How do I access the ECM data on a 2005 Chevy Equinox? My wife was in a one car accident where the vehicle self accelerated into a building with her foot on the brake. I need to know if there is a way to access the ECM/PCM/ECU for proof that the vehicle had a case of unintended sudden acceleration? Please help. Thank you.

There only 2 ways that I know of at the user level that can access the ECU. HPTuners and EFILive. They are only tools that can edit the data in an ECU to make the engine run differently. (more power etc)
Now, there is a remote chance that the ECU did log a fault code for something like throttle position sensor, but I doubt you would be able to use it for anything. Big car makers know for certain, putting capabilities like that in their systems would be like shooting themselves in the head. They want to stay out of the courts as much as possible.

On another note, don't believe everything you hear. Many years ago, my wife (gently) rear ended a stopped tractor trailer. She swore up and down that he rolled into her(trucks do roll backwards sometimes when they start out) and that she didn't hit him. 2 months later, I noticed a charge on our bank statement from the local town court for $175. I pay the fee for a court documents and found that she was at fault for rear ending him. I interrogated my son, and he said she was texting on the phone when that happened.
So, just because SHE said it happened her way, doesn't always mean it did happen that way.

The only thing I can think of that records SOME vehicle data, is the SDM of the air bag system, if an air bag deploys....the extent of the data, I am not sure....and I think only GM has access to this data....

Only time ECM stores data is when a code is set....no code, nothing......

I got a curiosity question if you don't mind me asking. What kinda of surface was she on? I power brake vehicles all the time to test for misfire under loads and haven't yet had a vehicle accelerate fast enough forward that I could have run into something. You sure she didn't accidentally push the gas thinking it was the brake? I hope your wife is okay! Have you cranked the vehicle to see if it runs off with you?

Good info about GM computers.

GM Air Bag, Black Box, EDR, Event Data Recorder, SDM, Airbag, CDR, Accident, Deployment, Crash Data Retrieval For GM, Saturn, Hummer Vehicles Using The Bosch / Vetronix CDR Tool, Air Bag Recalls, Recall, Deployment Crash Data

The only incident I can think of for unintended acceleration, was a Grand Am......customer said they tried to slow down and car kept going as they slammed on the brakes and the brakes/tires smoked......customer had the foresight to turn ignition off......at the time, customer pointed out the problem to someone that the gas pedal was down.....

After being towed to the shop and looked at, the pedal was in the proper position....car started up fine with no high idle.....found a TSB stating, that water could possibly get into the accelerator pedal cable, and under the right conditions, freeze enough to make the cable stick, when the pedal was released......cable seemed ok...we replaced it and sent it back to GM....customer was afraid of car and traded it in....don't know what happened to car or if it was a one time thing......

Of course we have heard stories about the Toyota Matrix......this did not have an accelerator pedal cable, it is fly by wire.....Pontiac had the Vibe, which essentially was a Matrix with a Pontiac coat......there were two recalls on both cars for sudden acceleration....one was replace the accelerator pedal position sensor, and the second one was to secure the floor mat so it could not interfere with the gas pedal.....