How To Test APP Sensor 1 And 2 (2004-2007 4.2L Chevrolet TrailBlazer)

TEST 4: APP Sensor 2 Resistance Tests (2 Of 2)

In this test section you're going to test the resistance between terminal B and terminal C as you depress/release the accelerator pedal.

If APP sensor 2 is working correctly your multimeter will report a resistance value that increases as you depress the pedal. Once you release the pedal, the resistance value should decrease back to the value you saw at the beginning.

If APP sensor 2 is defective your multimeter will report a resistance value that'll stay stuck at one number as you depress/release the pedal.

Or the resistance value will show gaps in the reading as you depress/release the pedal.

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 B and the other test lead to terminal C.
   
   At this point I generally see a resistance reading of about 730 Ohms (0.7 K Ohms) from a good APP sensor 2.

4. 4

   Slowly depress the pedal by hand till it bottoms out.
   
   The resistance value should increase
   
   With the pedal fully depressed I generally see a resistance reading of about 3 K Ohms from a good APP sensor 2.

5. 5

   Slowly release the accelerator pedal.
   
   The resistance value should decrease back to the original value (or close to it) that you saw in step 3.

Let's examine your test results:

CASE 1: The resistance decreased/increased smoothly and without gaps as you depressed/released the accelerator pedal. This test result confirms that APP sensor 2 is working correctly.

If APP sensor 1 and APP sensor 2 have passed all the tests in this tutorial, then you can conclude that the accelerator pedal assembly does not need to be replaced.

CASE 2: The resistance DID NOT decrease/increase as you depressed/released the accelerator pedal. This test result confirms that APP sensor 2 is defective.

Since APP sensor 2 is part of the accelerator pedal assembly, you'll need to replace the entire accelerator pedal.

CASE 3: The resistance decreased/increased BUT there were gaps in the reading as you depressed/released the accelerator pedal. This test result lets you know that APP sensor 2 is defective.

Since APP sensor 2 is part of the accelerator pedal assembly, you'll need to replace the entire accelerator pedal.

More GM 4.2L Test Tutorials

If this tutorial was helpful/informative, you can find a complete list of tutorials here: GM 4.2L Index Of Articles.

Here's a sample of the tutorials you'll find there:

• How To Test For A Blown Head Gasket (2002-2009 4.2L Chevrolet TrailBlazer).
• How Often Should I Replace The Spark Plugs? (2002-2009 4.2L Chevrolet TrailBlazer).
• How To Test Engine Compression (2002-2009 4.2L Chevrolet TrailBlazer).
• Electronic Throttle Body Tests (2002-2007 4.2L Chevrolet TrailBlazer).