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.
The contents of this tutorial at a glance:
- Symptoms of a Bad Throttle Position Sensor.
- TEST 1: Testing the TPS Voltage Signal.
- TEST 2: Verifying Throttle Position Sensor Has 5 Volts and Ground.
- Where to Buy Your Throttle Position Sensor and Save.
NOTE: This tutorial applies to the 1992 thru' 1999 2.2L Toyota Celica only.
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1992-1999 2.2L Toyota Celica) (at: autotecnico-online.com).
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.
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)|
|Idle Switch Signal|
NOTE: The above circuit descriptions apply only to the 1992-1996 2.2L Toyota Celica throttle position sensor.
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.
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: You don't need to remove the TPS to bench test it, since the instructions below are for an on-car test. Since the TPS needs to remain connected to its connector, you'll need to use a back-probe or a wire-piercing probe to measure the TP signal voltage.
NOTE: On the 1992-1993 2.2L Celica, you'll be testing the pink with black stripe (PNK/BLK) wire of the TPS connector. On the 1994-1999 2.2L Celica, you'll be testing the black with white stripe (BLK/WHT) wire of the TPS connector.
Here are the steps:
Turn the key to the ON position but don't start the engine, and place your multimeter in Volts DC mode.
Probe the PNK/BLK (or BLK/WHT) wire with the RED multimeter lead. This is the wire that connects to TPS male spade terminal identified with the #3 in the illustration above.
Ground the BLACK multimeter test lead on the battery negative terminal.
Your multimeter should report a voltage between .2 to .9 Volts DC with the throttle plate closed. If your multimeter doesn't, don't worry about it just yet, continue with the other steps.
Slowly open the throttle (by hand and from the engine compartment). The voltage numbers should increase as the throttle plate opens.
This increase in voltage should be smooth and without any gaps or skips. Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC.
Slowly close the throttle. As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 3.
Lightly tap on the throttle position sensor with the handle of a screw-driver (or something similar, and I want to emphasize the words ‘lightly tap’) as you slowly open and close the throttle and observe the multimeter.
If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers.
Repeat step 6 several times to make sure of your multimeter test 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.
If I where in your shoes and to be sure that the TPS has truly failed, I would still make sure that the TP sensor is getting both power and ground. For these tests, go to: TEST 2: Verifying Throttle Position Sensor Has 5 Volts and Ground.
CASE 3: 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, go to TEST 2: Verifying Throttle Position Sensor Has 5 Volts and Ground.