In this tutorial, I'll show you how to test the throttle position sensor (TPS) using just a multimeter. With your test results, you'll be able to easily diagnose any of the TP sensor trouble codes that might be lighting up your check engine light (CEL).
- P0120: Throttle Position Sensor (TPS) Circuit.
- P0121: Throttle Position (TP) Sensor Circuit/Range Performance.
- P0122: Throttle Position (TP) Sensor Voltage High.
- P0123: Throttle Position (TP) Sensor Voltage Low.
The whole testing process is explained in an easy, step-by-step manner. You'll quickly find out whether your TPS is good or bad, and the best part is, you don't need an expensive scan tool to get the job done.
I'll also cover some of common issues that can affect engine performance when the TPS fails, and I'll even let you know where to buy a replacement if needed.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1995-2000 2.0L Dodge Stratus, Plymouth Breeze) (at: autotecnico-online.com).
APPLIES TO: Applies to the following vehicles:
- 2.0L Dodge Stratus: 1995, 1996, 1997, 1998, 1999, 2000.
- 2.0L Plymouth Breeze: 1996, 1997, 1998, 1999, 2000.
What Does The TPS Sensor Do?
The Throttle Position Sensor (TPS) is a critical component in your car's engine management system. It's a potentiometer that sends information to the fuel injection computer about the position of the throttle. In simpler terms, it tells the computer how far you're pressing the gas pedal.
Here's how the TPS impacts your vehicle's operation:
- Fuel Efficiency: The sensor helps the fuel injection computer figure out the optimal air-fuel mix for your engine, contributing to better fuel economy.
- Engine Performance: By knowing the throttle position, the fuel injection computer can adjust ignition timing and fuel injection, which helps your car perform smoothly whether you're idling or speeding down the highway.
- Transmission Control: In automatic models, the TPS can influence when the car shifts gears, ensuring smoother driving.
Here's how it works in a nutshell:
- The sensor gets a constant 5-volt reference signal and Ground from your vehicle's fuel injection computer.
- When the throttle plate is closed (like when you're not pressing the gas pedal), the TPS sends a low voltage signal back to the computer.
- As you press the gas pedal, the throttle plate opens, turning the sensor. This changes the resistance in its potentiometer.
- The change in resistance modifies the voltage signal. So as the throttle plate opens, the voltage increases; when it closes, the voltage decreases.
- The computer reads this voltage to understand the throttle position and adjusts air/fuel mixture, ignition timing, and other things to make your Stratus (Breeze) run smoothly.
Symptoms Of A Bad TPS
When the TPS fails, you'll likely notice a few signs that something's off. Here are some common symptoms:
- Poor Acceleration: Your Stratus (Breeze) may hesitate or stumble when you hit the gas pedal.
- Rough Idling: The engine may sputter or shake when your car is in idle.
- High or Erratic RPMs: The engine's RPM might shoot up unexpectedly, even when you're not pressing the gas pedal.
- Bad Fuel Economy: Your car might start guzzling gas more than usual.
- Stalling: In extreme cases, the car might stall, especially when coming to a stop or at low speeds.
- Check Engine Light: The Check Engine Light (CEL) will come on, and one of the following trouble codes will be registered in the fuel injection computer's memory:
- P0120: Throttle Position Sensor (TPS) Circuit.
- P0121: Throttle Position (TP) Sensor Circuit/Range Performance.
- P0122: Throttle Position (TP) Sensor Voltage High.
- P0123: Throttle Position (TP) Sensor Voltage Low.
- Transmission Issues: If you have an automatic transmission, you might experience hard or erratic shifting.
- Unresponsive Throttle: Sometimes, the throttle might feel less responsive or even unresponsive, making driving difficult.
Throttle Position Sensor (TPS) Circuits And Pinout
NOTE: The illustration of the TPS connector in this tutorial shows the front view of the connector (female terminal view).
| TPS Connector Pinout | ||
|---|---|---|
| Pin | Wire Color | Description |
| 1 | BLK/LT BLU | Sensor Ground |
| 2 | ORG/DK BLU | Throttle Position Signal |
| 3 | VIO/WHT | 5 Volts |
Where To Buy The TPS And Save
You can buy the throttle position sensor for your 2.0L Stratus (Breeze) in just about any auto parts store but you'll spend a whole lot more because they mark it up quite a bit.
My suggestion is to buy it online or at least comparison shop to get an idea of how much it costs and how much you can save.
The following links:
TEST 1: Checking The Throttle Position Sensor (TPS) Signal
We'll begin our test by focusing on checking the TPS output voltage signal with a multimeter set to to Volts DC mode. You'll to tap into the orange with dark blue stripe (ORG/DK BLU) wire, as this is the TPS signal wire.
The TPS must remain connected to its connector during the test. So to tap into the TPS signal wire, you'll need a special tool: either a back-probe or a wire-piercing probe to access the signal.
If the sensor is OK, you should see the voltage signal increase as you open the throttle and decrease as you close it. It's a pretty simple, and you'll know right off the bat if there's an issue with the TPS on your Stratus (Breeze).
IMPORTANT: This is an on car test of the sensor and the throttle position sensor must remain connected to its harness connector.
Here are the test steps:
- 1
Set your multimeter to its DC Volts function.
- 2
Connect the black probe of the multimeter directly to the negative (-) terminal of the battery.
- 3
Turn the key to the RUN position but don't crank or start the engine.
- 4
Connect the red probe to the ORG/DK BLU wire of the TPS sensor connector.
The ORG/DK BLU wire connects to the terminal labeled with the number 2 in the connector illustration above.
NOTE: The TPS sensor should be connected to its connector, so you'll need to use a back probe on the backside of the connector or use a wire piercing probe to reach the signal within the wire (to see an example of this tool and where to buy it: Wire Piercing Probe). - 5
Your multimeter should read a voltage between 0.3 and 1.0 Volts DC with the throttle closed.
- 6
Manually open the throttle.
NOTE: You'll get the best results by opening and closing the throttle directly at the throttle body instead of stepping on the gas pedal. - 7
The multimeter should display a voltage that increases as you (or your helper) open the throttle.
With the throttle fully open, your multimeter should read: 3.2 to 4.9 Volts DC. - 8
Slowly close the throttle.
- 9
The multimeter should display a voltage that decreases as you start to close the throttle.
- 10
Using the handle of a screwdriver, lightly tap the TPS sensor while you open and close the throttle and watch the multimeter.
The purpose (of tapping the TPS sensor with the screwdriver handle) is to see if the TPS sensor shows any gaps in the voltage signal. Why? Because a good TPS sensor will show a voltage signal that continually increases or decreases even as the screwdriver handle taps it.
Alright, let's examine your test results:
CASE 1: The TP sensor signal's voltage increased and decreased smoothly and without gaps. This test result confirms that the throttle position sensor (TPS) is OK and not defective.
This test result also tells you that the TPS sensor is getting 5 Volts and Ground from the fuel injection computer.
CASE 2: The TP sensor signal's voltage did not increase or decrease. Most of the time, this test result tells you that the TPS sensor is bad. But not always.
To be really sure the TPS is bad, you need to make sure that it's getting 5 Volts and Ground. Your next step is to go to: TEST 2: Making Sure The TPS Is Getting Power.
CASE 3: The TP sensor signal's voltage showed gaps in its voltage output as you tapped the sensor with the screwdriver. This test result tells you the TPS is bad and needs to be replaced.
