Again, dont like resurecting old threads, But hopefully someone will benefit from having this knowledge in the future as starters are easy to diagnose/replace. These diagrams are also all for the 93 nissan hardbody KA24. but it wont be far off from the exterra
Correct diagnostic of Starter Solenoid:
1.Disconnect battery ground cable.
2.Disconnect "M" terminal of starter motor, Fig. 5 .
3.Using a suitable ohmmeter, check continuity between "S" terminal of starter motor and switch body. Continuity should exist. If continuity does not exist, starter solenoid is defective. Replace as necessary.
4.Check for continuity between "S" and "M" terminals of starter motor. Continuity should exist. If continuity does not exist, starter solenoid is defective. Replace as necessary.
**Continuity being 0 Ohms of resistance.
Another issue that is often overlooked, is the clutch interlock/NSS(neutral safety switch)
1.Disconnect the transmission harness connector.
2.Shift the transmission into neutral.
3.Using an ohm meter, check for continuity between terminals a and f. ^Continuity should exist.
4.Shift the transmission into park.
5.Using an ohm meter, check for continuity between terminals a and b. ^Continuity should exist.
6.Shift the transmission into all other positions.
7.Using an ohm meter, check for continuity between terminals a and b. ^Continuity should NOT exist.
8.Using an ohm meter, check for continuity between terminals a and f. Replace the switch if it fails the above test.
You may also have a bad ignition switch(im covering all my bases, hate comebacks)
Disconnect ignition switch connector.
Using an ohm meter/Test Light check for continuity as per the following.
Ignition switch position:
1.OFF No continuity between any terminal.
2.ACCESSORY Continuity between terminals 1 and 2.
3.ON Continuity between terminals 1, 2 and 3.
4.START Continuity between terminals 1, 3, 4 and 5. Replace ignition switch if it fails above tests.
But usually a solid "click" from the starter when trying to start it is either a corrosion issue. Check your cable connections for green gunk. If you think it looks bad, replace it. Usually they are around 10 dollars. You can check the resistance, but even one good strand of wire will read 0 ohms, so its not a failsafe test. But voltage drop over the cable of more than .1 is bad and it will need to be replaced.
You can also bench test the starter by taking it out and giving it direct 12 volts of power to see if it runs, but its not a good test because it may work fine on a bench, but under load of the engine, you may not have the power to turn the engine over.
And as always, CHECK BATTERY VOLTAGE Higher than 9.6 when starting the engine.