How To Test The TPS (1992-1996 5.2L, 5.9L Dodge Ram Pickup/Van)

The throttle position sensor (TPS) can be very accurately tested with a multimeter to see if it's bad or not without removing it.

In this tutorial, I'll show you just how in a step-by-step manner. You'll also be able to diagnose the following throttle position sensor (TPS) diagnostic trouble codes:

NOTE: For the 3.9L V6 equipped Dodge pickup and van, see this tutorial: How To Test The TPS (1992-1996 3.9L Dodge Ram Pickup/Van).

• Trouble Code 24: TPS Voltage Low.
• Trouble Code 24: TPS Voltage High.
• P0121: TPS Voltage Does Not Agree with MAP (OBD II).
• P0122: Throttle Position Sensor Voltage Low (OBD II).
• P0123: Throttle Position Sensor Voltage High (OBD II).

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

• Ram 1500 Pickup 5.2L, 5.9L: 1994, 1995, 1996.
• Ram 2500 Pickup 5.2L, 5.9L: 1994, 1995, 1996.
• Ram 3500 Pickup 5.9L: 1994, 1995, 1996.
• Ram B150 Van 5.2L: 1992, 1993, 1994.
• Ram B250 Van 5.2L, 5.9L: 1992, 1993, 1994.
• Ram B350 Van 5.9L: 1992, 1993, 1994.
• Ram B1500 Van 5.2L: 1995, 1996.
• Ram B2500 Van 5.2L, 5.9L: 1995, 1996.
• Ram B3500 Van 5.2L, 5.9L: 1995, 1996.
• Ram D150 Pickup 5.2L, 5.9L: 1992, 1993.
• Ram D250 Pickup 5.2L, 5.9L: 1992, 1993.
• Ram D350 Pickup 5.9L: 1992, 1993.
• Ram W150 Pickup 5.2L, 5.9L: 1992, 1993.
• Ram W250 Pickup 5.2L, 5.9L: 1992, 1993.
• Ram W350 Pickup 5.9L: 1992, 1993.

Basics Of The Throttle Position Sensor (TPS)

The throttle position sensor's job is to measure the angle of the throttle plate. As you're already aware, it's the throttle plate that allows a varying amount of air into the engine (as you step on or off the accelerator pedal).

As the throttle plate angle increases (like when you're stepping on the accelerator pedal), the TPS creates an increasing voltage signal. This voltage signal is sent to your pickup's fuel injection computer (known in tech speak as the PCM -Powertrain Control Module) on the middle wire of the TP sensor connector.

As the throttle plate angle decreases (like when you're letting your foot off of the accelerator pedal), the TPS decreases the throttle angle voltage signal.

So, in a nutshell, the key to troubleshooting the TP sensor is to make sure that it is creating an increasing/decreasing throttle angle voltage signal with a multimeter (and that's exactly what we'll do in this tutorial).

In the table below, you'll find a short description of what each wire does:

1992-1996 Dodge Ram TPS Circuits
Pin	Wire Color	Description
1	BLK/LT BLU	Sensor Ground
2	ORG/DK BLU	Throttle Position Signal
3	VIO/WHT	5 Volts

Where To Buy The TPS And Save

You can buy the throttle position sensor for your Dodge Ram pickup in just about any auto parts store but you'll spend a whole lot more because they mark it up quite a bit.

My suggestion is to buy it online or at least comparison shop to get an idea of how much it costs and how much you can save.

The following links:

TEST 1: Checking The Throttle Position Sensor (TPS) Signal

The most common throttle position sensor (TPS) failure is a sensor that just stops creating a varying throttle angle voltage signal.

In other words, it stops measuring/reporting the throttle angle of the throttle plate. You and I can very easily check this with a multimeter and that's what we'll do in this test section.

IMPORTANT: The throttle position sensor must remain connected to its harness connector to accomplish this test.

Here are the test steps:

1. 1

   Place your multimeter in Volts DC mode and connect the red test lead to the ORG/DK BLU of the TP sensor harness connector (see image 1 of 2).
   
   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 (to see what a wire piercing probe looks like: Wire Piercing Probe Tool).

2. 2

   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 volt DC.

3. 3

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

4. 4

   The multimeter should show an increasing voltage as you (or your helper) open up the throttle.
   
   With the throttle plate completely open, your multimeter should read: 3.2 to 4.9 Volts DC.
   
   You'll get the best results by opening and closing the throttle directly on the throttle body instead of stepping on the accelerator pedal.

5. 5

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

6. 6

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

CASE 1: The voltage increased and decreased smoothly and without gaps. This tells that the throttle position sensor on your Dodge Ram IS NOT defective.

Since the throttle position sensor is creating an increasing/decreasing voltage signal on the ORG/DK BLU wire, this test result also says that:

1. The TPS is getting power on the VIO/WHT wire of its harness connector.
2. The TPS is getting Ground on the BLK/LT BLU wire of its harness connector.

CASE 2: The voltage DID NOT increase or decrease. This test result usually means that the throttle position sensor on your Dodge Ram is bad and needs to be replaced.

Before replacing the TPS, I suggest that you verify that it's getting power and Ground. So, to continue with the TPS diagnostic, go to: TEST 2: Making Sure The TPS Is Getting Power.

CASE 3: The TP sensor signal's voltage showed gaps in its voltage output as you tapped the sensor with the screwdriver. If the gaps in the multimeter's voltage readings only showed up when you were tapping on the TPS (with the screwdriver's handle) then this test result tells you that the TPS is bad and needs to be replaced.