The throttle position sensor (TPS) on the 1987-1991 2.0L Toyota Camry with an automatic transmission combines two sensors into a single assembly.
One part functions as an idle switch, while the other is the actual throttle position sensor.
In this tutorial, I'll show you how to test the throttle position sensor portion of the assembly.
We'll use a multimeter, to quickly and easily determine if the TPS is working properly or if it needs to be replaced.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles with automatic transaxle:
- 2.0L Toyota Camry: 1997, 1988, 1989, 1990, 1991
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:
TPS Test w/ Manual Transaxle:
Symptoms Of A Bad Throttle Position Sensor
The throttle position sensor (TPS) sends a voltage signal to the fuel injection computer, indicating the precise position of the throttle plate. This data is crucial for several functions, including adjusting fuel injection and advancing ignition timing.
Because the TPS is such a vital component of your 2.0L Camry's engine management system, a malfunctioning sensor can cause one or more of the following issues:
- OBD I Trouble Code: You may see diagnostic trouble code 41, which indicates a problem with the TPS signal.
- Hesitation: The engine may stumble or hesitate during acceleration.
- Loss of Power: A faulty TPS can lead to noticeable power reduction.
- Poor Fuel Economy: You might experience worse gas mileage due to incorrect fuel delivery.
How The TPS Works
As mentioned at the beginning, the throttle position sensor (TPS) comes with an integrated idle switch and it's a key component of your 1987-1991 2.0L Toyota Camry's engine management system.
The Two Main Functions of the TPS- Throttle Position Detection: The TPS generates a voltage signal that changes based on how far the throttle plate is opened. This signal tells the computer whether the throttle is closed (idle), partially open (cruising), or fully open (wide-open throttle). The computer uses this data to adjust:
- Fuel injection timing.
- Ignition timing.
- Other engine parameters to match driving conditions.
- Idle Position Switch: The idle switch, built into the TPS, activates when the throttle plate is completely closed. This signal informs the computer that the engine is idling, which allows it to:
- Adjust the idle speed.
- Turn off fuel delivery during deceleration (if necessary).
- Ensure a stable idle by managing air and fuel flow.
In a nutshell, this is how the TPS works on your 2.0L Toyota Camry:
- At Idle: When your foot is off the gas pedal, the throttle plate is closed, and the idle switch sends a signal to the computer. The TPS voltage output is at its lowest value (typically around 0.5 volts), confirming the throttle's position.
- During Acceleration: As you press the gas pedal, the throttle plate opens, and the TPS voltage increases. This tells the computer how much fuel is needed to match the increased airflow.
- Wide-Open Throttle (WOT): When the throttle plate is fully open, the TPS voltage peaks (around 4.5 volts). The computer maximizes fuel delivery and adjusts timing to provide the most power.
- Deceleration: If the throttle is suddenly released, the idle switch reactivates, signaling the computer to cut fuel flow momentarily, improving fuel efficiency and reducing emissions.
Circuit Descriptions Of The TPS
| Terminal | Wire | Description |
|---|---|---|
| 1 | Blue with red stripe (BLU/RED) | 5 Volts |
| 2 | Black with red stripe (BLK/RED) | TPS Signal |
| 3 | Blue (BLU) | Idle Switch Signal |
| 4 | Brown (BRN) | Sensor Ground |
Where To Buy The TPS And Save
The following links will help you to comparison shop for a new 2.0L Camry TPS. I think they'll save you a few bucks:
Not sure if the above TPS fits your particular 2.0L 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 produces an analog voltage signal that we can easily test using a multimeter. This voltage signal rises as the throttle plate opens.
At wide open throttle, the voltage peaks at around 4.5 Volts DC. When the throttle plate is released, the voltage drops back to its original value.
To begin diagnosing the TPS, we'll measure whether the throttle position voltage increases and decreases smoothly as we manually open and close the throttle plate.
If the TPS is faulty, the multimeter will display a static value that doesn't change as you move the throttle plate.
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. You can see an example of this tool (and where to buy it) here: Wire Piercing Probe.
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 with red stripe (BLK/RED) wire of the TPS 4-wire connector.
This BLK/RED should connect to TPS male spade terminal identified with the number 2 in the illustration above. - 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 is the correct and expected test result.
This result confirms that the TP sensor is OK and not defective.
CASE 2: The voltage DID NOT increase (and/or decrease) as you opened and closed the throttle plate. This test result confirms the throttle position sensor is behind the trouble code lighting up the check engine light on your 2.0L Toyota Camry.
The next step is to be sure that the TPS is getting both 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 usually means the TPS is bad.
To make sure the TP sensor is bad, we need to check that it's getting power and Ground. The next step is to check that the TP sensor is getting them power, go to: TEST 2: Making Sure The TPS Is Getting 5 Volts.
