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: Bench Testing The Starter Motor.

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 pick up or SUV 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: Sunpro Actron CP7853 Remote Starter Switch.
   • You can either buy this tool online or you can buy it at your local auto parts store (AutoZone, O'Reilly, Pepboys, 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: Buying A Digital Multimeter For Automotive Diagnostic Testing.
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: Sunpro Actron CP7853 Remote Starter Switch.

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.