How To Test The EGR Valve (1996-1998 2.2L Chevrolet S10, GMC Sonoma)

TEST 6: EGR Solenoid Resistance Test

It's not uncommon for the EGR valve's solenoid to wear out and suffer an open-circuit or short-circuit problem.

We can easily determine if the solenoid has suffered such a condition by testing its internal resistance with a multimeter.

If the solenoid has suffered an internal short-circuit problem, you'll see a resistance reading of 0 Ohms.

If the solenoid has suffered an open-circuit problem, you'll see a resistance value in the thousands of Ohms or the letters OL displayed on your multimeter (digital).

IMPORTANT: The EGR valve has to be at ambient temperature to get an accurate test result. If the EGR valve is hot, let it cool down completely.

NOTE: This test is done on the male spade terminals of the EGR valve itself and NOT on the female terminals of its 5-wire connector.

These are the test steps:

1. 1

   Place your multimeter in Ohms mode.

2. 2

   Disconnect the EGR valve from its pigtail connector.

3. 3

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

4. 4

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

5. 5

   The multimeter should read 8 to 9 Ohms.

Let's interpret your test results:

CASE 1: The multimeter registered the indicated Ohms value. This is the correct and expected test result.

Your next step is to remove the EGR valve and check for carbon build-up on the EGR valve itself and the EGR valve pipe's inlet. Go to: TEST 7: Checking For Carbon Build Up.

CASE 2: The multimeter DID NOT register the indicated Ohms value. This test result confirms the EGR valve is bad. Replace the EGR valve.

TEST 7: Checking For Carbon Build Up

Sooner or later, the black soot floating in the exhaust will accumulate on the EGR valve's pintle. This carbon build-up will eventually cause the EGR valve's pintle to become stuck 'open' or 'closed.'

This buildup of carbon particles will also clog the pipe (see photo 2 of 2) that connects the EGR valve to the intake manifold. It doesn't happen overnight, but it will.

So your next step is to remove the EGR valve and inspect for carbon buildup blocking the pintle and/or clogging its two orifices (ports).

You'll also check the EGR valve's pipe inlet to see if it's blocked with carbon buildup.

Let's begin:

1. 1

   Remove the EGR valve from its place on the engine.

2. 2

   Check that the EGR valve pintle is not held open carbon build up.

3. 3

   Check that the EGR valve pipe's inlet is not blocked with carbon buildup.

Let's interpret your test results:

CASE 1: The EGR valve's pintle and the pipe's inlet ARE NOT blocked with carbon. This is the correct test result.

All of the tests you've performed up to this point have not found any problems with the EGR valve. I suggest one last test. Go to: TEST 8: Checking For Clogged EGR Passages In The Intake Manifold.

CASE 2: Both the EGR valve's pintle and EGR valve pipe's inlet are blocked with carbon. Your next step is to remove the carbon deposits.

Once the carbon has been removed, verify the EGR pintle can completely close on its seat.

Re-install the EGR valve, clear the EGR valve fault codes (that were lighting up the check engine light) and road test the vehicle to see if the problem is solved.

CASE 3: Only the EGR valve's pintle was blocked with pieces of carbon from fully closing on its seat. This condition allows exhaust gas to enter the intake manifold at all times, causing a rough idle and/or engine stall problem.

Remove the carbon blocking the EGR valve's pintle. Re-install the EGR valve, clear the EGR valve fault codes (that were lighting up the check engine light), and road test the vehicle to see if the problem is solved.

CASE 4: Only the EGR valve's pipe orifice was blocked/closed off with carbon. This blockage will not allow the flow of exhaust gas into the intake manifold.

Your next step is to remove the EGR valve's pipe from the intake manifold and clean/remove the carbon.

Once the pipe has been cleaned, re-install the EGR valve, clear the EGR valve fault codes (that were lighting up the check engine light [CEL]), and road test the vehicle to see if the problem is solved.

TEST 8: Checking For Clogged EGR Passages In The Intake Manifold

Up to this point, all the tests you've performed have exonerated the EGR valve itself as the cause of the EGR system diagnostic trouble code.

There's a good chance that the EGR valve's pipe (see photo above) is clogged (blocked) with carbon buildup and causing the EGR valve diagnostic trouble code.

You can check for this condition with a specific test: start the engine with the EGR valve removed from its place (on the EGR tube adapter) and see how the engine idles.

Let's start:

1. 1

   Remove the EGR valve from its place on the engine.

2. 2

   Start the engine.

3. 3

   You'll notice one of two things:
   
   1.) The engine will start and run smoothly (as if the EGR valve where still there in its place).
   
   2.) The engine will start and idle extremely high and/or stall immediately.

4. 4

   If the engine starts and idles very very high, have your helper immediately turn off the engine.

Let's interpret your test results:

CASE 1: The engine started and idled smooth. This result confirms one of two things:

• The exhaust gas inlet (orifice) inside the intake manifold manifold is blocked with carbon.
• The pipe connecting the EGR valve to the intake manifold is blocked with carbon (the orange arrow in the photo above points to this pipe).

You'll need to remove the pipe and intake manifold to clean/remove this carbon build up blocking the EGR passages.

CASE 2: The engine started and idled very high and/or stalled. This confirms that the EGR passages inside the pipe and plenum ARE NOT clogged.