How To Test The 1996-2003 3.8L Ford Windstar TPS

The 1996-2003 3.8L Ford Windstar throttle position sensor is a three wire sensor that can be easily and accurately tested with a multimeter.

With the help of this tutorial, you'll be able diagnose a malfunctioning throttle position sensor and or troubleshoot diagnostic trouble codes (DTCs) P0121, P0122, P0123 on your Ford 3.8L V6 equipped Windstar mini-van.

The throttle position sensor diagnostic test is divided into three parts. All of them are explained in a step-by-step way.

I've written several other Ford 3.8L specific 'how to' tutorials that you can find at: Ford 3.0L And 3.8L Index Of Articles.

Symptoms Of A Bad TPS

You'll have the check engine light on, for sure, on your instrument cluster and one of several of the following symptoms:

1. TPS diagnostic trouble codes (DTCs) stored in the vehicle's computer's memory.
2. Really bad gas mileage. You know that it's not the price of gasoline that has you thinking that your mini-van is costing you more at the pump.
3. Transmission does not shift out of second gear. Now, this doesn't happen very often, but it happens.
4. No power and/or hesitation as you accelerate the vehicle. It feels like all of a sudden someone cut the power out momentarily as you step on the gas to get the vehicle moving.

How The Throttle Position Sensor Works

The throttle position sensor's job is to measure the angle of the throttle. So here, in a nutshell, is how the throttle position sensor works when you crank and start your 3.8L Ford mini-van:

1. The fuel injection computer supplies 5 Volts and Ground to the throttle position sensor.
2. Now, since the throttle is closed, the TPS (with power and Ground supplied) sends the PCM (Powertrain Control Module=Fuel Injection Computer) a DC voltage signal of about 0.9 to 1 Volt. This value is what the PCM associates with a closed throttle.
3. Once you throw the mini-van 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 PCM.
4. With this increasing voltage signal, the PCM knows it's time to inject more fuel, advance ignition timing, and a host of other things it has to do to keep your 3.8L Ford Windstar 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 PCM as it returns to its base voltage signal, till the whole cycle begins again.

Pretty easy stuff? The cool thing is that the tests to check out the TP sensor's performance are as easy too. Now, since you'll be working in the engine compartment take all necessary safety precautions and use common sense. OK, enough of my yakking, let's get this show on the road and get testing.

Where To Buy The TPS And Save

The best place to buy the TPS is online. The following links will help you to comparison shop for the throttle position sensor:

Not sure if the above TP sensor fits your particular 3.8L Ford Windstar? 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.

TPS TEST 1: Testing The TPS Signal

The first order of business, to find out if the throttle position sensor (TPS) is bad or not, is to see if it's producing a throttle position signal.

You'll need someone to help you test the throttle position sensor. OK, let's start:

PART 1

1. 1

   Start and warm up the engine on your 3.8L Ford Windstar mini-van. It's important that the throttle position sensor be at normal engine operating temperature.

2. 2

   Select Volts DC Mode on your multimeter and with the red multimeter test lead, probe the gray with white stripe (GRY/WHT) wire of the throttle position sensor. This is the wire that connects to the TPS terminal labeled with the number 2 in the illustration above.
   
   The throttle position sensor, on your 3.8L Ford mini-van's engine, has to remain connected to its electrical connector while doing this test.

3. 3

   Ground the black multimeter test lead on the battery negative (-) terminal and then have your helper turn the Key On but don't start the engine.

4. 4

   You should see your multimeter register 0.5 to 0.9 Volts DC. If it doesn't, don't worry about it just yet, continue with the other steps.

PART 2

1. 5

   Now, slowly rotate the throttle manually while you observe your multimeter.
   
   For this test result to be accurate, you need to rotate the throttle by hand and not from inside the mini-van.

2. 6

   As the throttle opens, the voltage reading should increase smoothly and without any gaps or skips. Once the throttle is wide open, your multimeter should read about 4.5 to 4.9 Volts DC.

3. 7

   Now, slowly return the throttle to its closed position. As this is happening, the voltage readings, on your multimeter, should decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 4.

PART 3

1. 8

   OK, now you'll need someone to help you 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.
   
   The purpose of the tapping is to see if this will cause gaps or skips in the voltage readings. If the TPS is good, no amount of tapping will cause the multimeter voltage readings to skip or go dead.

2. 9

   Repeat step 8 several times to make sure of your multimeter test results.

Let's interpret your test result:

CASE 1: The multimeter registered a smooth increase or decrease in voltage with no gaps. This test result confirms the throttle position sensor, on your 3.8L Ford mini-van, is good and you don't need to do TPS TEST 2 or 3.

Now, if the throttle position sensor code won't go away, take a look at the info found at: TPS Code Will Not Go Away for a few more suggestions as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: The multimeter DID NOT register a smooth increase or decrease in voltage and you saw the voltage reading skip or go dead when tapping the TPS. This test result means that the throttle position sensor (TPS) is bad. Replace the throttle position sensor.

CASE 3: The multimeter DID NOT register any voltage. This is not good, but doesn't condemn the TPS as bad yet.

The TPS may be missing either power or Ground and you can test these also, go to: TPS TEST 2: Testing The 5 Volt Reference Signal.