How To Test The EGR Vacuum Solenoid (1994-1995 Chevrolet S10, GMC Sonoma)

TEST 2: Applying 12 Volts And Ground To The EGR Vacuum Solenoid

In this test section, we'll focus on bench testing the EGR vacuum solenoid.

This bench test involves applying 12 Volts and Ground to the solenoid and checking that it opens.

In its open state, it should allow air to pass from its inlet port to its outlet port.

To accomplish this test without complications, I suggest:

• You use jumper wires with insulated alligator clips.
• One of the jumper wires should have an inline fuse.

NOTE: This test is done with the EGR vacuum solenoid removed from its location on the intake manifold.

These are the test steps:

1. 1

   Connect a vacuum hose to the vacuum solenoid's inlet port.

2. 2

   Connect the red jumper wire to the terminal labeled with the letter B in the illustration above.

3. 3

   Connect the other end of the red jumper wire to the battery positive (+) post .

4. 4

   Connect the black jumper wire to the terminal labeled with the letter A.

5. 5

   Connect the other end of the black jumper wire to the battery negative (-) post.

6. 6

   The EGR vacuum solenoid should produce an audible click.

7. 7

   Blow air through the vacuum hose connected to the solenoid's inlet port.

8. 8

   The air should pass from its inlet port to its outlet port.

Let's interpret your test result:

CASE 1: The EGR vacuum solenoid activated and let air pass thru to its outlet port. This is the correct test result.

Even tho' the solenoid is activating and letting air pass thru; you need to check one more thing. Go to: TEST 3: EGR Vacuum Solenoid Resistance Test.

CASE 2: The EGR vacuum solenoid DID NOT activate and DID NOT let air pass thru to its outlet port. This test result tells you the EGR vacuum solenoid is defective and needs replacement.

TEST 3: EGR Vacuum Solenoid Resistance Test

For our last EGR vacuum solenoid test, I'll ask you to check the internal resistance of the solenoid.

This resistance test aims to see if the solenoid has suffered an internal short-circuit or open-circuit problem.

If the solenoid has an internal short-circuit problem, your multimeter will read a resistance reading of 1 Ohm or less.

If the solenoid has suffered an open-circuit problem, your multimeter will report a no-continuity reading.

These are the test steps:

1. 1

   Place your multimeter in Ohms mode.

2. 2

   Connect the red multimeter test lead to the male terminal labeled with the letter B.

3. 3

   Connect the black multimeter test lead to the male terminal labeled with the letter A.

4. 4

   Your multimeter should register a resistance value of around 20 Ohms.

Let's take a look at what your test results mean:

CASE 1: The resistance of the EGR vacuum solenoid is around 20 Ohms. This is the correct and expected test result.

NOTE: If the test result of TEST 2 confirms that the EGR valve vacuum solenoid DOES NOT open, even though its internal resistance is within the specified range, the solenoid is bad and needs replacement.

CASE 2: The resistance is not within the indicated range. With this test result, you can conclude that the EGR vacuum solenoid is bad and needs replacement.

NOTE: Even if the solenoid passed TEST 2, but its resistance is not within the indicated range, the vacuum solenoid is bad and needs replacement.