As you're probably already aware, TPS 1, TPS 2, and the TAC motor comprise the electronic throttle body on the 4.2L Oldsmobile Bravada and Buick Rainier.
The cool thing is you can accurately test each of those three components with a multimeter, and this tutorial will explain how to step-by-step.
Contents of this tutorial at a glance:
- Symptoms Of A Bad Electronic Throttle Body.
- Electronic Throttle Body Terminal Pin Out Chart.
- Where To Buy The Electronic Throttle Body And Save.
- TEST 1: TPS 1 Resistance Test (Part 1 Of 2).
- TEST 2: TPS 1 Resistance Test (Part 2 Of 2).
- TEST 3: TPS 2 Resistance Test (Part 1 Of 2).
- TEST 4: TPS 2 Resistance Test (Part 2 Of 2).
- TEST 5: Testing The TAC Motor.
- More 4.2L Oldsmobile Bravada And Buick Rainier Tutorials.
APPLIES TO: This tutorial applies to the following vehicles:
- 4.2L Buick Rainier: 2004, 2005, 2006, 2007.
- 4.2L Oldsmobile Bravada: 2002, 2003, 2004.
WIRING DIAGRAMS: The TAC system wiring diagrams can be found 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 Electronic Throttle Body
As I mentioned at the beginning of the tutorial, the electronic throttle body incorporates three components:
- TPS 1.
- TPS 2.
- Throttle actuator (TAC) motor.
TPS 1 and 2 inform the fuel injection computer of the throttle plate angle. The TAC motor opens/closes the throttle plate per the PCM commands.
Since the electronic throttle body is a critical component of the engine's management system, when one of its throttle position sensors fails, you'll see one or more of the following trouble codes:
- P0121: Throttle Position Sensor (TPS) Sensor 1 Performance.
- P0122: Throttle Position Sensor (TPS) Sensor 1 Circuit Low Voltage.
- P0123: Throttle Position Sensor (TPS) Sensor 1 Circuit High Voltage.
- P0222: Throttle Position Sensor (TPS) Sensor 2 Circuit Low Voltage.
- P0223: Throttle Position Sensor (TPS) Sensor 2 Circuit High Voltage.
- P2135: Throttle Position Sensor (TPS) Sensor 1 And 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 the vehicle accelerates very slowly (when stepping on the accelerator pedal).
- 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.
Electronic Throttle Body Terminal Pin Out Chart
| Pin | Wire Color | Description |
|---|---|---|
| A | Dark green (DK GRN) | TPS 1 Signal |
| B | Light blue with black stripe (LT BLU/BLK) | 5 Volts (TPS 2) |
| C | Black (BLK) | Ground (TPS 1) |
| D | Purple (PPL) | TPS 2 Signal |
| E | Yellow (YEL) | Throttle Actuator Motor Control |
| F | Brown (BRN) | Throttle Actuator Motor Control |
| G | Grey (GRY) | 5 Volts (TPS 1) |
| H | Black with white stripe (BLK/WHT) | Ground (TPS 2) |
The connector on the throttle body itself has male spade terminals. The terminals on the electrical connector are female terminals.
You'll perform all of the tests (in this tutorial) on the male spade terminals of the throttle body's connector and not on the female terminals of the engine wiring harness connector.
Where To Buy The Electronic Throttle Body And Save
The following links will help you comparison shop for the electronic throttle body for the 4.2L Oldsmobile Bravada and Buick Rainier:
Not sure if the electronic throttle body 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: TPS 1 Resistance Test (Part 1 Of 2)
We'll start off by testing the continuity between male terminals C and G (of the electronic throttle body itself). These two terminals belong to TPS 1.
If all is good between these two terminals, your multimeter should report continuity.
If there's a problem in the circuit, your multimeter will report:
- A short-circuit problem (an Ohms reading less than 1 Ohm).
- An open-circuit problem (a reading of OL -Open Loop).
If your multimeter registers continuity in the circuit, you'll move on to TEST 2.
NOTE: You'll make all your multimeter connections on the male spade terminals of the electronic throttle body itself.
TIP: I recommend you connect the multimeter test leads to the male spade terminals with jumper wires that have alligator clips on both ends.
These are the test steps:
- 1
Disconnect the throttle body from its electrical connector.
- 2
Place your multimeter in Ohms mode.
- 3
Connect the red multimeter test lead to terminal C.
- 4
Connect the black multimeter test lead to terminal G.
- 5
Your multimeter should read continuity.
At this point I have gotten about 3 K Ohms from a good TPS 1.
Let's examine your test results:
CASE 1: The multimeter registered continuity between terminals C and G. This is the correct test result.
So far, so good. The next test is a resistance test between terminals A and G as you open and close the throttle plate: TEST 2: TPS 1 Resistance Test (Part 2 Of 2).
CASE 2: The multimeter registered 0 Ohms (or a value very close to it) between terminals C and G. This test result indicates a short-circuit problem between terminals C and G.
With this test result, you can conclude the electronic throttle body is defective and needs replacement.
CASE 3: The multimeter reports no continuity between terminals C and G (the letters OL are displayed). This test result indicates an open-circuit problem between terminals C and G.
With this test result, you can conclude the electronic throttle body is defective and needs replacement.
