How To Test The Starter Motor (1996-1997 3.3L Pathfinder)

TEST 4: Voltage Drop Testing The Battery (+) Cable

In this test section, we're gonna' make sure that full battery current is reaching the starter motor by doing a simple multimeter voltage drop test on the cable that delivers this battery current to the starter motor.

IMPORTANT: The battery must be connected to its two battery cables. The inhibitor relay must be in its place in Relay Box #2. The S terminal wire must be connected to the S terminal on the starter motor solenoid. The battery (+) cable must be connected to the starter motor.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Attach the black multimeter test lead to the center of the positive (+) battery terminal.
   
   If the positive battery post isn't clean, clean a spot right on the top of it. It's important that the multimeter lead make contact right in the center of the positive battery post.

3. 3

   Connect the black multimeter test lead to the center of the stud to which the big battery cable attaches to on the starter solenoid.

4. 4

   Have your helper crank the engine even though the starter motor will not crank the engine.
   
   This is important, since a voltage drop test has to be done while the component in question is working (or trying to work).

5. 5

   If all is good (no voltage drop), your multimeter will register 0 Volts (.5 Volts is still 0 Volts).
   
   If there's a voltage drop (which is bad), your multimeter will register voltage (usually above 7 Volts DC.)

Let's take a look at what your results mean:

CASE 1: Your multimeter registered 0 Volts (no voltage drop). This is the correct test result and tells you that the starter motor is receiving all of the battery current it needs to crank your Nissan Pathfinder's engine.

You can conclude the starter motor is bad if you have:

1. Confirmed that the starter motor DOES NOT crank the engine when you bypass the inhibitor relay (TEST 1).
2. Confirmed that the starter motor DOES NOT crank the engine when you apply battery power to the S terminal of the starter motor's solenoid (TEST 2).
3. Confirmed that the starter motor is receiving a Start Signal (TEST 3).
4. Confirmed that no voltage drop exists on the battery positive cable (this test step).

Replacing the starter motor should solve your no-crank condition.

I'm going to make two more recommendations to you:

• Before removing the starter motor, manually turn the engine using a 1/2 ratchet and the appropriate socket on the crankshaft pulley. This is to make sure that the engine or the A/C compressor have not locked-up. If the engine is locked-up then the engine will not crank and it'll look like the starter motor is at fault.
• Bench test the starter motor after removing it. This is a super easy test to do and this tutorial will help: Bench Testing The Starter Motor.

CASE 2: Your multimeter registered 5 Volts or more. This result tells you that a voltage drop does exist and that full battery current is not reaching the starter motor.

The good news is that this can easily be corrected, since a voltage drop is always caused by some sort of corrosion issue on the battery positive cable or terminals or the battery positive post.

The solution is to thoroughly clean the battery positive post and the battery positive (+) terminal (both the end that attaches to the battery positive post and the end that connects to the starter motor's battery (+) cable stud.

After cleaning, try cranking the engine. If it cranks and starts, no further testing is required.

TEST 5: Making Sure The Inhibitor Relay Is Getting A Start Signal

If you've reached this point, then you've confirmed that:

• The starter motor cranks the engine only when the inhibitor relay is bypassed (TEST 1).
• The starter DOES NOT crank the engine when the inhibitor relay is in its place on Relay Box #2.

There's a good chance that the inhibitor relay is not receiving a Start Signal from the ignition switch.

So in this section we're gonna' check for the presence of the Start Signal on the terminal labeled with the number 3 (in the photo above) when you turn the key to start the engine.

These are the test steps:

1. 1

   Remove the inhibitor relay from Relay Box #2.

2. 2

   Connect the red multimeter test lead to the female terminal labeled with the number 3 in the photo above.
   
   NOTE: Gently probe the female terminal in the relay socket with your multimeter test lead to avoid damaging it.

3. 3

   Connect the black multimeter test lead to the battery negative (-) terminal.

4. 4

   Have your helper turn the key to crank the engine.
   
   NOTE: The engine is not gonna' start but to check for the Start Signal you need to have your helper turn the key to start the engine.

Let's examine your test results:

CASE 1: 10 to 12 Volts are present when the key is turned to start the engine. This is the correct test result and lets you know that the ignition switch is providing a Start Signal to the inhibitor relay.

The next step is to check that the inhibitor relay is getting an Inhibitor Switch Signal. For this test go to: TEST 6: Testing The Inhibitor Switch Signal.

CASE 2: 10 to 12 Volts ARE NOT present when the key is turned to start the engine. Without a Start Signal the inhibitor relay will not activate the starter motor.

The most likely cause of this missing Start Signal is a bad ignition switch. Your next step is to test the ignition switch.