Mystery black box

tracker thread is pretty much dead so thought i would post it here
on my 92 geo tracker i was taking the computer out to swap it with another one to see if it got rid of the miss/surge problem there was a black plastic box screwed to the firewall below the computer. i thought it was a aftermarket car alarm box till i took it out and looked at it. says suzuki and K*H AT9479 and seems to plug into the stock car wiring harness. box is about 6" x 8" x1". seems to run fine with it out of the car, anyone have any ideas? the car is a 5 speed 4x4 so its not the automatic transmission computer

no that the RWAL, rearwheel antilock brake Puter.

with automatic there are 3 puters

ECU
TCU
RWAL

each as a light, each has reset ,each has codes to view.

http://carfix.stufftoread.com/

it does not have antilock brakes