So is mine. It tests fine at AutoZone, but the guy said it was on because the engine was swapped. Any ideas on how to turn it off?

2000 Civic Si - Swapped for B18B1

 

What specific code(s) were retrieved? If you don't know, retrieve them yourself at home (see link in my signature). Post the codes in this thread.

 

Results:
3 MAP - manifold absolute pressure sensor
22 VTEC pressure valve
23 Knock sensor
41 Primary oxygen sensor heater

22 makes sense, the B18B1 isn't VTEC. Mind explaining the others and common fixes?

 

As mentioned by the guy at AutoZone, first look into the possibility that the CEL codes indicate an incompatibility between sensors that the 2000 Si ECU expects to see and those of the B18B1 engine. For example, does the B18B1 lack a knock sensor? Are the primary O2 sensors different for the two engines? Also look into the possibility that problems lie with differences between the B16 and B18 engine wire harnesses. Hopefully, some of the forum's engine swap experts can help you further with the details.

 

Yea, B18B1 doesn't have VTEC, which leads me to believe you didn't swap the ECU. Get the B18B1 ECU, and I bet your codes all go away.