How To Test The TPS (1991-1995 3.3L Grand Caravan And Grand Voyager)

The throttle position sensor (TPS), on the 1991-1995 3.3L V6 Dodge Grand Caravan (Plymouth Grand Voyager), can be easily tested with a multimeter.

In this tutorial I'll show you how the test is done. With your test results you'll be able to find out if the throttle position sensor is bad or not.

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1991-1995 3.3L Grand Caravan y Grand Voyager) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles (since they use the exact same throttle position sensor):

• 3.3L V6 Dodge Grand Caravan: 1991, 1992, 1993, 1994, 1995.
• 3.3L V6 Plymouth Grand Voyager: 1991, 1992, 1993, 1994, 1995.

Symptoms Of A Bad TPS

As you're probably already aware, the throttle position sensor has the job of measuring how much the throttle plate opens or closes as you step on or off the accelerator pedal.

This throttle angle measurement is then sent to your mini-van's fuel injection computer.

Since the TPS signal is monitored the entire time the engine is running, when it fails the check engine light will illuminate on your mini-van's instrument cluster.

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

1. TPS diagnostic trouble codes (DTC's).
   • Code 24: Throttle Position Sensor Voltage Low.
   • Code 24: Throttle Position Sensor Voltage High.
2. Bad gas mileage.
3. No power and/or hesitation as you accelerate the vehicle.
4. The engine loses power all of a sudden as you step on the accelerator pedal when driving the vehicle.
5. Engine does not start.

How The Throttle Position Sensor Works

The throttle position sensor is a simple 3-wire component. And in a nutshell:

1. The fuel injection computer supplies 5 Volts and Ground to the throttle position sensor.
   • 5 Volts is provided by the violet with white stripe (VIO/WHT) wire labeled with the number 1.
   • Ground is provided by the black with light blue stripe (BLK/LT BLU) wire labeled with the number 3.
2. Now, since the throttle is closed, the TPS sends the fuel injection computer a DC voltage signal of about 0.3 to 0.9 Volt. This value is what the fuel injection computer associates with a closed throttle.
   • The TP signal is sent to the fuel injection computer by the dark blue (DK BLU) wire labeled with the number 2.
3. Once you throw your 3.3L V6 Dodge Grand Caravan (Plymouth Grand Voyager) in drive and accelerate it, the throttle opens and the throttle position sensor immediately sends this change of the throttle angle as an INCREASING voltage signal to the fuel injection computer.
4. With this increasing voltage signal, the fuel injection computer knows its time to inject more fuel, advance ignition timing, and a host of other things it has to do to keep your mini-van running optimally.
5. As you let go off the accelerator pedal to slow down, the throttle plate closes and of course the TP sensor sends the info to the fuel injection computer as it returns to its base voltage signal, till the whole cycle begins again.

Pretty easy stuff? It's just as easy to test the TP sensor's performance too.

Where To Buy The TPS And Save

If you find that the throttle position sensor is bad, check out following links and comparison shop. I think they'll help you save a few bucks on its purchase.

Not sure if the above throttle position sensor (TPS) fits your particular 3.3L V6 Dodge Grand Caravan or 3.3L V6 Plymouth Grand Voyager? 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 Signal With A Multimeter

Generally, when the throttle position sensor fails, it will stay stuck producing a single voltage value as the throttle plate is opened and closed.

So, for our first test, we'll verify what the TPS signal voltage is doing while opening and closing the throttle plate.

We'll accomplish this by connecting a multimeter to the TPS signal wire and then we'll open/close the throttle plate as we monitor the TPS signal voltage (on the multimeter).

If the signal voltage does not increase/decrease as we open/close the throttle plate, then we can conclude that the TPS is malfunctioning.

On the 1991-1993 3.3L V6 Dodge Grand Caravan and Plymouth Grand Voyager, the wire that we're gonna' connect the multimeter to, is the orange with dark blue stripe (ORG/DK BLU) wire of the connector.

On the 1994-1995 3.3L V6 Dodge Grand Caravan and Plymouth Grand Voyager, the wire that we're gonna' connect the multimeter to, is the dark blue (DK BLU) wire of the connector.

On all vehicles (1991-1995) the TPS signal wire is the middle wire of the connector and I've labeled this wire with the number 2 (in the photo above).

NOTE: The throttle position sensor must remain connected to its electrical connector to perform this test. To access the signal voltage inside the wire, you'll need to back probe the connector or use a wire piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe.

OK, let's start:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

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

3. 3

   Connect the red test lead to the TPS signal wire. This wire is the middle wire of the connector and is labeled with the number 2 in the photo above.
   
   NOTE: The TP sensor connector needs to be connected to the TPS, so you'll need to either back-probe the connector or use a wire piercing probe to get to the signal inside the wire.

4. 4

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

5. 5

   At this point (with the throttle plate closed) your multimeter should read a voltage between 0.3 to 1.0 Volts DC.

6. 6

   Manually rotate the throttle plate.
   
   You'll get the best results by opening and closing the throttle plate directly on the throttle body instead of stepping on the accelerator pedal.

7. 7

   The multimeter should show an increasing voltage as you (or your helper) open up the throttle plate.
   
   With the throttle plate completely open, your multimeter should read: 3.2 to 4.9 Volts DC.

8. 8

   The multimeter should show a decreasing voltage as you begin to close the throttle.

9. 9

   Using a screwdriver's handle, gently tap the TP sensor as you open and close the throttle and observer the multimeter.
   
   The purpose (of tapping the TP sensor with the screwdriver's handle) is to see if the TP sensor shows gaps in the voltage signal. Why? Because a good TP sensor will show a continuous increasing or decreasing voltage signal even while getting tapped by the screw-driver's handle.

Let's examine your test results:

CASE 1: The signal voltage increased/decreased as you opened/closed the throttle plate. This is the correct test result and confirms that the throttle position sensor is good (not defective).

If the check engine light still illuminates with a TPS trouble code, take a look at the suggestions in this section: The TPS Code Won't Go Away.

CASE 2: The signal voltage value DID NOT increase/decrease as you opened/closed the throttle plate. You can generally conclude that the TPS sensor is bad and that it needs to be replaced.

But to be sure that the TPS is bad, it's important to verify that it's getting 5 Volts and Ground. For the first of these two tests, go to: TEST 2: Making Sure The TPS Is Getting 5 Volts.

CASE 3: The TPS voltage signal had gaps in its reading as you tapped the TPS with the screwdriver. This test result tells you that the TPS is bad and needs to be replaced.