This tutorial will explain how to test the accelerator pedal position (APP) sensors with a multimeter (no expensive diagnostic test equipment needed).
Your test results will help you determine if APP sensor 1 or APP sensor 2 is good or bad.
Contents of this tutorial:
- 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 4.2L Oldsmobile Bravada And Buick Rainier Tutorials.
APPLIES TO: This tutorial applies to the following vehicles:
- 4.2L Oldsmobile Bravada: 2004.
- 4.2L Buick Rainier: 2004, 2005, 2006, 2007.
WIRING DIAGRAM: You can find the APP sensor assembly wiring diagrams here:
- TAC System Wiring Diagram (2002-2004 4.2L Oldsmobile Bravada, 2004-2005 4.2L Buick Rainier).
- TAC System Wiring Diagram (2006, 2007 4.2L Buick Rainier).
Symptoms Of A Bad APP Sensor
As you're probably already aware, the accelerator pedal position (APP) sensors inform the fuel injection computer how much you step on or step off the accelerator pedal.
Since the APP sensors are constantly monitored by the PCM, when they fail the PCM will set one 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 Oldsmobile Bravada or Buick Rainier will run in Reduced Engine Power mode.
- The engine starts and runs but when you try to accelerate your vehicle, 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 |
|---|---|---|
| A | Purple (PPL) | Sensor Ground |
| B | Light blue (LT BLU) | APP Sensor 2 Signal |
| C | Tan (TAN) | 5 Volts |
| D | Brown (BRN) | Ground |
| E | Dark blue (DK BLU) | APP sensor 1 Signal |
| F | White with black stripe (WHT/BLK) | Sensor Ground |
For a more detailed look at APP sensor 1 and APP sensor 2 circuits, check out the TAC system wiring diagram here:
- TAC System Wiring Diagram (2002-2004 4.2L Oldsmobile Bravada, 2004-2005 4.2L Buick Rainier).
- TAC System Wiring Diagram (2006, 2007 4.2L Buick Rainier).
Where To Buy The Accelerator Pedal Assembly And Save
The following links will help you comparison shop for the accelerator pedal position sensor assembly:
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)
All right, to get started we'll test the circuit between male spade terminals D and F (see the illustration above).
Your multimeter should report continuity if the circuit between terminals D and F is OK.
Specifically, your multimeter should report a resistance value somewhere around 3K to 4K Ohms.
If there's a problem with the circuit, you'll usually see your multimeter report a short-circuit or an open-circuit problem.
NOTE: Connecting the multimeter to the indicated terminals can be challenging while the accelerator pedal assembly is bolted in place. I recommend removing the accelerator pedal assembly to quickly and easily connect your multimeter test leads to the indicated terminals.
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 D.
- 4
Connect the other multimeter test lead to terminal F.
- 5
Your multimeter should read continuity.
You should see an Ohms value around 3K to 4K Ohms.
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 testing the resistance of APP sensor 1 as you depress/release the accelerator pedal. 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) between terminals D and F. This test result confirms a short-circuit problem between terminals D and F.
With this test result, you can conclude the accelerator pedal assembly is defective and needs replacement.
CASE 3: The multimeter reports no continuity (the letters OL are displayed) between terminals D and F. This test result confirms an open-circuit problem between terminals D and F.
With this test result, you can conclude the accelerator pedal assembly is defective and needs replacement.
