Electronic Throttle Body Tests (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier)

TEST 4: TPS 2 Resistance Test (Part 2 Of 2)

In this section, you'll test the resistance between male spade terminals B and D while manually opening and closing the throttle plate.

As you open the throttle plate, the resistance value your multimeter reports should decrease.

As you close the throttle plate, the resistance value your multimeter reports should increase.

If there's a problem between these two male spade terminals, you'll see:

• The resistance value stays stuck in one value as you open/close the throttle plate.
• Gaps in the multimeter Ohms reading as you open/close the throttle plate.

These are the test steps:

1. 1

   Disconnect the throttle body from its electrical connector.

2. 2

   Place your multimeter in Ohms mode.

3. 3

   Connect one multimeter test lead to terminal B.
   
   NOTE: You'll make all multimeter connections on the male spade terminals of the electronic throttle body itself.

4. 4

   Connect the other multimeter test lead to terminal D.
   
   At this point, I generally see a reading between 2K to 3K Ohms from a good TPS 2.

5. 5

   Slowly open the throttle plate by hand till it reaches its wide-open throttle (WOT) position.

6. 6

   The resistance value should decrease as you open the throttle plate.
   
   At wide open throttle (WOT), I usually see a reading between 900 to 1K Ohms from a good TPS 2.

7. 7

   Slowly close the throttle plate to its closed position.

8. 8

   The resistance value should increase as you close the throttle plate.

9. 9

   Gently push down and completely close the throttle plate.

10. 10

    The resistance value should continue to increase as you completely close the throttle plate.
    
    At this point (the throttle plate pushed down and completely closed) I generally get a reading between 2K to 3K Ohms from a good TPS 2.

Let's examine your test results:

CASE 1: The resistance increased/decreased without any gaps. This is the correct test result.

If TPS 2 has passed TEST 2 and TEST 3, you can conclude it's not defective.

Your last test is testing the internal resistance of the throttle actuator motor. Go to: TEST 5: Testing The TAC Motor.

CASE 2: The resistance DID NOT decrease/increase. This lets you know TPS 2 is bad. You'll need to replace the throttle actuator assembly.

TEST 5: Testing The TAC Motor

In this last test, you'll test the internal resistance of the throttle actuator (TAC) motor.

If the multimeter reports an open-circuit or short-circuit problem, the TAC motor is bad.

If the throttle actuator motor is OK, you should see a reading between 2 and 13 Ohms.

These are the test steps:

1. 1

   Disconnect the throttle body from its electrical connector.

2. 2

   Place your multimeter in Ohms mode.

3. 3

   Connect one multimeter test lead to terminal E and the other to terminal F.

4. 4

   Your multimeter should read continuity.
   
   If the resistance reading is below 1 Ohm, the motor has an internal short-circuit problem.
   
   If the resistance reading is in the K Ohms range or your multimeter reads OL, the motor has an internal open-circuit problem.
   
   The resistance reading I've gotten from good throttle actuator motors has been between 2 and 12 Ohms.

Let's examine your test results:

CASE 1: The multimeter registered continuity between terminal E and F. This is the correct test result.

If your 4.2L Oldsmobile Bravada or Buick Rainier's electronic throttle body passed TEST 1 and TEST 2, you can conclude the electronic throttle body is OK and not defective.

CASE 2: The multimeter registered 0 Ohms between terminal E and F (or a value very close to it). This lets you know the TAC motor has an internal short-circuit problem and is defective.

Replace the throttle actuator assembly.

CASE 3: The multimeter reports no continuity between terminal E and F (the letters OL are displayed). This lets you know the TAC motor has an internal open-circuit problem and is defective.

Replace the throttle actuator assembly.

More 4.2L Oldsmobile Bravada And Buick Rainier Tutorials

You can find a complete list of 4.2L Oldsmobile Bravada and Buick Rainier tutorials and wiring diagrams here:

• GM 4.2L Index of Articles.

Here's a list of articles you'll find there:

• Blown Head Gasket Tests (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier).
• How To Test Engine Compression (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier).
• TAC System Wiring Diagram (2002-2004 4.2L Oldsmobile Bravada, 2004-2005 4.2L Buick Rainier).
• How To Test The Ignition Coils (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier) .