Testing the throttle position sensor is a piece of cake on the 1998, 1999, and 2000 2.4L Dodge Caravan and Plymouth Voyager.
What makes this test so easy is the fact the the throttle position sensor is very accessible (see photo above).
In this tutorial I'm going to show you how to test the TPS with 3 simple multimeter tests that you'll be able to accomplish in a matter of minutes.
And in case you're wondering, you don't need a scan tool to diagnose the throttle position sensor is good or bad. I'm also going to show you where you can buy it and save a few bucks on its purchase.
Contents of this tutorial:
You can find this tutorial in Spanish here: Probando El Sensor TPS (1998-2000 2.4L Dodge, Plymouth Mini-Van) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles (since they use the exact same throttle position sensor):
- 2.4L Dodge Caravan: 1998, 1999, 2000.
- 2.4L Plymouth Voyager: 1998, 1999, 2000.
Symptoms Of A Bad TPS
The throttle position sensor's job is to measure the angle of the throttle plate, in the throttle body, as you step on or step off the accelerator pedal.
This throttle angle information is then sent to the fuel injection computer.
The fuel injection computer then uses this information to inject more or less fuel, advance ignition timing and a few other things to keep the engine running optimally.
Since the throttle position sensor is monitored constantly, when the engine is running, when it fails it's going to light up the check engine light with one or more of the following trouble codes:
- P0121: TPS Voltage Does Not Agree with MAP.
- P0122: Throttle Position Sensor Voltage Low.
- P0123: Throttle Position Sensor Voltage High.
Since the throttle position sensor is such a critical component of the engine management system, you're also going to see one or more of the following symptoms would fails:
- Bad gas mileage.
- No power and/or hesitation as you accelerate the vehicle.
- The engine loses power all of a sudden as you step on the accelerator pedal when driving the vehicle.
- Engine does not start.
The cool thing is that testing it is very easy. All right, with this information under our belts, let's move on to the next subheading.
How The Throttle Position Sensor Works
To successfully diagnose and test the throttle position sensor as good or bad, it's important to know how it functions.
I mentioned earlier, its job is to report the throttle plate angle to the fuel injection computer. To be a bit more specific, when you turn the key on and start the engine, this is what happens:
- 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.
- 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 orange with dark blue stripe (ORG/DK BLU) wire labeled with the number 2.
- Once you throw your 2.4L Dodge Caravan (Plymouth 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.
- 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.
- 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.
Piece of cake, right? It's just as easy to find out if the throttle position sensor is OK or if it's bad.
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 2.4L Dodge Caravan or 2.4L Plymouth 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
The first test we're going to do is to find out if the TPS voltage signal increases/decreases as we open/close the the throttle plate.
If the throttle position sensor is bad, it'll usually stay stuck producing a single voltage value as the throttle plate opens/closes.
If the sensor is OK, then its voltage signal will increase/decrease as the throttle plate opens/closes.
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:
Place your multimeter in Volts DC mode.
Turn the key ON but don't crank or start the engine.
Connect the red test lead to the TPS signal wire.
This wire is the middle wire of the connector and it connects to the terminal 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.
Ground the black multimeter test lead directly on the battery negative (-) post.
At this point (with the throttle plate closed) your multimeter should read a voltage between 0.3 to 1.0 Volts DC.
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.
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.
The multimeter should show a decreasing voltage as you begin to close the throttle.
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.