A programmed microprocessor has a learning mode of operation wherein data
to and from a circuit coupled to a wiring harness in a vehicle is stored
by the microprocessor. After the learning mode is completed, removal of
the circuit does not cause an error condition because appropriate data is
supplied instead by the microprocessor. A sleep mode of operation
prevents the microprocessor from interfering with the operation of the
circuit when the circuit and the microprocessor are coupled to the wiring
harness.