How To Test The Starter Motor (2002-2006 2.5L Nissan Sentra, Altima)

You can test the starter motor on your 2.5L Nissan Sentra (or Altima) in three steps.

I'll explain how in a step-by-step way. You'll be able to find out if the starter motor is defective (or not) without having to remove it to bench test it.

Important Safety Tips And Precautions

TIP 1: As mentioned at the beginning of the tutorial, you don't have to remove the starter motor to test it. In the illustrations I've made you'll notice that it's removed, but this is just to facilitate the explanation of your test connections.

If the starter motor is already removed, you can bench-test it and the following tutorial will help you: How To Bench Test A Starter Motor (Step By Step).

TIP 2: Your Nissan Sentra's battery should be fully charged before beginning any of the tests in this tutorial. Performing the tests with a less than fully charged battery may give you a false test result.

It's also very important that the battery terminals and post be absolutely clean before starting any of the test.

TIP 3: If your Nissan Sentra (Altima) comes equipped with a standard transmission, be sure and place it in neutral before starting any of the test. Don't forget to activate the parking brake.

TIP 3: You may need to raise your vehicle, with a jack, to access the starter motor. Don't trust the jack to keep your vehicle up in the air, use jack stands!

Symptoms Of A Bad Starter Motor

The most common end result of a bad starter motor is that the engine in your 2.5L Nissan Sentra will not turn over when you turn the key to crank and start it.

The other type of problem is an intermittent failure that makes the starter motor fail some of the time.

Intermittent starter motor problems can be a challenge to resolve. The most important thing to remember, in this type of starter motor problem, is that you'll have to wait till the engine is not cranking to test it.

You'll see one of the following symptoms when the starter motor fails:

1. When you turn the key to start your the engine, nothing happens.
2. Jump starting the engine doesn't make it crank over.
3. The battery has been charged and/or replaced and still your Nissan Sentra does not crank.
4. When you turn the key to crank the engine, all you hear is a small knock and nothing else.

Tools Needed To Test The Starter Motor

Testing the starter motor on your 2.5L Nissan Sentra (Altima) doesn't require expensive or exotic diagnostic tools. Here's a list of the tools you'll need to successfully test it:

1. Remote starter switch.
   • If you'd like to see what a remote starter switch looks like, you can follow this link: Innova 3630 Remote Starter Switch (Amazon affiliate link).
   • You can either buy this tool online or you can buy it at your local auto parts store (AutoZone or O'Reilly Auto Parts, etc.).
2. Multimeter or a 12 Volt automotive test light.
   • If you don't have a multimeter or need to upgrade yours, check out my recommendation here: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).
3. A wire piercing probe.
   • This tool is not an 'absolute must-have tool' but I can tell you from experience that it makes it a whole lot easier to probe the S terminal wire for the start signal.
   • If you'd like to see what this tool looks like, you find out more about it here: Wire Piercing Probe Tool Review (Power Probe PWPPPPP01).
4. A helper.

As mentioned before, the tools you need to test the starter motor won't break the bank. OK, let's turn the page and get started with the first starter motor test.

TEST 1: Applying 12 Volts To The Starter Motor S Terminal

In this very first test section, we're gonna' bypass the ignition switch and apply 12 Volts directly to the starter motor's S terminal (to see if it activates and cranks the engine).

If the starter motor is OK, then it'll crank your Nissan Sentra or Altima's engine. If the starter motor is defective, then applying 12 Volts to it won't activate it.

The fastest, easiest, and the safest way to apply this voltage to the starter motor is with a remote start switch. You can find an example of this tool here: Innova 3630 Remote Starter Switch (Amazon affiliate link).

IMPORTANT: Remove the key from your Nissan Sentra or Altima's ignition switch to prevent the engine from accidentally starting.

IMPORTANT: Place your Nissan Sentra (Altima) on jack stands if you raise it to access the starter motor!

OK, these are the test steps:

1. 1

   Disconnect the battery negative (-) terminal.
   
   You'll reconnect it back in one of the following steps, for now, it's a safety precaution as you set up the test.

2. 2

   Disconnect the wire that connects to the S terminal of the starter motor. This wire has a female terminal that connect to the male spade terminal on the starter motor's solenoid.

3. 3

   Attach one of the alligator-type terminals of the remote starter switch to the S terminal of the starter motor.

4. 4

   Reconnect the battery negative (-) cable to the battery negative (-) post.
   
   NOTE: Make sure that the battery cables and posts are clean.

5. 5

   Connect the remaining alligator-type terminal of the remote starter switch to the battery positive (+) post.
   
   IMPORTANT: If your Nissan Sentra has a standard transmission, make sure it's out of gear before you make this last connection.

6. 6

   Activate the starter motor with your remote starter switch. As you apply these 12 Volts (to the S terminal of the starter motor), you'll get one of two results:
   
   1) The starter will activate and will turn over the engine -OR- 2) The starter motor won't do a thing.

Let's see what your test result means:

CASE 1: The starter motor cranked the engine. This is the correct and expected test result. You can conclude that the starter motor itself is not defective and thus not behind the problem causing the engine not to crank.

Since the engine isn't turning over (when you turn the key to crank and start it), we need to see if it's receiving the activation signal from the ignition switch. Go to: TEST 2: Verifying The Start Signal.

CASE 2: The starter motor DID NOT crank the engine. This usually means that your Nissan Sentra's starter motor is bad and needs to be rebuilt or replaced.

Before you replace it, I recommend that you do a voltage drop test on the battery cable that connects to the starter motor's solenoid. This is a very simple multimeter test and you can find it here: TEST 3: Voltage Drop Testing The Battery (+) Cable.

I'm also gonna' suggest that you perform TEST 2 just to tie up any loose ends. Go to: TEST 2: Verifying The Start Signal.

If the above two tests confirm that the start signal IS present and there's no voltage drop on the battery cable (feeding battery power to the starter motor), then you can confidently conclude your Nissan Sentra's starter motor is bad and needs to be replaced.

TEST 2: Verifying The Start Signal

As you're probably already aware, the starter motor gets its start signal from the ignition switch.

This start signal reaches the starter motor thru' the wire that connects to the starter solenoid's S terminal.

In this test section, we're gonna' see if the start signal is actually present when we turn the key and try to crank and start the engine.

These are the test steps:

1. 1

   Disconnect the wire that connects to the S terminal of the starter motor solenoid.

2. 2

   Connect the red multimeter test lead to the female terminal of the wire you just disconnected from the S terminal of the starter motor.

3. 3

   Attach the black multimeter test lead to a clean and rust-free spot on the engine or on the vehicle frame.
   
   I recommend that you use a battery jump start cable to Ground the black multimeter test lead directly to the battery negative (-) terminal.

4. 4

   Have your helper crank the engine from inside your Nissan Sentra (Altima).
   
   The engine won't turn over, but the idea is to verify that the starter motor's internal solenoid is getting the 12 Volt start signal from the ignition switch (or not).

5. 5

   Your multimeter is going to register one of two results: Either 9 - 12 Volts DC or no voltage at all.

Let's examine your test result:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct and expected test result. You can conclude that your Nissan Sentra or Altima's starter motor is getting the start signal.

You can also conclude that the ignition switch and safety neutral switch are not defective.

The next test is to check the battery cable that connects to the starter motor. Go to: TEST 3: Voltage Drop Testing The Battery (+) Cable.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. This test result lets you know that the start signal is missing and that this is the reason that the starter motor is not cranking your Nissan Sentra or Altima's engine.

The most common cause of this missing start signal is usually a bad neutral safety switch or a bad ignition switch. Although it's beyond the scope of this tutorial to test these two, you have eliminated the starter motor as a cause of the problem.

TEST 3: Voltage Drop Testing The Battery (+) Cable

Our last test is a voltage drop test of the battery cable that connects the battery to the starter motor.

This battery cable is the one that delivers the current (from the battery) that the starter needs to turn the engine over.

In some cases, this battery cable will have hidden corrosion that keeps a lot of the current from reaching the starter motor. The end result is a starter motor that won't crank the engine and that gives the impression of being defective.

IMPORTANT: Don't disconnect the battery cable from the starter motor's solenoid. In the illustration the battery cable is disconnected from the starter motor just to make it easier to show the multimeter test connections.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Attach the red 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

   With the black multimeter test lead, touch the center of the starter S terminal stud to which the big battery cable attaches to. You'll maintain the black multimeter test lead in this position throughout the next step.

4. 4

   Have your helper crank the engine even though the starter motor isn't cranking 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 5 Volts DC).

Let's interpret your voltage drop test result:

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

You can conclude your Nissan Sentra's starter motor is defective if you have:

1. Confirmed that the starter motor doesn't work when you apply power to the S terminal wire of the starter motor (TEST 1).
2. Confirmed that the starter motor is receiving the crank signal (TEST 2).
3. In this test step, you have confirmed that no voltage drop exists on the battery positive cable.

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. This is to make sure that the engine or the A/C compressor have not locked up and causing the no-crank condition.
• Bench test the starter motor after removing it. This is a super easy test to do and this tutorial will help: How To Bench Test A Starter Motor (Step By Step).

CASE 2: Your multimeter registered 5 Volts or more. This result tells you that a voltage drop does exist and that the battery's full power 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 the 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.

More 2.5L Nissan Tutorials

To see all of the 2.5L Nissan Sentra and Altima specific tutorials, go to:

• Nissan 2.5L Index Of Articles.

Here's a sample of the tutorials, you'll find in the Index of Articles:

• Coil-On-Plug (COP) Coil TEST 2.5L Nissan Altima, Sentra (2002-2006).
• How To Test Engine Compression (2.5L Nissan Altima, Sentra).
• Testing A Bad Alternator: Symptoms And Diagnosis.
• How To Bench Test The Starter Motor.
• How To Troubleshoot a Blown Head Gasket (2.5L) (at: troubleshootmyvehicle.com).