How do you turn off check engine light on 2004 Nissan Titan?

To turn off the check engine light on a 2004 Nissan Titan, first, you need to address the underlying issue that triggered the light. Use an OBD-II scanner to read the trouble codes, fix the problem, and then clear the codes using the scanner. Alternatively, you can disconnect the battery for about 15 minutes to reset the system, but this won't fix the underlying issue. If the light remains on after repairs, consult a mechanic for further diagnostics.