I finally cracked the Odometer and SRS ECU code

[CTScott]

One can purchase very expensive, off the shelf, systems for reprogramming the mileage in a cluster and for resetting the "black box" data in the SRS ECU after a crash, where the airbags deploy. I decided to forgo the expense and try to develop my own.

In both ECUs the data is stored in a EEPROM on circuit board of the device. In the picture below, of the inside of the SRS ECU, the EEPROM is circled.



When I finished repairing my latest project Yaris (AKA Crashy2), I found that even after resetting the SRS ECU's stored codes (DTCs) with my TechStream tool, the SRS light still remained on on the cluster. After doing a bit of research I found out that the light remains lit because the SRS ECU stores data when a crash occurs, where the airbag(s) deploy. Normally a repair shop simply replaces the SRS ECU along with the airbags, but clearing the data from the EEPROM will also correct the issue (and there are quite a few vendors on eBay who will do this for a fee).

I pulled the SRS ECU from my 09 Yaris and read the EEPROM. I compared the data with the data from Crashy2's SRS ECU and cleared the locations that differed. After doing so and reconnecting Crashy2's SRS ECU, the SRS light now lights up for a couple of seconds, when the ignition is turned on, and then goes off (which is the normal behavior).

After building a rig to work with the EEPROM from the SRS ECU, I decided to do some experimentation with the instrument cluster (of which I have been amassing a collection of, when I find good deals on them). The cluster turned out to be quite a bit trickier to crack, but this weekend I finally did so.

Here's an 08 cluster that I started my experimentation with:


Once I figured out how the data was encoded, I found that I could change to value to whatever I wanted:






I could then also take a completely different cluster and program it with the same mileage as my original experimental cluster:




Tampering with the odometer on a vehicle is about as illegal as it gets, but swapping a vehicle's cluster with one with lower mileage achieves the same effect, so it is kind of handy being able to reprogram clusters for those desiring to swap theirs out for one of a different year (i.e. from the 06-08 white cluster to the 09-11 orange one), or with different features (i.e. tach).