wires. But, back to my original reason for the post, just wondering if anyone else has run across this scenario and if it in fact was "just a bad ECM"? I've had very little reliability issues with Bosch components in vehicles, so I am leery of it being just a bad ECM, but after 204K+ miles, I suppose something is bound to give out.

Any and all input / comments are appreciated.

Sincerely,
Robert

 

I was cleaning up my tools and for grins, gave the smoked ECM the sniff test. It definitely has the smell of burned electrical components, whereas the other one does not...

 

When you have a fuse blow like this we load test the circuit to be sure the wiring is not the issue. I would use an led bulb as load and test it while you are waiting for the PCM. You may find it's not the module at all.

 

Thanks for the reply Greg. I'm assuming you mean put a load on the B+ side of the ECM fuse? That's easy enough to check. Thanks again!

 

The thing is there may be other things that blow that fuse. The connector itself could be the problem. If they crack they can cross inside the connector. Also, I've seen problems with devices the PCM controls that are shorted and will blow the fuse. The most common is a coil.

 

Running through the P0689 diagnostic ruled out the power control relay being the issue and since everything acted "normal" with the different ECM (save the cranking because of the security issue), I have to assume the ECM is the fix, I just want to cover all bases before I replace the ECM.

 

Something you could do is put a fuse in and with the PCM disconnected and then key on wiggle on all the wiring you can and see if it blows again.

 

Why do you think the no crank is caused by security issues?

 

He installed an ECM from one of his other SS’s so the VIN isn’t recognized

 

Yep, and the security light on the dash was on solid.