DTC 21

Check Engine Light indicates trouble code 21:

Most likely a problem in the VTEC Solenoid Valve.

DTC 21 - VTEC Solenoid Valve Page 1:

DTC 21 - VTEC Solenoid Valve - Page 2:

The Check Engine warning light may come on, indicating a system problem, when, in fact, there is a poor or intermittent electrical connection. First, check the electrical connections, clean or repair connections if necessary.