How To Test The TP Sensor (1998-2002 1.8L Toyota)

TEST 2: Checking Throttle Position Sensor (TPS) Power

Your Toyota's PCM feeds the throttle position sensor with 5 Volts DC thru' the YEL (yellow) wire.

This voltage can be easily verified with your multimeter and that's exactly what we'll do in this test section.

NOTE: You'll be checking for this voltage on the sensor's harness connector but you should avoid probing the connectors front terminals. Instead, you should back-probe the connector with the appropriate tool or use a wire-piercing probe.

With the multimeter in Volts DC mode, this is what you need to do:

1. 1

   Connect the red multimeter test lead to the YEL wire of the TPS harness connector
   
   This is the wire that connects to the terminal labeled with the number 1.

2. 2

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

3. 3

   Have a helper turn the key to the On position, but don't crank or start the engine after the multimeter test leads have been set up.

4. 4

   Your multimeter should register 4.5 to 5 Volts DC if the YEL wire is feeding the throttle post ion sensor (TPS) with power.

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

CASE 1: The multimeter registered 4.5 to 5 Volts DC. This is the correct and expected test result.

Your next step is to make sure that the TPS is getting Ground on the BRN (brown) wire. For this test, go to: TEST 3: Checking Throttle Position Sensor (TPS) Ground.

CASE 2: The multimeter DID NOT register 4.5 to 5 Volts DC. This tells you that the TPS is not getting power and that this the reason why the TPS did not create a voltage signal in TEST 1.

Although it's beyond the scope of this tutorial to find the reason why these 5 Volts are missing, you'll need to get yourself a wiring diagram (for your particular mini-van) and check the continuity of this wire between the TPS and the PCM.

TEST 3: Checking Throttle Position Sensor (TPS) Ground

Now that you've confirmed that the throttle position sensor (TPS) is getting power on the YEL wire, in this test section you'll verify that the BRN (brown) wire of the TPS harness connector is providing Ground.

To confirm that this BRN wire is feeding Ground, we'll do another voltage test with the multimeter.

NOTE: Be careful and do not short this wire to battery voltage, or you'll fry your Toyota's PCM.

These are the test steps:

1. 1

   Connect the black multimeter test lead to the BRN wire of the TPS harness connector
   
   This is the wire that connects to the terminal labeled with the number 2.

2. 2

   Connect the red multimeter test lead directly on the battery's positive (+) terminal.

3. 3

   Have a helper turn the key to the On position, but don't crank or start the engine after the multimeter test leads have been set up.

4. 4

   Your multimeter should register 12 Volts DC if the BRN wire is feeding the throttle position sensor (TPS) with Ground.

Let's analyze your multimeter test results:

CASE 1: The multimeter registered 12 Volts DC. This tells you that the TPS is getting Ground. Now, after having done TEST 1 and TEST 2, you can conclude that the TPS is bad and needs to be replaced.

Here's why:

1. You have confirmed that the TPS is not creating a throttle plate angle voltage signal (TEST 1).
2. You have confirmed that it is getting power (TEST 2).

And in this test step you have confirmed that the throttle position sensor is getting Ground, then you can conclude that the reason its not creating a throttle plate angle signal is because it is defective and needs to be replaced.

CASE 2: The multimeter DID NOT register 12 Volts DC. This tells you that your Toyota Corolla's TPS is not getting Ground and that this is the reason why the TPS did not create a voltage signal in TEST 1.

Although it's beyond the scope of this tutorial to find the reason why this Ground is missing, you'll need to get yourself a wiring diagram (for your particular Toyota) and check the continuity of this wire between the TPS and the PCM.

1.8 Toyota Tutorials

You can find a complete list of tutorials in this index: Toyota 1.8L Index Of Articles.

• How To Test The Fuel Injectors (Toyota 1.8L).
• Diagnosing a Toyota Corolla Misfire Case Study (Toyota 1.8L).
• How To Test Engine Compression (Toyota 1.8L).
• How To Test For A Blown Head Gasket (Toyota 1.8L).