How To Test APP Sensor 1 And APP Sensor 2 (2007, 2008, 2009 3.5L Chevrolet Malibu and 3.5L Pontiac G6)

In this tutorial I'm gonna' show you how to test APP sensor 1 and APP sensor 2 of the accelerator pedal assembly.

Each APP sensor can be tested with 3 easy multimeter resistance tests and in this tutorial you'll find them explained in a step-by-step manner.

With your test results you'll be able to correctly diagnose the APP sensor assembly as defective or not.

NOTE: This tutorial applies to the following vehicles:

  1. 2005, 2006, 2007, 2008, 2009 3.5L V6 Chevrolet Malibu.
  2. 2005, 2006, 2007, 2008, 2009, 2010 3.5L V6 Pontiac G6.

Puedes encontrar este tutorial en Español aquí: Cómo Probar El Sensor APP (2007-2009 3.5L Chevrolet Malibu y Pontiac G6) (en: autotecnico-online.com).

NOTE: The following electronic throttle body test tutorial and TAC system wiring diagrams, with the APP sensor circuits, may come in handy:

  1. Accelerator Pedal Position Sensor Basics (2007-2009 3.5L Chevy Malibu And Pontiac G6).
  2. Electronic Throttle Body Tests (2007-2009 3.5L Chevrolet Malibu And Pontiac G6).
  3. Throttle Body (TAC) Circuit Wiring Diagram (2007-2009 3.5L Malibu).
  4. Throttle Body (TAC) Circuit Wiring Diagram (2004-2006 3.5L Malibu).

Symptoms Of A Bad APP Sensor

As you're already aware, the accelerator pedal position sensor assembly is made up of two APP sensors: accelerator pedal position (APP) sensor 1 and accelerator pedal position (APP) sensor 2.

When one or both fail, you're gonna' see one or more of the following symptoms:

  1. The check light engine light will be lit up by one of the following trouble codes:
    1. P2120: Accelerator Pedal Position (APP) Sensor 1 Circuit.
    2. P2122: Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage.
    3. P2123: Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage.
    4. P2125: Accelerator Pedal Position (APP) Sensor 2 Circuit.
    5. P2127: Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage.
    6. P2128: Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage.
    7. P2138: Accelerator Pedal Position (APP) Sensor 1 - 2 Correlation.
  2. Your Chevy Malibu (Pontiac G6) will run in Reduced Engine Power mode.
  3. The engine starts and runs but when you try to accelerate your Chevy Malibu (Pontiac G6), it accelerates very slowly.
  4. The engine starts and runs but the engine does not accelerate when you step on the accelerator pedal.
  5. The engine starts and runs but shuts down.

The cool thing is testing the accelerator pedal position sensors is not difficult at all. All you'll need is a multimeter and in this tutorial I'll explain how to test both APP sensor 1 and APP sensor 2.

NOTE: You can find out more about how the APP sensors work here: Accelerator Pedal Position Sensor Basics (2007-2009 3.5L Chevy Malibu And Pontiac G6).

APP Sensor Terminal Pin Out Chart

APP Sensor 1 And APP Sensor 2 Terminal Pin Out Chart. How To Test APP Sensor 1 And APP Sensor 2 (2007, 2008, 2009 3.5L Chevrolet Malibu and 3.5L Pontiac G6)

The engine wiring harness connector (of the APP sensor assembly) has 6 wires coming out of it and it has female type terminals.

The connector on the APP sensor assembly itself has 6 male spade terminals. The illustration above is of the connector on the APP sensor assembly itself.

Pin Wire Color Description
A PPL Sensor Ground
B LT BLU APP Sensor 2 Signal
C TAN 5 Volts
D BRN Sensor Ground
E DK BLU APP Sensor 1 Signal
F WHT/BLK 5 Volts

Both accelerator pedal positions sensors are the potentiometer type, which means we can easily test them with a multimeter. Let's get started with the first test.

WIRING DIAGRAM: You can the APP sensor circuit wiring diagram here: TAC Circuit Wiring Diagram (2007-2009 3.5L Chevy Malibu And Pontiac G6).

TEST 1: Testing The Resistance Between Terminals D And F (APP Sensor 1)

How To Test APP Sensor 1 And APP Sensor 2 (2007, 2008, 2009 3.5L Chevrolet Malibu and 3.5L Pontiac G6)

The first test we're gonna' start off with is making sure that the there's continuity between terminal D and F of APP sensor 1.

Terminal D is the terminal that gets Ground from your Chevy Malibu or Pontiac G6's fuel injection computer.

Terminal F is the terminal that gets 5 Volts from your Chevy Malibu or Pontiac G6's fuel injection computer.

NOTE 1: All multimeter connections are done on the male spade terminals of the APP sensor assembly itself.

NOTE 2: To make it easier to connect your multimeter test leads to the APP sensor assembly's terminals (and depress/release the accelerator pedal), I recommend that you use insulated alligator terminals on the ends of your multimeter test leads.

These are the test steps:

  1. 1

    Disconnect the APP sensor assembly from its electrical connector.

  2. 2

    Place your multimeter in Ohms mode.

  3. 3

    Connect the red multimeter test lead to terminal D.

  4. 4

    Connect the black multimeter test lead to terminal F.

  5. 5

    Your multimeter should read continuity.

    In my test result, I got 1.2 K Ohms for the resistance reading.

Let's examine your test results:

CASE 1: The multimeter registered continuity between terminals D and F. This is the correct test result.

The next step is to test the continuity of terminals E and F (of APP sensor 1) while we depress/release the accelerator pedal. For this test go to: TEST 2: Testing The Resistance Between Terminals E And F (APP Sensor 1).

CASE 2: The multimeter DID NOT register continuity between terminals D and F. This lets you know that APP sensor 1 is bad. With this test result you can conclude that the APP sensor assembly is defective and needs to be replaced.