Nissan K21 or K25 engine? Correct?

You can do it through the pedal.

Turn key on, wait three seconds.
Press and release the pedal five times within five seconds or less.
After the fifth release leave it up for seven seconds.
After the full seven seconds press it for a full ten seconds.

After ten seconds release the pedal and the dash display will flash error codes and hours (looks different then just the key on). This is how you know you got in.

After you're in, just hold the pedal down another full ten seconds to clear the fault codes. It should just flash hours if it is successful.

If at some point you screw up, reset the key and start over. The timing is very critical. Using a stopwatch or something may help.

Some codes IIRC can only be cleared with the laptop. I don't remember if this is one of them offhand.

FYI: Most Nissan cars use the same exact procedure for clearing ECM codes. My old Maxima and my Ex-GF's Pathfinder did.