How To Test The CMP Sensor (1996, 1997, 1998 1.5L Mazda Protege)

The camshaft position (CMP) sensor is located inside the distributor on your 1.5L Mazda Protege.

It can be easily tested with a multimeter, no expensive diagnostic test equipment needed!

In this tutorial I'll explain how to do it so that you can find out if camshaft position sensor is bad or not.

En Español You can find this tutorial in Spanish here: Cómo Probar El Sensor CMP (1996-1998 1.5L Mazda Protege) (at: autotecnico-online.com).

APPLIES TO: This CMP sensor diagnostic tutorial applies to the following vehicles:

  1. 1996 1.5L Mazda Protege (with Federal Emissions).
  2. 1997, 1998 1.5L Mazda Protege.

RELATED WIRING DIAGRAMS:

  1. Ignition System Wiring Diagram (1996 1.5L Mazda Protege -Federal Emissions).
  2. Ignition System Wiring Diagram (1997-1998 1.5L Mazda Protege).

NOTE: You can find the ignition coil and ignition control module tests here: How To Test The Ignition System (1996-1998 1.5L Mazda Protege).

Important Tips And Suggestions

TIP 1: To test the camshaft position sensor's signal, you'll need to turn the engine by hand. To be a bit more specific, you cannot use the starter motor to crank the engine to perform TEST 3.

TIP 2: Before you test the camshaft position sensor, you must first test the ignition coil. If the ignition coil sparks then you can conclude that the camshaft position sensor is good and functioning correctly.

The ignition coil test is not hard to and you can find it here: How To Test The Ignition System (1996-1998 1.5L Mazda Protege).

TIP 3: If it turns out that the camshaft position sensor is bad, you're gonna' have to buy the whole distributor, since Mazda in all its wisdom, does not license any of the components to be sold separately.

How Does The Camshaft Position Sensor Work?

Here's a very brief description of how the camshaft position (CMP) sensor works:

  1. The camshaft position sensor is located inside the distributor and is part of the ignition control module assembly.
  2. The CMP sensor assembly is really a crankshaft position sensor, since the fuel injection computer uses it to control the creation of spark (thru') the ignition control module and ignition coil.
  3. Now, when you turn the key and crank the engine (to start it), the camshaft position sensor gets power thru' the white with red stripe (RED/WHT) wire of the distributor's 7-wire connector.
  4. As the engine turns, the CMP sensor assembly starts to create an ON/OFF voltage signal that it sends directly to the computer.
  5. When the computer gets the CMP signal, it does its little song and dance and shoots an activation signal to the ignition control module.
  6. This ignition control module activation signal can be checked with a multimeter that can read Hertz frequency (which you can do in: How To Test The Ignition System (1996-1998 1.5L Mazda Protege)).
  7. When the ignition control module gets its activation signal from the fuel injection computer, it now starts to switch the ignition coil's power ON and OFF. This ON/OFF action is what makes the ignition coil spark and is referred to as the switching signal.

When the camshaft position sensor fails on your 1.5L Mazda Protege; the engine is not going to start due to a lack of spark.

You may also see a P0340 trouble code registered in the fuel injection computer (but not always).

TEST 1: Making Sure The CMP Sensor Is Getting Power

Making Sure The CMP Sensor Is Getting Power. How To Test The CMP Sensor (1996, 1997, 1998 1.5L Mazda Protege)

In this first test we're gonna' make sure that the camshaft position (CMP) sensor is getting 10 to 12 Volts.

The wire that feeds these 12 Volts to the camshaft position sensor is the white with red stripe (WHT/RED) wire of the distributor's 7-wire connector.

The WHT/RED wire connects to the female terminal I've labeled with the letter B in the photo above.

If 12 Volts are present, then the next step is to make sure the CMP sensor is getting Ground (TEST 2).

If you don't have a multimeter and need to buy one, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at: easyautodiagnostics.com.

These are the test steps:

  1. 1

    Place your multimeter in Volts DC mode.

  2. 2

    Disconnect the 7-wire connector from the distributor.

  3. 3

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

  4. 4

    Turn the key to the ON position but don't crank the engine.

  5. 5

    Gently probe the female terminal labeled with the letter B with the red multimeter test lead.

  6. 6

    Your multimeter should register 10 to 12 Volts DC.

Let's examine your test result:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct test result and it confirms that your Mazda Protege's CMP sensor is getting power.

The next step is to make sure that it's getting Ground. Go to: TEST 2: Making Sure The CMP Sensor Is Getting Ground.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. Without this voltage the CMP sensor will not function.

Your next step find out why this voltage is missing and repair the problem. The following ignition system wiring diagrams will help you trace down the problem:

  1. Ignition System Wiring Diagram (1996 1.5L Mazda Protege -Federal Emissions).
  2. Ignition System Wiring Diagram (1997-1998 1.5L Mazda Protege).

Mazda Vehicles:

  • Protege 1.5L
    • 1996
      1997
      1998