How To Test The Throttle Position Sensor (1995-2000 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.

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

APPLIES TO: This tutorial applies to the following vehicles:

• 1.6L Honda Civic CX: 1995, 1996, 1997, 1998, 1999, 2000.
• 1.6L Honda Civic DX: 1995, 1996, 1997, 1998, 1999, 2000.
• 1.6L Honda Civic EX: 1995, 1996, 1997, 1998, 1999, 2000.
• 1.6L Honda Civic LX: 1995, 1996, 1997, 1998, 1999, 2000.
• 1.6L Honda Civic Del Sol: 1996, 1997.

Wiring Diagrams: The following TPS circuit wiring diagrams may come in handy:

• TPS Sensor Circuit Wiring Diagram (1995 1.6L Honda Civic).
• TPS Sensor Circuit Wiring Diagram (1996 1.6L Honda Civic).
• TPS Sensor Circuit Diagram (1997-1998 1.6L Honda Civic).
• TPS Sensor Circuit Diagram (1999-2000 1.6L Honda Civic).

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 Volts 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.

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.
   • Wire labeled with the number 1.
     • Feeds Ground to the TP sensor.
     • Ground is provided by the PCM (internally).
   • 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.
   • 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.
   • 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.
   • 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.

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:

NOTE: 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.

TPS TEST 1: Testing The TPS Voltage Signal

The key to diagnosing the your Honda Civic's throttle position sensor (TPS) is to remember that:

1. The TP sensor's voltage signal increases when the throttle plate opens.
2. The TP sensor's voltage decreases when the throttle plate closes.

Using a multimeter, we're gonna' tap into the sensor's middle wire (which is the TP signal wire) and see if the TP sensor can create and report a variable voltage signal.

Once we're tapped into this circuit, we'll manually rotate the throttle to its opened and closed positions and see if our multimeter now records the TP signal voltage increasing and decreasing.

I'll explain everything in a step-by-step manner in the following instructions.

NOTE: The throttle position sensor has to remain connected during the TP signal test. You'll need to use a back probe on the connector or a wiring piercing probe on the wire. This is the tool I use and recommend: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

You can see this test step performed in this YouTube video here: How To Test The TPS (1997, 1998, 1999, 2000, 2001 2.0L Honda CR-V)   (NOTE: Although this video applies to the 1997-2001 2.0L Honda CR-V, the test procedure itself is the same for the 1996-2000 1.6L Honda Civic).

OK, let's start:

Part 1

1. 1

   Set your multimeter to Volts DC mode.

2. 2

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

3. 3

   Connect the red multimeter test lead to the middle wire of the sensor's connector.
   
   NOTE: The TP sensor must remain connected to its 3-wire connector to read the TP signal.

4. 4

   Have your helper turn the key to the ON position, but don't start the engine (this will power up the TP sensor).

5. 5

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

Part 2

1. 6

   Now, slowly open the throttle plate (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.
   
   For this test result to be accurate, you need to open the throttle by hand and not from inside the vehicle.

2. 7

   As the throttle plate opens, the voltage numbers will increase.
   
   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

   Now, slowly close the throttle plate.
   
   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 5.

Part 3

1. 9

   Have your helper 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.

2. 10

   Repeat step 9 several times to make sure of your multimeter test results.

Let's take a look at your test results:

CASE 1: The multimeter registered a smooth increase or decrease in voltage with no glitches. This is the correct and expected test result. In other words, the TP sensor passed with flying colors.

This test result also let's you know that the problem causing the P1121 trouble code is intermittent and not present at this point in time.

CASE 2: The voltage increased and decreased but glitched out when tapping the sensor. This tells you that the TP sensor is bad. Replace the throttle position sensor.

When you're ready to replace the TP sensor, take a look at the following sensors. They're from known automotive brands I've used my entire auto repair career:

• Dorman 911-753 Throttle Position Sensor (Amazon affiliate link).

CASE 3: The TP signal voltage stayed stuck in one value as you opened and closed the throttle. This usually means the TP sensor is toast.

To be absolutely sure the sensor is bad, our next step is to check that the TPS is getting power, for this test go to: TPS TEST 2: Verifying TPS Has Power.

CASE 4: The multimeter DID NOT register any voltage. This test result doesn't condemn the TPS as bad just yet. Why? Because the TPS may be missing either power or Ground.

The next step is to check that the TPS is getting power, for this test go to: TPS TEST 2: Verifying TPS Has Power.

TPS TEST 2: Verifying TPS Has Power

The wire (circuit) labeled with the number 3 in the illustration is the one that feeds the TP sensor with power.

As stated earlier, this power is in the form of 5 Volts DC and is feed to the TP sensor by the PCM.

If your TP sensor did not show a variable voltage when you manually actuated the throttle in TPS TEST 1, then there's a good chance it's not being fed with power.

In this test section, we'll test for the presence of these 5 Volts using a multimeter.

IMPORTANT Be careful with probing the front of the TPS connector female terminals. If the terminal gets damaged, you'll have to replace the connector.

You can see this test step performed in this YouTube video here: How To Test The TPS (1997, 1998, 1999, 2000, 2001 2.0L Honda CR-V)   (NOTE: Although this video applies to the 1997-2001 2.0L Honda CR-V, the test procedure itself is the same for the 1996-2000 1.6L Honda Civic).

This is what you'll need to do:

1. 1

   Disconnect the TP sensor from its 3-wire connector.

2. 2

   Set your trusty multimeter's dial to Volts DC mode.

3. 3

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

4. 4

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

5. 5

   Gently probe the female terminal 3 with the red multimeter test lead.

6. 6

   Your multimeter should display 4.5 to 5 Volts on its screen.

OK, this what your reading tells you:

CASE 1: The multimeter registered 4.5 to 5 Volts. This confirms that the TP sensor is being fed with power (4.5 to 5 Volts DC).

The next step is to test the Ground circuit of the throttle position sensor, go to: TPS TEST 3: Verifying TPS Has Ground.

CASE 2: Multimeter DID NOT register 4.5 to 5 Volts. Without this voltage the TP sensor will not function. The two most likely reasons for this are: 1) an open in the circuit (wire) or 2) the PCM may be fried (although a bad PCM is very rare).

Although it's beyond the scope of this article to test these two conditions, you have now eliminated the throttle position sensor (TPS) on your Honda as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TPS TEST 3: Verifying TPS Has Ground

So far (if you've started from TEST 1) you've confirmed that the TP sensor isn't creating a variable signal and that it's getting power.

Now, we're gonna' check to see if it's getting Ground.

This Ground is provided by the wire labeled with the number 1, in the illustration in the image viewer.

IMPORTANT: Remember, the PCM is the one that provides this Ground internally so be careful and don't accidentally or intentionally apply power (12 Volts) to this circuit or you'll fry the PCM.

You can see this test step performed in this YouTube video here: How To Test The TPS (1997, 1998, 1999, 2000, 2001 2.0L Honda CR-V)   (NOTE: Although this video applies to the 1997-2001 2.0L Honda CR-V, the test procedure itself is the same for the 1996-2000 1.6L Honda Civic).

OK, here are the test steps:

1. 1

   Disconnect the TP sensor from its 3-wire connector.

2. 2

   Set the multimeter to Volts DC mode.

3. 3

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

4. 4

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

5. 5

   Gently probe the female terminal 1 with the black multimeter test lead.

6. 6

   Your multimeter should display 10 to 12 Volts on its screen.

Let's take a look at your test results:

CASE 1: The multimeter showed 10 to 12 Volts. This confirms that the PCM and the wire/circuit (that supply this Ground) are OK.

You can conclude the TP sensor is toast and needs to be replaced if all three test have confirmed that:

1. The TPS is not providing a varying voltage signal when manually opening the throttle plate (TEST 1).
2. The TPS is being fed 5 Volts DC (TEST 2).
3. The TPS is being fed Ground (this test section).

When you're ready to swap it out, these are the two sensors I recommend from two known automotive brands I don't hesitate to recommend:

• Dorman 911-753 Throttle Position Sensor (Amazon affiliate link).
• APDTY 022864 Throttle Body Position Sensor (Amazon affiliate link).

CASE 2: Multimeter DID NOT show 10 to 12 Volts. This usually indicates a problem with either the PCM (internal fault/problem) or an open in the wire between the TPS and the PCM itself.

Although testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your Honda as being the cause of the problem and/or the TPS Diagnostic Trouble Code (DTC) lighting up the check engine light (CEL).

More 1.6L Honda Civic Test Tutorials

If this tutorial was helpful/informative, you can find a complete list of tutorials in this index:

• 1.6L Honda Civic Index Of Articles

Here's a sample of the tutorials you'll find there:

• How To Test For A Blown Head Gasket (1995-2000 1.6L Honda Civic).
• How To Test The Alternator (1996-2000 1.6L Honda Civic).
• Testing Shift Control Solenoid Valves A and B (1996-2000 1.6L Honda Civic).
• How To Troubleshoot A No Start (1995-2000 1.6L Honda Civic).
• How To Test The Igniter, Ignition Coil Accord, Civic, CRV, and Odyssey (at: easyautodiagnostics.com).