How To Test APP Sensor 1 And APP Sensor 2 (2005, 2006, 2007, 2008, 2009, 2010 2.2L Chevrolet Cobalt and 2007, 2008, 2009 2.2L Pontiac G5)

This tutorial will help you test accelerator pedal position (APP) sensor 1 and sensor 2 on the 2005-2010 2.2L Chevrolet Cobalt or 2007-2009 2.2L Pontiac G5.

As you're probably already aware, two APP sensors are part of the accelerator pedal. Both are tested in the exact way and in this tutorial I'll explain how to do it.

With your test results you'll be able to find out if they are defective or not.

NOTE: This tutorial applies to the following vehicles (since they all use the exact same accelerator pedal assembly):

  1. 2005, 2006, 2007, 2008, 2009, 2010 2.2L Chevrolet Cobalt.
  2. 2007, 2008, 2009 2.2L Pontiac G5.

You can find this tutorial in Spanish here: Cómo Probar El Sensor APP 1 y 2 (2005-2010 2.2L Chevrolet Cobalt y Pontiac G5) (at: autotecnico-online.com).

NOTE: The following TAC system wiring diagram may come in handy: TAC System Wiring Diagram (2005-2009 2.2L Chevrolet Cobalt And Pontiac G5).

Symptoms Of A Bad APP Sensor

The APP sensors are tasked with informing your 2.2L Chevrolet Cobalt or 2.2L Pontiac G5's fuel injection computer with how much you step on or off the accelerator pedal.

This accelerator pedal position information is used to open the throttle plate, inject more fuel, and a host of other important things to keep the engine running optimally and correctly.

So when one of the APP sensors fails, 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 Cobalt (Pontiac G5) will run in Reduced Engine Power mode.
  3. The engine starts and runs but when you try to accelerate your Chevy Cobalt (Pontiac G5), 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.

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 (2005, 2006, 2007, 2008, 2009, 2010 2.2L Chevrolet Cobalt and 2007, 2008, 2009 2.2L Pontiac G5)

The accelerator pedal assembly's electrical connector has a total of 6 wires coming out of its electrical connector.

This is due to the fact that each APP sensor has 3 circuits: a power circuit, a Ground circuit, and an APP signal circuit.

Here's a brief description of each:

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

For a more detailed look at the APP sensor 1 and APP sensor 2 circuits, check out the TAC system wiring diagram here: TAC System Wiring Diagram (2005-2009 2.2L Chevrolet Cobalt And Pontiac G5).

TEST 1: APP Sensor 1 Resistance Tests (1 Of 2)

How To Test APP Sensor 1 And APP Sensor 2 (2005, 2006, 2007, 2008, 2009, 2010 2.2L Chevrolet Cobalt and 2007, 2008, 2009 2.2L Pontiac G5)

Testing the APP sensors simply involves a series of multimeter resistance tests. To get this show on the road we're gonna' start of by testing APP sensor 1.

We're gonna' test the resistance between terminal D and terminal F and make sure that neither an open-circuit nor a short-circuit exists between these two terminals.

If open-circuit exists between these two terminals, then your multimeter will read OL (over limit) and you can immediately conclude that APP sensor 1 is defective and the accelerator pedal assembly needs to be replaced.

If a short-circuit exists between these two terminals, then your multimeter will read a resistance of under 1 Ohm and you can immediately conclude that APP sensor 1 is defective and the accelerator pedal assembly needs to be replaced.

NOTE 1: All resistance tests are done on the male spade terminals of the accelerator pedal assembly itself. There's a good chance that to access the male spade terminal of the accelerator pedal assembly you're gonna' have to remove the accelerator pedal from your 2.2L Chevrolet Cobalt or 2.2L Pontiac G5.

NOTE 2: The easiest way to connect your multimeter's test leads to the male terminals of the APP sensor assembly is with jumper wires with alligator clips on both ends.

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 one multimeter test lead to terminal D.

  4. 4

    Connect the other multimeter test lead to terminal F.

  5. 5

    Your multimeter should read continuity.

    At this point I usually get 1.3 K Ohms for the resistance reading from a good APP 1 sensor.

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 resistance of APP sensor 1 as we depress the accelerator pedal. For this test go to: TEST 2: APP Sensor 1 Resistance Tests (2 Of 2).

CASE 2: The multimeter indicated an open-circuit or a short-circuit between terminals D and F. This lets you know that APP sensor 1 is defective within the accelerator pedal assembly.

Replace the accelerator pedal assembly.

Chevrolet Vehicles:

  • Cobalt 2.2L
    • 2005, 2006, 2007, 2008, 2009, 2010

Pontiac Vehicles:

  • G5 2.2L
    • 2007, 2008, 2009