BlackZ06

I'd have to believe the SDM would do a parity check (or other memory test) of any memory it writes too, just like the PCM does. If you remove the memory (assuming it's external to the processor chip), I strongly suspect the SDM's internal diagnostics would spot that right away, and throw a DTC and may even "lock" the SDM, as it would consider that a permanent internal failure (Just like a P601-P607 and P1683 in the PCM).

Even if you passed the start-up diagnostics, the SDM actually is writing to that memory all the time, every second in fact that you're driving. It also stores "non-deployment events". Those are impacts that cause the SDM to analyze whether or not to deploy the bags, but then decides the impact is too small (or other parameters make it decide) not to deploy. Those also get written to memory. They disappear after 250 ignition cycles without another "wake-up" of the algorithm. There is more in that memory than just "crash" data.

Take the memory away and the SDM will know it literally a second after you start driving.

Look, unless you can re-program the SDM to NOT write vehicle and crash data to memory, I just don't see how you're gonna get around this thing.

Last time I checked the SDM is somewhere around $400.00 so if you want to buy one and try to reverse engineer it, have at it ....

One thing to keep in mind ... the service manual has ALL KINDS of warnings about replacing the SDM. Basically after a replacement it warns the service tech to NOT be near the airbags the first time you power up the cars ignition. Even removing it is dangerous as you have to be sure to discharge the VLR before you pull the SDM ...

Heck, the airbags scare me more than anything else in my car !!!!

BlackZ06

Ohhhh GREAT idea ......

The SDM is PERMANENTLY LOCKED with its crash data in it FOREVER after an airbag deployment.

I buy an SDM from a wrecked car, only it turns out that car hit another vehicle while doing 176 MPH ... that'll be GREAT when I give that to the cops and say "I was doing under the speed limit when it happened" ....
I'll take my chances with the data in MY SDM, not one from an unknown wreck.

ajderzie

The EDR actually continuously writes to the ROM not the EEPROM. The EEPROM can only be written to once (although it technically has a read/write cycle of about 100 until it degrades). This is why the module needs to be replaced I believe. When the airbags deploy, the data is sent from the ROM to the EEPROM. The near deployment data is sent somewhere else.

Regardless, it is starting to look like the EEPROM shouldn't be tampered with. There are EEPROM writers and reset tools so it seems technically possible to rewrite the EEPROM after the fact, even though Vetronix says it can't be done.

Another possibility of much lower tech might be just relocating the module and placing a dummy in the normal location.

Anyway, food for thought.

BlackZ06

If you have a Service Manual .... look up DTC B1001

The SDM has the vehicle's VIN number programmed in it, and also has a 4 digit number called a "restraints ID" in it (Also called a PROM ID).

The SDM and PCM VIN numbers have to match, and SDM and BCM "restraints ID" have to match. If they don't ... DTC B1001 ....

You'd need a Tech2 to fix this problem ... but it also means that if you try substituting a "fake" SDM after an accident the CDR will spot that the VIN and/or "restraints ID" are incorrect.

ajderzie

Yes, it looks like there is much more that is stored on the eeprom than just the accident data.