How To Test The TPS (1995-1998 1.5L Mazda Protege)

In this tutorial I'm gonna' show you how to test the throttle position sensor (TPS) on the 1995-1998 1.5L Mazda Protege.

The test is done with a multimeter, no scan tool required! All of the test steps are explained in a step-by-step manner.

In 3 tests you'll be able to easily diagnose the throttle position sensor as bad (or not).

ES You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1995-1998 1.5L Mazda Protege) (at: autotecnico-online.com).

APPLIES TO: This tutorial on testing the TPS applies to the following vehicles:

• 1.5L Mazda Protege: 1995, 1996, 1997, 1998.

RELATED TROUBLE CODES:

• P0122 -What Does It Mean? (1996-1998 1.5L Mazda Protege).
• P0123 -What Does It Mean? (1996-1998 1.5L Mazda Protege).

Symptoms Of A Bad Throttle Position Sensor

It's the throttle position sensor's job to measure the throttle plate angle as it opens or closes as you step on or off the accelerator pedal.

In a nutshell, the throttle position sensor produces a voltage signal that increases as you step on the accelerator pedal and the throttle plate opens.

As you step off the accelerator pedal, the throttle plate starts to close and the TPS voltage signal decreases back to its original base voltage.

All of these throttle plate angle changes are constantly reported to the fuel injection computer on your 1.5L Mazda Protege.

Since the throttle position sensor (TPS) is such an important component of the engine management system, when it fails, you're gonna' definitely feel the engine resent it.

You're going to see the following TPS diagnostic trouble code lighting up the check engine light:

• P0121 Throttle Position Sensor Performance Problem.
• P0122 TPS Voltage Too Low.
• P0123 TPS Voltage Too High.

You're also going to see one or more of the following symptoms:

• Won't pass the emissions test.
• Bad gas mileage.
• Lack of power, rough idle, or hesitation.
• Engine cranks a long time before starting.

Throttle Position Sensor (TPS) Circuit Descriptions

Below are the circuit descriptions of the 3 wires of the throttle position sensor's connector.

Terminal	Wire	Description
1	Light Green With Red Stripe (LT GRN/RED)	5 Volts
2	Light Blue With Yellow Stripe (LT BLU/YEL)	TPS Signal
3	Black With Red Stripe (BLK/RED)	Ground

Where To Buy The TPS And Save

The following links will help you to comparison shop for the throttle position sensor on your 1.5L Mazda Protege:

NOTE: The above throttle position sensor (TPS) fits the following vehicles: 1995, 1996, 1997, 1998 1.5L Mazda Protege.

TEST 1: Testing The TPS Voltage Signal

For our very first test, we're gonna' make sure that the throttle position sensor is creating a voltage signal that increases/decreases as you open/close the throttle plate.

We're going to connect multimeter to the blue with yellow stripe (BLU/YEL) wire of the sensor's 3-wire connector.

The BLU/YEL wire is one that carries the TPS voltage signal to your Mazda Protege's fuel injection computer.

In the photo above, I have labeled the BLU/YEL wire with the number 2.

If the throttle position sensor is bad, you'll see that the TPS voltage signal stays stuck in one value as you open/close the throttle plate.

IMPORTANT: The throttle position sensor (TPS) must remain connected to its electrical connector for this test to function properly. To be able to access the voltage inside the signal wire, you'll need to use either a back probe or a wire piercing probe. You can see an example of this tool here: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Let's get started:

1. 1

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

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Ground the black multimeter test lead directly on the battery negative (-) post.

4. 4

   Connect the red multimeter test lead to the blue with yellow stripe (BLU/YEL) wire of the TP sensor harness connector.
   
   The BLU/YEL wire is identified with the number 2 in the photo above.
   
   NOTE: The TP sensor must remain connected to its 3-wire connector to read the signal in the BLU/YEL wire.

5. 5

   At this point, the multimeter should read a value between 0.4 to 0.9 Volts DC.

6. 6

   Manually rotate the throttle plate.
   
   You'll get the best results by opening and closing the throttle plate directly on the throttle body instead of stepping on the accelerator pedal.

7. 7

   The multimeter should show an increasing voltage as you (or your helper) open up the throttle plate.
   
   You'll get the best results by opening and closing the throttle plate directly on the throttle body instead of stepping on the accelerator pedal.

8. 8

   The multimeter should show a decreasing voltage as you begin to close the throttle plate.

9. 9

   Using a screwdriver's handle, gently tap the TP sensor as you open and close the throttle plate and observe the multimeter.
   
   The purpose (of tapping the TP sensor with the screwdriver's handle) is to see if the TP sensor shows gaps in the voltage signal. Why? Because a good TP sensor will show a continuous increasing or decreasing voltage signal even while getting tapped by the screw-driver's handle.

Let's analyze your test results:

CASE 1: The TPS voltage signal increased/decreased as you opened/closed the throttle plate. This is the correct test result and it indicates that the throttle position sensor is good.

With this test result you can also conclude that the TPS sensor is getting both power (5 Volts) and Ground from the fuel injection computer.

CASE 2: The TPS voltage signal DID NOT increase/decrease as you opened and closed the throttle plate. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is bad the next step is to check that the LT GRN/RED wire is feeding the TPS with 5 Volts. For this test go to: TEST 2: Making Sure The TPS Has 5 Volts.

CASE 3: The multimeter DID NOT register any voltage. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is bad the next step is to check that the LT GRN/RED wire is feeding the TPS with 5 Volts. For this test go to: TEST 2: Making Sure The TPS Has 5 Volts.

TEST 2: Making Sure The TPS Has 5 Volts

So far, in TEST 1, you've confirmed that the throttle position sensor is not producing a voltage signal that increases/decreases as you open/close the throttle plate.

There's a good chance that the throttle position sensor might not be receiving 5 Volts DC from the fuel injection computer.

So, in this test section, we're going to make sure that the light green with red stripe (LT GRN/RED) wire is supplying 5 Volts DC to the TPS.

In the photo above, the LT GRN/RED wire connects to the female terminal labeled with the no. 1.

If 5 Volts are present in the LT GRN/RED wire, then we can move on to the next test which is making sure that the throttle position sensor is receiving Ground.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the TPS from its electrical connector.

3. 3

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

4. 4

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

5. 5

   With the red multimeter test lead (using the appropriate tool), gently probe the female terminal labeled with the number 1.
   
   Terminal 1 connects to the LT GRN/RED wire of the connector.

6. 6

   Your multimeter should read 4.5 to 5 Volts DC.

Let's analyze your test results:

CASE 1: The LT GRN/RED wire is feeding the TPS with 5 Volts. This is the correct test result.

Now that you have confirmed that your 1.5L Mazda Protege's TPS is getting 5 Volts, the next step is to make sure it's getting Ground. Go to: TEST 3: Making Sure The TPS Has Ground.

CASE 2: The LT GRN/RED wire IS NOT feeding the TPS with 5 Volts. Without these 5 Volts the TPS, on your 1.5L Mazda Protege, will not function.

These missing 5 Volts are usually the result of an open-circuit problem in the LT GRN/RED wire between the TPS sensor's connector and the fuel injection computer's connector.

TEST 3: Making Sure The TPS Has Ground

If you've reached this point, your TPS diagnostic test results have confirmed that:

• The TPS is not producing a voltage signal that increases/decreases as you open/close the throttle plate (TEST 1).
• The TPS is getting 5 Volts on the LT GRN/RED wire (TEST 2).

For our third and last test, we're gonna' make sure that the throttle position sensor is receiving Ground from the fuel injection computer.

The wire that supplies Ground do the TPS, is the black with red stripe (BLK/RED) wire of the sensor's 3-wire connector.

In the photo above, the BLK/RED wire connects to the female terminal labeled with the no. 3.

To test for the presence of Ground in the BLK/RED wire, we're gonna' to do a simple multimeter voltage test.

NOTE: Ground is provided by the fuel injection computer of your 1.5L Mazda Protege. Be careful and don't connect this wire to battery 12 Volts or you'll fry the fuel injection computer. The multimeter voltage test I'm suggesting below is a safe way to test for the presence of Ground in the wire.

Let's get started:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the TPS from its electrical connector.

3. 3

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

4. 4

   Connect the red multimeter test lead to the positive (+) battery terminal.

5. 5

   With the black multimeter test lead (using the appropriate tool), gently probe the terminal labeled with the number 3.
   
   Terminal 3 connects to the BLK/RED wire of the connector.

6. 6

   Your multimeter should read 10 to 12 Volts DC.

Let's analyze your test results:

CASE 1: The BLK/RED wire is feeding Ground to the TPS. This is the correct test result.

You can correctly conclude that the TPS is defective if you have:

• Confirmed that the TPS voltage signal does not increase/decrease as you opened/closed the throttle plate (TEST 1).
• Confirmed that the TPS is getting 5 Volts (TEST 2).
• Confirmed, in this test section, that the TPS is getting Ground.

CASE 2: The BLK/RED wire IS NOT feeding Ground to the TPS. Without Ground the TPS will not function.

This missing Ground is usually caused by an open-circuit problem in the BLK wire between the throttle position sensor's connector and the fuel injection computer's connector.

More 1.5L Mazda Protege Tutorials

You can find a complete list of 1.5L Mazda Protege tutorials in this index:

• Mazda 1.5L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• Ignition System Wiring Diagram (1995 1.5L Mazda Protege).
• MAF Sensor Circuit Wiring Diagram (1996-1998 1.5L Mazda Protege).
• How To Test The MAF Sensor (1996-1998 1.5L Mazda Protege).