To test the starter setup: take it out of gear, turn on the key, & connect a jumper on the small wire of the starter solenoid. touch the other end to the + battery post.
1. If the starter
doesn't click (using the jumper) the starter solenoid is probably bad or the hot (& heavy) wire is loose.
2. If it does click, it's the starter. Be sure you have good connections, use an alligator clip if you can.
3. If it turns over & starts, the problem is in one of a variety of relays, clutch safety switch (manual trans), or the transmission safety switch (automatic trans). ALL of them can be bypassed with a starter button wired just like the jumper. Use size 12 or 14 wire to be safe since you'll probably want to put the button where the driver can reach it and long thin wires can heat up.
4: If you're a citizen and actually need all the safeguards that Nissans lawyers advised them to put in for liability reasons : Good luck, get a thick manual & knock yourself out.
