How To Test The Throttle Position Sensor (1993-1997 1.8L Toyota Corolla)

TEST 2: Verifying Throttle Position Sensor Has Power

Chances are, the reason you got a signal performance issue in TEST 1 is that the TPS isn't receiving power.

Your Corolla's throttle position sensor needs 5 Volts DC from the fuel injection computer to get powered and generate its voltage signal.

The wire responsible for delivering this voltage connects to terminal 4 of the TPS engine wiring harness connector (see the diagram above).

Alright, let's get this test started:

1. 1

   Set your multimeter to Volts DC mode.

2. 2

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

3. 3

   Disconnect the TPS from its 4-wire connector.

4. 4

   Turn the key to the ON position without starting the engine.
   
   This powers up the TP sensor's connector.

5. 5

   Use the red multimeter test lead to probe the TPS connector female terminal 4.
   
   IMPORTANT: Be careful when testing the female metal terminal on the TPS connector. The multimeter test probe could damage it and then you'll have to replace the connector.

6. 6

   Your multimeter should read between 4.5 and 5 Volts.

Let's break down what your test results mean:

CASE 1: Your multimeter showed a reading between 4.5 and 5 Volts. This confirms that the throttle position sensor (TPS) is receiving power from the fuel injection computer.

The next (and final) step is checking whether the TPS is also getting Ground from the PCM. To do that, head over to: TEST 3: Verifying Throttle Position Sensor Has Ground.

CASE 2: Your multimeter didn't show 4.5 to 5 Volts. Double-check your connections and run the test again.

If your multimeter still doesn't detect 4.5 to 5 Volts DC, that means the TPS itself isn't the problem. Without power, it can't send a throttle angle voltage signal and the reason why you're getting a TPS trouble code.

Your next step is to find out why this voltage is missing and restore them to the circuit.

TEST 3: Verifying Throttle Position Sensor Has Ground

For this final test, we're gonna make sure the throttle position sensor is getting Ground.

Your Corolla's fuel injection computer provides this Ground. The wire delivering it connects to terminal 1 of the TPS engine wiring harness 4-wire connector (see the connector illustration above).

IMPORTANT: Be extra careful checking for Ground in this circuit —don't accidentally or intentionally short this circuit to battery voltage, or you'll end up frying your Corolla's fuel injection computer.

Here's how to run the test:

1. 1

   Switch your multimeter to Volts DC mode.

2. 2

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

3. 3

   Turn the key to the ON position, but don't start the engine. This powers up the fuel injection computer.

4. 4

   Use the black multimeter test lead to probe the TPS connector female terminal 1.
   
   NOTE: Be careful not to damage the female terminal when probing it with the multimeter test lead.

5. 5

   If the BLK wire is supplying Ground to the TPS, your multimeter should read between 10 and 12 Volts.

Let's break down what your test results mean:

CASE 1: Your multimeter displayed 10 to 12 Volts. That confirms the throttle position sensor (TPS) on your Toyota is getting Ground from the computer.

You can conclude that the TPS is bad and needs to be replaced if you have confirmed:

1. The TP sensor isn't generating a changing voltage signal when you manually open the throttle plate (TEST 1).
2. The TP sensor is receiving 5 Volts DC (TEST 2).
3. The TP sensor is getting Ground (this test section).

After installing the new TPS, you'll need to adjust it properly. You can find the steps in this tutorial:

• TPS Idle Switch Multimeter Test (1.8L Toyota Corolla).

CASE 2: The multimeter didn't show 10 to 12 Volts. Double-check that you're testing the right terminal on the connector and try again.

If the voltage still doesn't appear, that means there's likely an open-circuit between the TP sensor harness connector and the fuel injection computer's harness connector. In rare cases, the computer itself might have an internal issue.

Although diagnosing these two possibilities is outside the scope of this tutorial, you now know that the throttle position sensor (TPS) on your 1.8L Toyota isn't the root of the problem or the reason for the TPS trouble code triggering the check engine light.

More 1.8L Toyota Corolla Tutorials

There are several more 'how to' tutorials that I've written that are 1.8L Toyota Corolla specific, that may be of further help. You can find them here:

• 1.8L Toyota Corolla Index Of Articles.

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

• How To Test Engine Compression (1993-2008 1.8L Toyota Corolla).
• How To Test For A Blown Head Gasket (1993-2008 1.8L Toyota Corolla).
• Misfire Codes: How To Troubleshoot And Repair Them (1996-2008 1.8L Toyota Corolla).
• How To Test The Fuel Injectors (1993-1997 1.8L Toyota Corolla).