How To Test The Throttle Position Sensor (1996-2000 1.6L Honda Civic)

Testing the throttle position sensor (TPS) to see if it has failed and causing a TPS diagnostic trouble code (DTC) is not hard.

As a matter-o'-fact, to test the TPS on your 1.6L Honda Civic, you don't need a scan tool. In this tutorial, I'm gonna' show you how troubleshoot the throttle position sensor (TPS), on your Honda Civic, with a multimeter and in a step-by-step way.

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1996-2000 1.6L Honda Civic) (at: autotecnico-online.com).

RELATED OBD-II TROUBLE CODES:

• P0122 -What Does It Mean? (1996-2000 1.6L Honda Civic).
• P0123 -What Does It Mean? (1996-2000 1.6L Honda Civic).

Symptoms Of A Bad Throttle Position Sensor (TPS)

Your Honda Civic's PCM can't live without the input the throttle position sensor provides about throttle plate angle. So when it receives a TP signal that doesn't square with actual engine operating conditions, your Civic is just not gonna' run right.

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

1. Check engine light (CEL) shining nice and bright.
2. Diagnostic trouble codes (DTC) stored in the PCM's memory:
   • P0121: TP Sensor Circuit High Voltage.
   • P0122: TP Sensor Circuit Low Voltage.
   • P1121: TP Sensor Signal Lower Than Expected.
   • P1122: TP Sensor Signal Higher Than Expected.
3. Your Honda Civic fails the state mandated emissions test.
4. Bad gas mileage.
5. Hard start and/or extended cranking time (after shut off).
6. Black smoke coming out of the tailpipe.
7. Hesitation when accelerating your Civic.

In the next subheading we'll find out how the TPS works on your 1.6L Honda Civic.

How The Throttle Position Sensor Works

Your Civic's PCM uses several sensor inputs to control the fuel system, ignition system, and automatic transmission (to name a few). Among those sensor inputs, is the information that the throttle position sensor (TPS) provides about throttle plate angle.

As you might already be aware, the accelerator pedal is connected, via a physical cable (accelerator cable) to the throttle plate on the throttle body.

As you step on and off the accelerator pedal, the throttle plate opens and closes. It's the throttle position sensor's function to measure the amount that the throttle plate opens and closes (throttle angle). It then sends this info to the PCM (Powertrain Control Module = Fuel Injection Computer) as a volt DC signal.

To give you a few more specifics:

1. As you step on the accelerator pedal,
   • The throttle plate opens and the TP sensor measures how much and relays this to the PCM.
   • The fuel injection computer injects more fuel.
2. As you let your foot off the accelerator pedal,
   • The throttle plate closes and the TP sensor measures how much and relays this to the PCM.
   • The fuel injection computer injects less fuel.

Where To Buy Your TP Sensor And Save

The Honda service manual tells you to replace the entire throttle body when the TP sensor fails but you don't have to.

The TP sensor is sold separately and can be installed as a stand-alone part.

Where can you buy the TP sensor? You can buy it at your local auto parts store but it's gonna' cost a whole lot more. I suggest taking a look at the price of the TP sensor in the following link and compare:

Not sure the TP sensor listed fits your particular Honda? Don't worry, they'll make sure it fits your Honda, once you get to the TP sensor site, or they'll find the right one for you.

Circuit (Wire) Descriptions Of The TPS

The throttle position sensor (TPS) on your 1.6L Honda Civic is located on the side of the throttle body.

If you've already located it you can see that the TP sensor connector has 3 wires (circuits) coming out of it.

Each wire has a specific job to do. By this, I mean each wire carries a specific type of signal to or from the TPS to the PCM.

To better understand how we're gonna' test the throttle position sensor (TPS), in this tutorial, I'm going to briefly describe each wire's job and how the sensor works.

Don't worry, it's nothing too technical and it's all in plain English:

1. The TP sensor is a 3 wire sensor.
   1. Wire labeled with the number 1.
      • Feeds Ground to the TP sensor.
      • Ground is provided by the PCM (internally).
   2. Wire labeled with the number 2.
      • Feeds the throttle angle voltage signal to the PCM.
      • This voltage signal varies depending on the amount of throttle plate opening.
   3. Wire labeled with the number 3.
      • Feeds power to the TP sensor.
      • In the form of 5 Volts DC and is supplied only with Key On Engine Off (KOEO) or Key On Engine Running (KOER).
      • Power comes directly from the PCM.
2. The TP sensor is a potentiometer. Its resistance changes in response to changes in the throttle plate's angle.
   1. With throttle closed, a small voltage is create and sent to the PCM.
      • At closed throttle the TP sensor outputs about 0.5 Volts DC.
   2. With throttle open to wide open, a bigger voltage is created and sent to the PCM.
      • At wide open throttle the TP sensor outputs about 4.5 Volts DC.

REMEMBER: The throttle position sensor (TPS), at closed throttle, produces a low voltage signal of around 0.5 Volts DC. As the throttle plate starts to open (as you step on the accelerator pedal and accelerate the engine), this 0.5 Volt signal starts to increase. At wide open throttle, the TP sensor will output about 4.5 Volts DC.

With this bit of information, let's move on to the next subheading.