The throttle position sensor (TPS) on the 1987-1991 3.0L Toyota Camry combines two sensors into one unit: an idle switch and the actual throttle position sensor.
In this guide, I'll focus on testing the throttle position sensor portion of the assembly. With just a multimeter, we'll determine if the TPS is functioning properly or if it needs replacement, and the process is quick and straightforward.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 3.0L Toyota Camry: 1992, 1993, 1994, 1995, 1996.
Idle Switch Tests: The following tutorial will show you how to test the idle switch part of the TPS sensor. It also explains how to adjust the TPS:
Symptoms Of A Bad Throttle Position Sensor
The throttle position sensor plays a critical role in your Camry's engine management system by sending a voltage signal to the fuel injection computer.
This signal tells the computer the precise position of the throttle plate, allowing it to make necessary adjustments to fuel injection and ignition timing.
A failing TPS can cause the following issues:
- OBD I Trouble Code 41: Indicates a TPS signal problem.
- Hesitation: The engine stumbles during acceleration.
- Loss of Power: Reduced engine performance is noticeable.
- Poor Fuel Economy: Gas mileage takes a hit due to incorrect fuel delivery.
,
it's time to test the TPS.How The TPS Works
The TPS on your 3.0L V6 Toyota Camry has two primary functions:
- Throttle Position Detection: It generates a voltage signal based on how much the throttle plate is opened. The computer uses this signal to adjust:
- Fuel injection timing.
- Ignition timing.
- Other parameters for optimal engine performance.
- Idle Position Switch: Built into the TPS, the idle switch activates when the throttle plate is closed. It tells the computer the engine is idling, which allows it to:
- Stabilize the idle speed.
- Manage fuel delivery during deceleration.
- Maintain a consistent idle.
How It Works in Practice:
- At Idle: The idle switch signals the computer, and TPS voltage is at its lowest (about 0.5 volts).
- During Acceleration: Voltage increases smoothly as the throttle plate opens.
- Wide-Open Throttle (WOT): Voltage peaks around 4.5 Volts, prompting maximum fuel delivery and timing adjustments.
- Deceleration: The idle switch re-engages, cutting fuel flow momentarily to improve efficiency.
Circuit Descriptions Of The TPS
| Terminal | Wire | Description |
|---|---|---|
| 1 | Brown (BRN) | Sensor Ground |
| 2 | 1992-1994: Blue (BLU) | Idle Switch Signal |
| 1995-1996: Blue with white stripe (BLU/WHT) | ||
| 3 | 1992-1993: Black (BLK) | TPS Signal |
| 1994-1996: Black with yellow stripe (BLK/YEL) | ||
| 4 | 1992-1993: Red (RED) | 5 Volts |
| 1994-1996: Blue with red stripe (BLU/RED) |
Where To Buy The TPS And Save
The following links will help you to comparison shop for a new 3.0L Camry TPS. I think they'll save you a few bucks:
Not sure if the above TPS fits your particular 3.0L Toyota Camry? Don't worry, once you get to the site they'll make sure it fits by asking you the specifics of your particular Toyota vehicle. If it doesn't fit, they'll find you the right one.
TEST 1: Testing The TPS Voltage Signal
The TPS generates an analog voltage signal that changes as the throttle plate opens and closes. We can easily test it with a multimeter to see if it's working correctly.
At wide-open throttle (WOT), the voltage typically reaches about 4.5 Volts DC. When the throttle plate is closed, the voltage returns to its baseline value.
To diagnose the TPS, we'll check if the throttle position voltage rises and falls smoothly as the throttle plate is manually opened and closed.
A faulty TPS will produce a fixed voltage reading on the multimeter that doesn't change, no matter how the throttle plate moves.
IMPORTANT: Leave the TPS connected to its harness connector while testing. You'll need to back-probe the connector or use a wire-piercing probe to measure the voltage.
Here are the steps:
- 1
Turn the key to the ON position but don't start the engine.
- 2
Place your multimeter in Volts DC mode.
- 3
Ground the black multimeter test lead on the battery negative (-) terminal.
- 4
Connect the red multimeter test lead to the black (BLK) or black with yellow stripe (BLK/YEL) wire of the TPS 4-wire connector.
1992-1993: Terminal number 3 corresponds to the black (BLK) wire of the connector.
1994-1996: Terminal number 3 corresponds to the black with yellow stripe (BLK) wire of the connector. - 5
Your multimeter should report a voltage between 0.2 to 0.9 Volts DC with the throttle plate closed.
If your multimeter doesn't, don't worry about it just yet, continue to the next step. - 6
Slowly open the throttle plate (by hand and from the engine compartment).
The voltage numbers should increase as the throttle plate opens.
This increase in voltage should be smooth and without any gaps or skips. Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC. - 7
Slowly close the throttle.
As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 5. - 8
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.
If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers. - 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 voltage increased and decreased as you opened and closed the throttle plate. This confirms the TPS is working properly. No further testing is required.
CASE 2: The voltage DID NOT increase/decrease) as you opened and closed the throttle plate. This test result generally confirms the throttle position sensor is bad.
To make sure the TPS is bad, we need to make sure it's getting power and Ground. For the first of these two tests, go to: TEST 2: Making Sure The TPS Is Getting 5 Volts.
CASE 3: The multimeter DID NOT register any voltage. This test result generally confirms the throttle position sensor is bad.
To make sure the TPS is bad, we need to make sure it's getting power and Ground. For the first of these two tests, go to: TEST 2: Making Sure The TPS Is Getting 5 Volts.