How To Test A BAD Fuel Injector (2.6L Isuzu Pick Up)

The throttle position sensor (TPS) is called the Wide Open Throttle Switch or the Throttle Valve Switch by the Isuzu service literature... and in this tutorial, I'll show you how to test it.

Here are the contents of this article at a quick glance:

  1. Symptoms of Bad Throttle Valve Switch.
  2. TEST 1: Making Sure The WOT Switch Is Getting Power.
  3. TEST 2: Testing The Continuity Of The Idle Circuit.
  4. TEST 3: Testing The Continuity Of The WOT Circuit.
  5. Adjusting the Throttle Valve Switch.
  6. Where To Buy The Throttle Valve Switch And Save.
  7. More 2.6L Isuzu Tutorials

Symptoms of Bad Throttle Valve Switch

Since the Isuzu's covered by this tutorial are OBD I equipped, a failed throttle position sensor (throttle valve switch) will set a diagnostic trouble code (TDC) and light up the check engine light on your 2.6L Isuzu Rodeo (Pick Up, Amigo).

Depending on the type of failure of the throttle valve switch, you'll see:

  1. Trouble codes:
    1. Trouble Code 21: Throttle Valve Switch (Idle and WOT).
    2. Trouble Code 43: Throttle Valve Switch (Idle Position).
    3. Trouble Code 65: Throttle Valve Switch (Full Throttle).
  2. High idle.
  3. Rough idle.

Testing the throttle valve switch and/or adjusting it is a pretty easy affair. I'll explain how in the next sub-headings and pages.

TEST 1: Making Sure The WOT Switch Is Getting Power

How To Test A BAD Fuel Injector (2.6L Isuzu Pick Up)

The first order of business, is to check the basics. So, we'll check/confirm that the throttle valve switch is getting power.

This power is in the form of battery voltage (10 to 12 volts DC) and is provided by the middle wire of the throttle valve switch.

The illustration above is a representation of the front view of the throttle valve switch's connector. To be a bit more specific, the front view is the view that shows the metal terminals of the connector.

We'll use a multimeter for the test:

Alright, here are the steps:

  1. 1

    Disconnect the throttle valve switch from its engine wiring harness connector and set your multimeter to Volts DC mode.

  2. 2

    With the red multimeter lead, probe the middle wire's terminal.

    NOTE: Probe the terminal gently and without a lot of pressure/force or you'll damage the terminal.

  3. 3

    Ground the multimeter's black test lead on the battery's negative post or a clean/rust free spot on the engine.

  4. 4

    The multimeter should register 10-12 Volts DC with the key in the ON position.

Let's take a look at what you test results mean:


CASE 1: The throttle valve switch is being fed power. So far so good. This test result confirms that the throttle valve switch is getting power.

Your next test is to check the continuity of the idle circuit and the wide open throttle circuit (inside the throttle valve switch). For the first of these two tests, go to: TEST 2: Testing The Continuity Of The Idle Circuit.

CASE 2: The throttle valve switch IS NOT being fed power. Double check your multimeter connections and retest. If still no voltage... then you've found the problem causing the TV switch trouble code.

Finding and repairing the cause of this missing voltage will get the throttle valve switch back to work and solve the trouble code.