How To Test The Throttle Position Sensor (1992-1999 2.2L Toyota Celica)

The throttle position sensor, on your 2.2L Toyota Celica, creates a very simple analog voltage signal that you and I can easily test with a multimeter in Volts DC mode.

In this tutorial, I'll show you how in a step-by-step way and without using a scan tool.

As you're probably already aware, the 2.2L Celica throttle position sensor is two sensors in one assembly. One part of the TPS assembly is an idle switch and the other is the actual throttle position sensor.

In this tutorial, I'll show you how to test the TPS part of the assembly in a step-by-step way.

ES You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1992-1999 2.2L Toyota Celica) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 2.2L Toyota Celica: 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999.

IDLE SWITCH TESTS -TPS ADJUSTMENT PROCEDURE:

• TPS Idle Switch Multimeter Test (1992-1996 2.2L Toyota Camry).

Symptoms Of A Bad Throttle Position Sensor

The voltage signal, that the TPS creates, tells the fuel injection computer the exact position of the throttle plate. This information is used, among many things, to: inject more fuel, advance ignition timing, etc.

Since the TPS is such a critical role in your 2.2L Celica's engine management system, when it fails, you'll see or more of the following symptoms:

• If your 2.2L Toyota is OBD II equipped (1996+), you'll see one of the following trouble codes:
  • P0120: Throttle Position Sensor Circuit.
  • P0121: Throttle Position Sensor Circuit.
• If your 2.2L Toyota is OBD I equipped, you'll see one of the following trouble codes:
  • 41: Throttle Position Sensor Signal.
• Hesitation when accelerating the engine.
• Lack of power.
• Bad gas mileage.

Circuit Descriptions Of The TPS

The table below has a brief description of the 4 wires that make up the TPS connector.

TPS Circuits (1992-1999 2.2L Toyota Celica)
Terminal	Wire	Description
1	BRN	Sensor Ground
2	PNK (1992-1993) BLU/WHT (1994-1999)	Idle Switch Signal
3	PNK/BLK (1992-1993) BLK/WHT (1994-1999)	TPS Signal
4	PNK/BLU (1992-1993) RED (1994-1999)	5 Volts

NOTE: The above circuit descriptions apply only to the 1992-1996 2.2L Toyota Celica throttle position sensor.

Where To Buy The TPS And Save

The following links will help you to comparison shop for a new 2.2L Celica TPS. I think they'll save you a few bucks:

Not sure if the above TPS fits your particular 2.2L Toyota Celica? Don't worry, once you get to the site they'll make sure it fits by asking you the specifics of your particular Toyota vehicle. If it doesn't fit, they'll find you the right one.

TEST 1: Testing The TPS Voltage Signal

As I mentioned at the beginning of this tutorial, the TPS creates a very simple analog voltage signal that you and I can test with a multimeter. This voltage signal, which I'll call the throttle angle voltage signal, increases as the throttle plate opens.

At wide open throttle, this voltage signal maxes out at about 4.5 Volts DC. As the throttle plate is released, this voltage drops back down to its original base voltage.

To get our TPS diagnostic under way, we're gonna' check the throttle angle voltage signal increases and then decreases as we manually open and close the throttle plate.

To accomplish this, we're going to tap into the TP signal wire, which, depending on your Celica's model year, will be one of the following:

• 1992-1993 2.2L Celica —the TP signal wire is the pink with black stripe (PNK/BLK) wire of the TPS 4-wire connector.
• 1994-1999 2.2L Celica —the TP signal wire is the black with white stripe (BLK/WHT) wire of the TPS 4-wire connector.

If the TPS is bad, your multimeter will report a single value that won't increase/decrease as you open/close the throttle plate.

IMPORTANT: The TPS sensor must remain connected to its 4-wire connector during the test. To read the TP signal voltage, you'll need to either back-probe the connector or use a wire-piercing probe on the signal wire. You can see an example of this tool (the one I use), and you can also buy it here: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Here are the steps:

1. 1

   Set your multimeter to Volts DC mode.

2. 2

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

3. 3

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

4. 4

   Probe the PNK/BLK (or BLK/WHT) wire with the red multimeter test lead.
   
   This is the wire that connects to the TPS terminal labeled #3 in the illustration above.

5. 5

   Your multimeter should read between 0.2 and 0.9 Volts DC with the throttle plate closed.
   
   If it doesn't, don't worry just yet —continue with the rest of the test.

6. 6

   Slowly open the throttle by hand (from the engine compartment).
   
   The voltage should increase as the throttle opens.
   
   This increase should be smooth, without any gaps or skips.
   
   At wide open throttle, the reading should be around 3.5 to 4.5 Volts DC.

7. 7

   Slowly close the throttle.
   
   The voltage should decrease smoothly, without gaps or skips, and return to the same value you saw earlier.

8. 8

   Lightly tap on the TP sensor with the handle of a screwdriver (emphasis on lightly tap) while slowly opening and closing the throttle.
   
   If the TPS is bad, the voltage will skip or drop out.
   
   If the TPS is OK, tapping will have no effect on the voltage.

9. 9

   Repeat the throttle plate sweep test several times to confirm your results.

Let's take a look at your test results:

CASE 1: The throttle angle voltage increased and decreased as you opened and closed the throttle plate. This test result confirms that the TP sensor is OK and not defective.

CASE 2: The throttle angle voltage DID NOT increase (and/or decrease) as you opened and closed the throttle plate. This test result confirms the throttle position sensor trouble code lighting up the check engine light on your 2.2L Toyota Celica.

Our next step is to make sure that the TP sensor is getting both power and Ground. For first of these two tests, go to: TEST 2: Making Sure The TPS IS Getting Power.

CASE 3: The multimeter DID NOT register any voltage. This test result doesn't condemn the TP sensor as bad just yet.

Why? Because the TP sensor may be missing either power or Ground. So the next step is to check that the TP sensor is getting them both. For the first of these two tests, go to: TEST 2: Making Sure The TPS IS Getting Power.

TEST 2: Making Sure The TPS IS Getting Power

If you've reached this point, your TP sensor did not pass TEST 1. Before you go out and buy a new one and replace it, you need to make sure that it's getting both power and Ground.

In this test section, we're going to make sure that the TP sensor is getting power. This power comes in the form of 5 Volts and is supplied by your Toyota Celica's fuel injection computer.

Depending on the year of your Toyota Celica, this 5-Volt supply wire will be:

• 1992-1993 2.2L Celica —The wire that supplies power is a pink with blue stripe (PNK/BLU) wire of the TPS connector.
• 1994-1999 2.2L Celica —The wire that supplies power is the red (RED) wire of the TPS connector.

Once we've confirmed that the TPS is getting power, we'll move on to TEST 3 and make sure that it's getting Ground.

OK, let's begin:

1. 1

   Disconnect the TP sensor from its 4-wire connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

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

5. 5

   With the red multimeter test lead, probe the female terminal that connects to the PNK/BLU (or RED) wire.

6. 6

   Your multimeter should read 4.5 to 5 Volts DC if the TP sensor is getting power from the fuel injection computer.

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

CASE 1: Your multimeter shows 4.5 to 5 Volts DC. This confirms that the TP sensor on your Celica is getting power from the fuel injection computer.

Our next step is to make sure that the computer is also supplying the sensor with Ground. For this test, head over to: TEST 3: Making Sure The TPS IS Getting Ground.

CASE 2: The TP sensor IS NOT getting power. Double-check your test connections, make sure you're testing the correct wire, and repeat the test.

If your multimeter still doesn't show 4.5 to 5 Volts DC, then we can rule out the TP sensor itself as bad, since without power, it's not going to function.

Your next step is to find out why this 5-Volt supply is missing from the circuit and restore it. Once the TP sensor starts receiving 5 Volts from the PCM again, it will function normally.

The most likely cause of this missing 5 Volts is an open-circuit problem in the wire between the TPS connector and the fuel injection computer connector.

TEST 3: Making Sure The TPS IS Getting Ground

OK, the previous two tests have confirmed the following:

• No TP signal —The sensor isn't producing a variable voltage signal that reacts to throttle plate movement (TEST 1).
• Power present —The sensor is getting power from the fuel injection computer (TEST 2).

For our final diagnostic test, we're going to make sure that the TP sensor is getting Ground from the fuel injection computer.

This PCM-supplied Ground is only available with the key in the ON or RUN position. For our test, we'll check it with the key in the ON position and the engine OFF.

The wire that supplies this PCM-supplied Ground to the TP sensor is the brown (BRN) wire of the sensor's 4-wire connector.

To check for the presence of Ground in the BRN wire, we're going to do a simple multimeter voltage test.

CAUTION: Be careful not to apply battery power to the BRN wire, or you'll damage the fuel injection computer. The multimeter voltage test outlined below is a safe way to check for the presence of Ground in the brown wire.

These are the test steps:

1. 1

   Disconnect the TP sensor from its 4-wire connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

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

5. 5

   With the black multimeter test lead, probe the female terminal that connects to the BRN wire.

6. 6

   Your multimeter should read 10 to 12 Volts DC if the BRN wire is delivering Ground from the computer.

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

CASE 1: Your multimeter registered 10 to 12 Volts DC. This confirms that the fuel injection computer is supplying Ground to your Celica's TP sensor.

You can confidently conclude that the TP sensor is defective and needs to be replaced if the following conditions are true:

• No TP signal —The sensor isn't producing a variable voltage signal as you open or close the throttle plate (TEST 1).
• Power present —The sensor is getting 5 Volts DC from the PNK/BLU wire or the RED wire (TEST 2).
• Ground present —In this test section, you've confirmed the TP sensor is getting Ground from the computer on the BRN wire.

NOTE: You'll need to adjust the TPS assembly if you replace it. The following Toyota Camry tutorial explains the adjustment procedure: Adjusting The Throttle Position Sensor Assembly (this heading is found in the tutorial: TPS Idle Switch Multimeter Test (1992-1996 2.2L Celica)).

CASE 2: The TP sensor is not getting Ground. Double-check your test connections, make sure you're testing the correct wire, and repeat the test.

If your multimeter still doesn't register 10 to 12 Volts DC, then we can conclude that the TP sensor itself isn't bad, since without this PCM-supplied Ground, it's not going to function.

Your next step is to find out why this Ground is missing from the circuit and restore it. Once your Celica's TP sensor starts receiving Ground from the PCM again, it will function normally.

The most likely cause of this missing Ground is an open-circuit problem in the wire between the TPS connector and the fuel injection computer connector.