How To Test The Electronic Throttle Body (2004-2006 2.8L Chevrolet Colorado, GMC Canyon)

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

In this test section, you'll test the resistance across terminals B and D while opening and then closing the throttle plate.

If all is OK, you should see:

• The resistance decrease as you open the throttle plate to its wide-open position.
• The resistance increase as you close the throttle plate from its wide-open position to its closed position.

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.

4. 4

   Connect the other multimeter test lead to terminal D.
   
   NOTE: You'll make all multimeter connections on the male spade terminals of the electronic throttle body itself.
   
   At this point, you'll see a reading somewhere around 2K Ohms.

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.

7. 7

   Slowly close the throttle plate to its fully closed position.

8. 8

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

Let's examine your test results:

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

Your next step is to go to: TEST 5: Testing The TAC Motor.

CASE 2: The resistance DID NOT decrease. This lets you know that TPS 2 is bad.

Replace the electronic throttle body.

CASE 3: The resistance DID NOT increase. This lets you know that TPS 2 is bad.

Replace the electronic throttle body.

CASE 4: The resistance DID NOT decrease/increase. This lets you know that TPS 2 is bad.

Replace the electronic throttle body.

TEST 5: Testing The TAC Motor

If you've reached this test section, you have:

• Confirmed that TPS 1 is OK (TEST 1 and TEST 2).
• Confirmed that TPS 2 is OK (TEST 3 and TEST 4).

You'll test the resistance across terminals E and F of the throttle actuator motor for your last test.

This test will determine if the motor has suffered an internal short-circuit or open-circuit problem, to be a bit more specific.

If the throttle actuator motor has an internal short-circuit problem, you'll see a resistance reading below 1 Ohm.

Suppose the throttle actuator motor has an internal open-circuit problem. In that case, you'll see a resistance reading in the thousands (K) of Ohms or the letters OL (if you're using a digital multimeter).

Let's get started:

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.

4. 4

   Connect the other multimeter test lead to terminal F.

5. 5

   Your multimeter should read continuity.
   
   If the resistance reading is 0 Ohm, then the motor has an internal short-circuit problem.
   
   If the resistance reading is in the K Ohms range or your multimeter reads OL, then 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 2004-2006 2.8L Chevrolet Colorado (GMC Canyon)'s electronic throttle body passed TEST 1 and TEST 2, then you can conclude that the electronic throttle body is OK and not defective.

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

Replace the throttle actuator assembly.

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

Replace the throttle actuator assembly.

More 2.8L Chevrolet Colorado (GMC Canyon) Tutorials

You can find a complete list of 2.8L Chevrolet Colorado (GMC Canyon) tutorials and wiring diagrams here:

• GM 2.8L Vortec 4-Cylinder Index of Articles.

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

• How To Test Engine Compression (2004-2006 2.8L Chevrolet Colorado, GMC Canyon).
• APP Sensor Tests (2004-2006 2.8L Chevrolet Colorado, GMC Canyon).
• Blown Head Gasket Tests (2004-2006 2.8L Chevrolet Colorado, GMC Canyon).
• TAC Throttle Body Wiring Diagram (2004-2006 2.8L Chevrolet Colorado, GMC Canyon).