Electronic Throttle Body Tests (2002-2007 4.2L Chevrolet TrailBlazer)

TEST 2: TPS 1 Resistance Test (Part 2 Of 2)

In this test section, we'll test the resistance between terminal A and terminal G as we open and close the throttle plate.

If everything is OK between these two terminals, you should see the resistance value increase as you open the throttle plate.

As you close the throttle plate, the resistance value should decrease.

Also, the resistance values should increase/decrease as you open/close the throttle plate without any gaps in the reading.

If TPS 1 is defective, you'll see that the resistance reading does not increase as you open/close the throttle plate or see gaps in the 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 A.
   
   NOTE: All connection are done on the male terminals of the connector of the throttle body itself.

4. 4

   Connect the other multimeter test lead to terminal G.
   
   At this point I usually get a reading between 2K to 3K Ohms from a good TPS 1.

5. 5

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

6. 6

   The resistance value should increase as you open the throttle plate.
   
   At WOT I usually see a reading between 4K to 5K Ohms from a good TPS 1.

7. 7

   Slowly close the throttle plate to its closed position.

8. 8

   The resistance value should decrease 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 decrease as you completely close the throttle plate.
    
    At this point (the throttle plate pushed down and completely closed) I generally get a reading between 1K to 2K Ohms from a good TPS 1.

Let's examine your test results:

CASE 1: The resistance increased/decreased without any gaps. This is the correct test result and it lets you know that TPS 1 is OK (not defective).

The next test is to test the resistance of terminals H and B of TPS 2. Go to: TEST 3: TPS 2 Resistance Test (Part 1 Of 2).

CASE 2: The multimeter DID NOT register the indicated resistance values. This lets you know that TPS 1 is bad. You'll need to replace the throttle body unit.

TEST 3: TPS 2 Resistance Test (Part 1 Of 2)

Testing TPS 2 follows pretty much the same procedure as testing TPS 1. The difference is that we'll perform our resistance test on different terminals.

To get our TPS 2 troubleshooting test on the way, we'll test the resistance between terminal B and terminal H.

Terminal B receives Ground, and terminal H receives 5 Volts. Both Ground and the 5 Volts come from the fuel injection computer.

If everything is okay between these two terminals, you'll see a continuity reading on your multimeter.

If there's a problem between these two terminals, you'll see a reading that indicates either a short-circuit or open-circuit problem.

If there's an open-circuit problem, you'll see a no-continuity reading from your multimeter. If there's a short-circuit problem, you'll see a resistance reading of less than 1 Ohm on your multimeter.

NOTE: All tests are done on the connector on the throttle body itself. This connector has male spade terminals.

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 the red multimeter test lead to terminal B.

4. 4

   Connect the black multimeter test lead to terminal H.

5. 5

   Your multimeter should read continuity.
   
   At this point I have gotten around 2K Ohms from a good TPS 2.

Let's examine your test results:

CASE 1: The multimeter registered continuity between terminals B and H. This is the correct test result.

The next step is to test TPS 2 while you open and close the throttle plate. For this test go to: TEST 4: TPS 2 Resistance Test (Part 2 Of 2).

CASE 2: The multimeter registered 0 Ohms between terminals B and H (or a value very close to it). This test result indicates that circuit B and H have a short-circuit problem.

With this test result you can conclude that the electronic throttle body is defective and needs replacement.

CASE 3: The multimeter reports no continuity between terminals B and H (the letters OL are displayed). This test result indicates that circuit B and H have an open-circuit problem.

With this test result you can conclude that the electronic throttle body is defective and needs replacement.