
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:
- 2005, 2006, 2007, 2008, 2009 3.5L V6 Chevrolet Malibu.
- 2005, 2006, 2007, 2008, 2009, 2010 3.5L V6 Pontiac G6.
Contents of this tutorial at a glance:
- Symptoms Of A Bad APP Sensor.
- APP Sensor Terminal Pin Out Chart.
- TEST 1: Testing The Resistance Between Terminals D And F (APP Sensor 1).
- TEST 2: Testing The Resistance Between Terminals E And F (APP Sensor 1).
- TEST 3: Testing The Resistance Between Terminals E And D (APP Sensor 1).
- TEST 4: Testing The Resistance Between Terminals A And C (APP Sensor 2).
- TEST 5: Testing The Resistance Between Terminals A And B (APP Sensor 2).
- TEST 6: Testing The Resistance Between Terminals B And C (APP Sensor 2).
- Where To Buy The APP Sensor Assembly And Save.
- More 3.5L V6 Chevy Malibu Tutorials.
You can find this tutorial in Spanish here: Cómo Probar El Sensor APP (2007-2009 3.5L Chevrolet Malibu y Pontiac G6) (at: 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:
- Accelerator Pedal Position Sensor Basics (2007-2009 3.5L Chevy Malibu And Pontiac G6).
- Electronic Throttle Body Tests (2007-2009 3.5L Chevrolet Malibu And Pontiac G6).
- Throttle Body (TAC) Circuit Wiring Diagram (2007-2009 3.5L Malibu).
- 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:
- The check light engine light will be lit up by one of the following trouble codes:
- P2120: Accelerator Pedal Position (APP) Sensor 1 Circuit.
- P2122: Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage.
- P2123: Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage.
- P2125: Accelerator Pedal Position (APP) Sensor 2 Circuit.
- P2127: Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage.
- P2128: Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage.
- P2138: Accelerator Pedal Position (APP) Sensor 1 - 2 Correlation.
- Your Chevy Malibu (Pontiac G6) will run in Reduced Engine Power mode.
- The engine starts and runs but when you try to accelerate your Chevy Malibu (Pontiac G6), it accelerates very slowly.
- The engine starts and runs but the engine does not accelerate when you step on the accelerator pedal.
- 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

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)

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
Disconnect the APP sensor assembly from its electrical connector.
- 2
Place your multimeter in Ohms mode.
- 3
Connect the red multimeter test lead to terminal D.
- 4
Connect the black multimeter test lead to terminal F.
- 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.