How To Test The TPS (1992-1997 2.2L Beretta, Cavalier, Corsica, Sunfire)

You can easily and accurately test the throttle position sensor with a multimeter, and in this tutorial, I'll explain how to step by step.

With the test results of your TPS multimeter test, you'll quickly determine if the throttle position sensor is good or bad.

You'll also be able to diagnose the following TPS diagnostic trouble codes: codes 21 and 22 (OBD I) and P0121, P0122, and P0123 (OBD II).

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1992-1997 2.2L Beretta, Cavalier, Corsica, Sunfire) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 2.2L Chevrolet Beretta: 1992, 1993, 1994, 1995, 1996.
• 2.2L Chevrolet Cavalier: 1992, 1993, 1994, 1995, 1996, 1997.
• 2.2L Chevrolet Corsica: 1992, 1993, 1994, 1995, 1996.
• 2.2L Pontiac Sunfire: 1995, 1996, 1997.

Symptoms Of A Bad Throttle Position Sensor

The accelerator pedal connects to the throttle plate (in the throttle body) with an accelerator cable.

So when you step on or off the accelerator pedal, the throttle plate opens/closes.

The throttle position sensor's job is to measure how much the throttle plate opens (or closes) as you step on or off the accelerator pedal.

Since the fuel injection computer constantly monitors the throttle position sensor, when it fails, you'll see one of the following TPS diagnostic trouble codes illuminating the check engine light :

OBD I equipped vehicles:

• 21: Throttle Position Sensor (TPS) Signal Voltage High.
• 22: Throttle Position Sensor (TPS) Signal Voltage Low.

OBD II equipped vehicles:

• P0121: Throttle Position (TP) Circuit Performance Problem.
• P0122: Throttle Position (TP) Circuit Low Input.
• P0123: Throttle Position (TP) Circuit High Input.

You'll also see one or more of the following symptoms:

• Hesitation when accelerating the engine.
• Lack of power.
• Bad gas mileage.

Where To Buy The TPS And Save

The following links will help you comparison shop for the throttle position sensor of known automotive brands (no knock-off TPS sensors):

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

TEST 1: Testing The TPS Voltage Signal

When testing the TPS, it's essential to know that the throttle position sensor creates a voltage signal that increases as the throttle plate opens and decreases as the throttle plate closes.

In this first test section, you'll connect your multimeter to the TPS signal wire and check that its voltage signal increases/decreases as you manually open/close the throttle plate.

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

The wire that you'll connect your multimeter to is the blue wire of the sensor's three-wire connector. I've labeled it with the letter C in the photo above.

NOTE: You'll need a multimeter to be able to test the throttle position sensor. If you don't have one, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.

OK, let's start:

PART 1:

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

   Connect the red multimeter test lead to the blue (BLU) wire of the TP sensor harness connector.
   
   The BLU wire is identified with the letter C in the photo above.

4. 4

   Connect the black multimeter test lead to the battery negative (-) terminal.
   
   NOTE: The TP sensor must remain connected to its electrical connector. You'll need to use a back probe or a wiring piercing probe to tap into the signal of the middle wire. To see what a wire piercing probe looks like and where to buy one, go here: Wire Piercing Probe.

5. 5

   Your multimeter should report a voltage between 0.2 to 0.9 Volts DC with the throttle plate closed.
   
   If your multimeter doesn't, don't worry about it just yet, continue with the other steps.

PART 2:

1. 6

   Slowly open the throttle plate (by hand from the engine compartment).

2. 7

   The voltage value 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.

3. 8

   Slowly close the throttle plate.

4. 9

   As the throttle plate is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the same voltage you noticed in step 3.

5. 10

   Lightly tap on the throttle position sensor with the handle of a screw-driver or something similar (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.

6. 11

   Repeat step 7 several times to make sure of your multimeter test results.

Let's take a look at your test results:

CASE 1: The TPS signal voltage increased/decreased as you opened/closed the throttle plate. This is the correct test result and it lets you know the TPS is functioning correctly.

You can also conclude that the TPS is receiving power and Ground. No further testing is needed.

CASE 2: The TPS signal voltage DID NOT increase/decrease as you opened/closed the throttle plate. This test result usually tells you the TPS is bad.

To be sure the TPS is bad, you need to make sure it's getting power and Ground. Go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.

CASE 3: The multimeter DID NOT register any voltage. This test result usually means the TPS is bad.

To be sure the TPS is bad, you need to make sure it's getting power and Ground. Go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.