From the 700/900 FAQ's:

http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

2. Erasing Fault Codes. After you have retrieved all the Fault Codes in step 1 above, you should erase the system memory.
Repeat step 1 above and read the fault codes again
Press and hold the button for more than five seconds, then release it.
When the LED lights, press the button again for more than five seconds and release. If the LED goes off, then the memory is cleared.
To test that memory is cleared, press the button again for >1 second and <3 seconds. If code 1-1-1 is returned, then the memory is cleared.
Repeat step 1 above with the other cable position mode (2 or 6) to erase FI or ignition codes.
If you cannot erase the code, yet you feel the problem has been fixed, then turn the ignition off and disconnect the battery ground for a few seconds. This will clear all the codes. After starting the engine, if the code does not reappear, then you've fixed the problem. If you obtain another code, then you've still got the fault.