You might have a toasted CPU.

You can try this at your own risk:
Try removing the Positive terminal for ten minutes then short that cable end to
to the Neg cable and or ground for a minute to insure that the microprocessors
are discharged. You might get lucky

WARNING Don't take a CPU connector off with the battery connected!

If above doesn't work try disconnecting the battery and reseat the CPU
connectors. Use a light spray of silicone on the pins when off.

The OBD is run directly from the CPU's. I had to reseat the ABS CPU connector
to resolve an OBD failure. The connecter went on tough until a little silicone
spray solved that issue.

Good luck, Bill