How To Test The TPS With A Multimeter (1993-1995 3.0L V6 Nissan Quest)

The throttle position sensor (TPS) on the 1993-1995 3.0L V6 Nissan Quest or Mercury Villager is really two components in one. One part is the throttle position sensor and the other is an idle switch.

In this tutorial, I'm going to show you how to test the throttle position sensor part of the TPS assembly with a multimeter.

All of the steps are explained in a step-by-step manner so you can quickly and easily figure out if the TPS is toast and needs to be replaced.

I'll also point you to the tutorial that shows you how to correctly adjust the sensor if you've replaced it, need to replace it, or if it's out of adjustment.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 Nissan Quest: 1993, 1994, 1995.
• 3.0L V6 Mercury Villager: 1993, 1994, 1995.

IDLE SWITCH TESTS:

• How To Test And Adjust The Idle Switch (1993-1995 3.0L V6 Nissan Quest).

TPS/IDLE SWITCH CIRCUIT DIAGRAM:

• TPS And Idle Switch Circuit Wiring Diagram (1993-1995 3.0L V6 Nissan Quest).

Symptoms Of A Bad Throttle Position Sensor

The powertrain control module (PCM) in your Nissan Quest or Mercury Villager needs to know how much you're stepping on, or stepping off, the accelerator pedal. That's because the gas pedal is connected to the throttle plate by a mechanical cable.

As you step on the gas pedal, the throttle plate opens to allow more air into the engine, and when you step off the pedal, the throttle plate closes and the amount of air entering the engine decreases.

Because the TPS is a critical part of the engine management system, when it fails, you're going to see one or more of the following engine performance issues:

• Hesitation when you tip into the throttle —You step on the gas and it seems like the engine "falls on its face" for a moment before power kicks in.
• Poor acceleration/weak power —You step on the gas pedal and the engine feels lazy, especially if you're pulling away from a stop or merging.
• Rough idle —The engine's idle isn't steady (may hunt up and down). You can feel the engine "shaky" especially at a stop light.
• Stalling (often at idle or when coming to a stop) —The engine may die when you let off the gas or when you shift into gear.
• Erratic throttle response —Throttle response feels inconsistent. In other words, stepping on the accelerator pedal doesn't always give you the same engine/power response.
• Weird/harsh/late automatic transmission shifting —Because the automatic transmission uses throttle angle/load info, a bad TPS signal can cause odd shift timing/feel.
• Check Engine Light (or stored fault code) —The ECU/PCM can flag the TPS circuit/signal as out of range.
  • Code 43: Throttle Position Sensor

Throttle Position Sensor Circuit Descriptions

The TPS sensor assembly on your 1993-1995 Nissan Quest (or Mercury Villager) has two electrical connections.

One connector is built directly into the TPS assembly and is used by the throttle switch portion of the sensor.

The second connection is a 3-wire connector that plugs into three wires coming out of the TPS assembly. This 3-wire connector belongs to the throttle position sensor (TPS) portion of the assembly, and this is the connector we'll be testing in this tutorial.

Here's a brief description of the 3 TPS circuits (wires):

Terminal	Wire	Description
4	Brown (BRN)	5V Input
5	Red (RED)	TPS Signal Output
6	White with black stripe (WHT/BLK)	Sensor Ground Input

Where To Buy Your TPS/Idle Switch Sensor And Save

Where can you buy the TP sensor for your 3.0L Nissan Quest? 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 links and compare:

Not sure if the above TP sensor fits your particular 3.0L Nissan Quest or Mercury Villager? Don't worry, once you get to the site, they'll make sure it fits by asking you the particulars of your vehicle. If it doesn't fit, they'll find you the right one.

TEST 1: Testing The TPS Voltage Signal

To begin our throttle position sensor diagnostic, we're going to tap into the TPS signal wire with a multimeter and check to see if the throttle position sensor is actually producing an usable TPS voltage signal.

If the TPS sensor is OK, you should see the following:

1. As the throttle plate opens, the TPS signal voltage increases.
2. As the throttle plate closes, the TPS signal voltage decreases.

If the TPS sensor is toast, you'll generally see the output voltage stay stuck at one value, regardless of how much you open or close the throttle plate.

Before we begin, I want to point out two important things:

• First, we're going to be testing the red (RED) wire of the engine wiring harness connector. This connector plugs into the 3-wire connector of the throttle position sensor assembly.
• Second, the TPS sensor must remain connected to its connector during the test.

To read the TPS signal on the RED wire, you'll need to backprobe the connector or use a wire-piercing probe on the wire itself. My go-to method is a wire-piercing probe. If you don't have one and need to buy one, this is the one I use and recommend: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Here are the steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Connect the red multimeter test lead to the RED wire of the sensor's 3-wire connector.
   
   The RED wire connects to the terminal labeled with the number 5 in the illustration above.
   
   NOTE: Make your connections on the wire of the engine wiring harness connector, not on the wire coming out of the TPS sensor assembly itself. Also, all connectors must remain connected to each other during the test.

3. 3

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

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

   Slowly open the throttle (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.
   
   As the throttle opens, the voltage numbers should increase.
   
   Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC.
   
   NOTE: For this test result to be accurate, you need to open the throttle by hand and not from inside the vehicle.

2. 7

   Slowly close the throttle.
   
   As the throttle plate closes, the voltage numbers should decrease to the exact same voltage you noticed in step 5.

Part 3

1. 8

   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 glitch out (skip or go blank). If the TPS is OK, the tapping will have no effect on the voltage numbers.

2. 9

   Repeat step 8 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 and decreased as you opened and closed the throttle plate. This is the correct and expected result and tells you that your Nissan Quest or Mercury Villager's TPS is doing its job and isn't defective.

If you still suspect a TPS problem, or you've got a Code 43 lighting up the Check Engine Light, there's a good chance the sensor assembly is simply out of adjustment. To check the sensor's adjustment, see this tutorial: LINK GOES HERE.

CASE 2: The TPS signal voltage did not increase or decrease as you opened and closed the throttle plate. This result generally indicates that the throttle position sensor portion of the TPS assembly is toast.

Before replacing the TPS sensor assembly, we need to make sure the sensor itself is getting both 5 Volts and Ground from the PCM. For the first of those two checks, head over to: TEST 2: Making Sure The TPS Is Getting 5 Volts.

CASE 3: The multimeter did not register any voltage at all as you opened and closed the throttle plate. This usually means the TPS assembly isn't getting power or Ground from the PCM, although a bad sensor is still a possibility.

To find out which one it is, your next step is to go to make sure the TPS is getting its 5-Volt reference signal. Go to: TEST 2: Making Sure The TPS Is Getting 5 Volts.

TEST 2: Making Sure The TPS Is Getting 5 Volts

Like any other electrical component, the throttle position sensor needs power and Ground to be able to generate its output voltage signal. Now that you've confirmed the TPS signal is either missing or stuck —regardless of how much you open or close the throttle plate— in this test section, we're going to make sure the sensor is getting its 5 Volts.

These 5 Volts come from your minivan's powertrain control module (PCM) and are delivered by brown (BRN) wire of the engine wiring harness connector.

The BRN wire connects to terminal 5 of the TPS 3-wire connector (see illustration above). These 5 Volts are present with the key in the START or RUN position.

For our testing purposes, we're going to check for the presence of these 5 Volts with the key in the RUN position, but with the engine OFF.

Alright, let's get started.

1. 1

   Select Volts DC mode on your multimeter.

2. 2

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

3. 3

   Disconnect the engine wiring harness connector from the TP sensor assembly's 3-wire connector.

4. 4

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

5. 5

   With the red multimeter test lead probe the female terminal that connects to the BRN wire of the engine wiring harness connector.
   
   NOTE: Gently probe the female terminal with your multimeter test lead to avoid damaging it.

6. 6

   The multimeter should report 4.5 to 5 Volts DC.

Let's take a look at what your test results mean:

CASE 1: The BRN wire is delivering 5 Volts DC. So far, so good, since this is the correct and expected test result.

Our next step is to move on to the next test section and make sure the sensor is getting Ground. Go to: TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: The BRN wire isn't delivering 5 Volts DC. First, double-check that you're testing the correct female terminal of the engine wiring harness connector. Make sure that terminal actually connects to the BRN wire, then repeat the test.

If you still don't see 5 Volts, you can rule out the throttle position sensor itself as the cause of the Code 43 lighting up the check engine light on your minivan. Without those 5 Volts, the TPS simply can't produce a signal that the PCM can use.

Although it's beyond the scope of this tutorial, your next step is to find out why this voltage is missing and restore it to the circuit. Once the BRN wire delivers 5 Volts to the sensor, the Code 43 will clear and the engine performance issues will go away.

The most likely cause of this missing voltage is an open-circuit between the TPS connector and the PCM.

TEST 3: Making Sure The TPS Is Getting Ground

If you've reached this point, you've already confirmed the following two conditions:

1. The TPS signal voltage is either missing or stuck at one value as you open and close the throttle plate (TEST 1).
2. The BRN wire of the engine wiring harness connector is delivering 5 Volts to the TPS sensor (TEST 2).

For our final diagnostic test, we're going to make sure the throttle position sensor is getting Ground, which comes directly from your minivan's PCM.

The wire that delivers this PCM-supplied Ground is the white with a black stripe (WHT/BLK) wire in the engine wiring harness connector that plugs into the TPS's 3-wire connector. This Ground is only available with the key in the RUN or START position.

For this test, we'll check it with the key in the RUN position, but with the engine OFF with and by doing a simple multimeter voltage test (with the multimeter set to Volts DC).

Alright, here are the test steps.

1. 1

   Select Volts DC mode on your multimeter.

2. 2

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

3. 3

   Disconnect the engine wiring harness connector from the TP sensor assembly's 3-wire connector.

4. 4

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

5. 5

   With the black multimeter test lead probe the terminal that connects to the BLK/WHT wire of the engine wiring harness TPS connector.
   
   NOTE: Gently probe the female terminal with your multimeter test lead to avoid damaging it.

6. 6

   The multimeter should report 10 to 12 Volts DC.

Let's take a look at what your test results mean:

CASE 1: Your multimeter reported 10 to 12 Volts DC. This result confirms that the WHT/BLK wire is delivering Ground from the PCM to the throttle position sensor.

You can conclude that the TPS is toast and needs to be replaced, as long as you've confirmed all of the following:

1. TEST 1 —The TPS signal voltage is missing or stuck, regardless of throttle plate position.
2. TEST 2 —The brown wire is delivering 4.5 to 5 Volts DC.
3. In this final test, the WHT/BLK wire is delivering Ground from the PCM.

NOTE: The TPS sensor assembly must be adjusted to specification after replacement. You can find the step-by-step adjustment procedure here: How To Test And Adjust The Idle Switch (1993-1995 3.0L V6 Nissan Quest).

CASE 2: Your multimeter did not report the indicated voltage. Double-check that the terminal you're probing actually connects to the WHT/BLK wire, then repeat the test.

If your multimeter still doesn't report 10 to 12 Volts DC, this confirms the TPS isn't getting the Ground it needs to create a signal the PCM can use. Although it's beyond the scope of this tutorial, your next step is to find out why this PCM-supplied Ground is missing and restore it to the circuit.

The most likely cause is an open-circuit in the WHT/BLK wire between the TPS connector and the PCM. Once the issue is solved, the TPS will produce a valid signal, Code 43 will clear, and any engine performance issues should go away.

More 3.0L V6 Nissan Quest Diagnostic Tutorials

You can find a complete list of tutorials for your 3.0L V6 Nissan Quest and Mercury Villager here:

• 3.0L V6 Nissan Quest Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The Fuel Pump (1993-1998 3.0L V6 Nissan Quest).
• How To Troubleshoot A Cylinder Misfire (1993-1998 3.0L V6 Nissan Quest).
• How To Test The Fuel Injectors (1993-1995 3.0L V6 Nissan Quest).
• How To Test For A Blown Head Gasket (1993-1998 3.0L V6 Nissan Quest).