In this tutorial, you'll learn how to test the accelerator pedal position (APP) sensor on the 2004-2006 2.8L Chevrolet Colorado and GMC Canyon.
All of the tests are done with a multimeter and the steps are explained in a step-by-step manner.
Contents of this tutorial at a glance:
- Symptoms Of A Bad APP Sensor.
- APP Sensor Terminal Pin Out Chart.
- Where To Buy The APP Sensor Assembly And Save.
- TEST 1: APP Sensor 1 Resistance Tests (1 Of 2).
- TEST 2: APP Sensor 1 Resistance Tests (2 Of 2).
- TEST 3: APP Sensor 2 Resistance Tests (1 Of 2).
- TEST 4: APP Sensor 2 Resistance Tests (2 Of 2).
- More 2.8L Chevrolet Colorado (GMC Canyon) Tutorials.
You can find this tutorial in Spanish here: Cómo Probar El Sensor APP 1 y APP 2 (2004-2006 2.8L Chevrolet Colorado, GMC Canyon) (at: autotecnico-online.com).
WIRING DIAGRAM: The following TAC system wiring diagram may come in handy: TAC APP Sensor Wiring Diagram (2004-2006 2.8L Chevrolet Colorado, GMC Canyon).
Symptoms Of A Bad APP Sensor
The APP sensors on your Chevrolet Colorado or GMC Canyon are monitored by the fuel injection computer the entire time the engine is running.
This means that when they fail, the computer will set an APP sensor diagnostic trouble code and illuminate check engine light.
You'll see one or more of the following diagnostic 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.
You'll also see one or more of the following symptoms:
- Your Chevrolet Colorado (GMC Canyon) will run in Reduced Engine Power mode.
- The engine starts and runs but when you try to accelerate your Chevrolet Colorado (GMC Canyon), 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.
APP Sensor Terminal Pin Out Chart
| Pin | Wire Color | Description |
|---|---|---|
| 1 | Purple (PPL) | Sensor Ground |
| 2 | White with black stripe (WHT/BLK) | 5 Volts |
| 3 | Dark blue (DK BLU) | APP Sensor 1 Signal |
| 4 | Brown (BRN) | Sensor Ground |
| 5 | Tan (TAN) | 5 Volts |
| 6 | Light Blue (LT BLU) | APP Sensor 1 Signal |
For a more detailed look at the APP sensor 1 and APP sensor 2 circuits, check out the TAC system wiring diagram here: TAC APP Sensor Wiring Diagram (2004-2006 2.8L Chevrolet Colorado, GMC Canyon).
Where To Buy The Accelerator Pedal Assembly And Save
If you find that APP sensor 1 or APP sensor 2 is defective, you'll need to replace the entire accelerator pedal assembly. The following links will help you comparison shop for the APP sensor assembly for the 2.8L Chevrolet Colorado (GMC Canyon):
Not sure if the APP sensor assembly will fit your particular GM vehicle? Don't worry, once you get to the site, they'll make sure it fits. If it doesn't, they'll find you the right one.
TEST 1: APP Sensor 1 Resistance Tests (1 Of 2)
We'll start off by testing the continuity between terminals 2 and 4 of the APP sensor assembly.
If your multimeter does not report an open-circuit or a short-circuit problem, you can move on to TEST 2.
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 2.8L Chevrolet Colorado (GMC Canyon).
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
Disconnect the APP sensor assembly from its electrical connector.
- 2
Place your multimeter in Ohms mode.
- 3
Connect one multimeter test lead to terminal 2.
- 4
Connect the other multimeter test lead to terminal 4.
- 5
Your multimeter should read continuity (around 1K to 2K Ohms).
Let's examine your test results:
CASE 1: The multimeter registered continuity between terminals 2 and 4. 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 registered 0 Ohms (or a value very close to it). This test result confirms a short-circuit problem between terminals 2 and 4.
With this test result, you can conclude that the accelerator pedal assembly is defective and needs replacement.
CASE 3: The multimeter reports no continuity (the letters OL are displayed). This test result confirms an open-circuit problem between terminals 2 and 4.
With this test result, you can conclude that the accelerator pedal assembly is defective and needs replacement.
