This tutorial will help you to test the throttle position sensor on the 1998-2003 2.2L Isuzu Rodeo and Amigo.
The TPS is a simple 3-wire component that can be easily tested with a multimeter. You don't need a scan tool (although having one is great).
In this tutorial, I'll explain how to test it in a step-by-step manner. You'll be able to easily find out if the TPS is bad or not.
Contents of this tutorial:
NOTE: This tutorial applies to the following vehicles since they use the exact same throttle position sensor:
- 2.2L Isuzu Amigo: 1998, 1999, 2000, 2001, 2002, 2003.
- 2.2L Isuzu Rodeo: 1998, 1999, 2000, 2001, 2002, 2003.
Symptoms Of A Bad Throttle Position Sensor
The throttle position sensor has the job of measuring the amount the throttle plate opens as you step on or off the accelerator pedal.
To be a bit more specific, the throttle position sensor produces a voltage signal that increases as you step on the accelerator pedal and the throttle plate opens.
When you step off the accelerator pedal and the throttle plate starts to close, the TPS voltage signal decreases back to its original base voltage.
All of these changes of the throttle plate angle, are constantly reported to your Isuzu Rodeo's fuel injection computer.
Since the throttle position sensor (TPS) is such an important component of the fuel injection system of your 1998-2003 2.2L Isuzu Rodeo, when it fails you're gonna' definitely feel the engine resent it.
You're going to see the following TPS diagnostic trouble code lighting up the check engine light:
- P0122 TPS Voltage Too Low.
- P0123 TPS Voltage Too High.
You're also going to see one or more of the following symptoms:
- Won't pass the state mandated emissions test.
- Bad gas mileage.
- Lack of power, rough idle, or hesitation.
- Engine cranks a long time before starting.
Throttle Position Sensor (TPS) Circuit Descriptions
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| Terminal | Wire | Description |
|---|---|---|
| 1 | RED | 5 Volts |
| 2 | Green (GRN) | Sensor Ground |
| 3 | Blue (BLU) | TPS Signal |
Where To Buy The TPS And Save
The 1998-2003 2.2L Isuzu Rodeo's TPS is a pretty inexpensive component. The following links will help you to comparison shop and hopefully save you a few bucks on its purchase:
NOTE: The above throttle position sensor (TPS) fits the following vehicles: 1998, 1999, 2000, 2001, 2002, 2003 2.2L Isuzu Rodeo And Amigo.
TEST 1: Testing The TPS Voltage Signal
The important thing to remember when testing the TPS, is that its voltage signal increases as the throttle plate opens and as it closes, the voltage decreases.
If the throttle position sensor is bad, it'll usually stay stay producing one voltage value as you open/close the throttle plate.
For our first test we're gonna' connect the multimeter to the TPS signal wire and see if TPS voltage signal increases/decreases as we open/close the throttle plate.
The wire that we're gonna' connect the multimeter to is the blue (BLU) wire of the connector.
In the photo above, I've labeled the BLU wire with a number 3.
IMPORTANT: The throttle position sensor (TPS) must remain connected to its electrical connector for this test to function properly. To be able to access the voltage inside the signal wire, you'll need to use either a back probe or a wire piercing probe. You can see an example of this tool here: Wire Piercing Probe.
Let's get started:
- 1
Place your multimeter in Volts DC mode.
- 2
Connect the red test lead to the BLU wire of the TP sensor harness connector.
- 3
Ground the black multimeter test lead directly on the battery negative (-) post.
- 4
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. - 5
The multimeter should show an increasing voltage as you (or your helper) open up 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. - 6
The multimeter should show a decreasing voltage as you begin to close the throttle.
- 7
Using a screwdriver's handle, gently tap the TP sensor as you open and close the throttle and observe 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 analyze your test results:
CASE 1: The TPS voltage signal increased/decreased as you opened/closed the throttle plate. This is the correct test result and it confirms that the throttle position sensor is OK (not bad).
With this test result you can also conclude that the TPS sensor is getting both power (5 Volts) and Ground from the fuel injection computer.
CASE 2: The TPS voltage signal DID NOT increase/decrease as you opened and closed the throttle. This test result usually indicates that the TPS sensor is defective.
To make sure the TPS sensor is bad the next step is to check that the red wire is feeding the TPS with 5 Volts. For this test go to: TEST 2: Making Sure The TPS Has 5 Volts.
CASE 3: The multimeter DID NOT register any voltage. This test result usually indicates that the TPS sensor is defective.
To make sure the TPS sensor is bad the next step is to check that the red wire is feeding the TPS with 5 Volts. For this test go to: TEST 2: Making Sure The TPS Has 5 Volts.
