TEST 3: 5 Volt Reference Circuit

Making Sure The EGR Pintle Position Sensor Is Getting 5 Volts. How To Test The GM EGR Valve Buick, Chevy, Olds, Pontiac Making Sure The EGR Pintle Position Sensor Is Getting 5 Volts. How To Test The GM EGR Valve Buick, Chevy, Olds, Pontiac

This test can only be accomplished with a multimeter. Do not use a test light.

You're gonna' verify that the PCM (Powertrain Control Module=Fuel Injection Computer) is providing the EGR valve's pintle position sensor with 5 Volts. It's with this voltage that the EGR valve pintle position sensor can create a return signal to the PCM.

This test can be done with the connector connected or disconnected from the EGR valve. And as always, my recommendation is to test this circuit connected and with a wire piercing probe.

  1. 1

    Place your multimeter in Volts DC mode.

  2. 2

    Probe the wire (with an appropriate tool) labeled with the letter D with red multimeter test lead (see photos in image viewer).

  3. 3

    Connect the black multimeter test lead to a good Ground point on the engine or to the battery negative (-) terminal.

  4. 4

    Turn the Key on but don't crank or start the engine.

  5. 5

    The multimeter should read 4.5 to 5 Volts.

Let's interpret your test results:

CASE 1: If the multimeter registered 5 Volts. This test result confirms that the 5 Volt Reference circuit is OK. The next step is to test for the Sensor Return circuit that the pintle position sensor (within the EGR valve) needs to be able to produce a signal. For this test, go to: TEST 4: Verifying The Ground Circuit.

CASE 2: If the multimeter DID not register 5 Volts. This confirms that there's something wrong with the circuit or the PCM could be fried (although this would be a very very rare occurrence). Without these 5 Volts, the EGR valve's pintle position sensor will not function. Repair the fault in this circuit before continuing.

TEST 4: Verifying The Ground Circuit

Making Sure The EGR Is Getting Ground. How To Test The GM EGR Valve Buick, Chevy, Olds, Pontiac Making Sure The EGR Is Getting Ground. How To Test The GM EGR Valve Buick, Chevy, Olds, Pontiac

The wire labeled with the letter B is the circuit that provides the sensor ground path for the 5 Volt Reference voltage that the PCM sends the EGR pintle position sensor in the EGR valve.

This sensor Ground is provided by the PCM within the PCM (so be careful and don't short this bad boy to power or you'll fry the PCM). In this test step, you're gonna' verify that this circuit is OK and working.

I recommend that you accomplish this test with a multimeter (don't have a digital multimeter? Need to buy one? Click here to see my recommendations: Buying A Digital Multimeter For Automotive Diagnostic Testing). Do not use a test light. This test can be done with the connector connected or disconnected from the EGR valve. And as always, my recommendation is to test this circuit connected and with a Wire Piercing Probe.

  1. 1

    Place your multimeter in Volts DC mode.

  2. 2

    Probe the wire (with an appropriate tool) labeled with the letter B with black multimeter test lead (see photos in image viewer).

  3. 3

    Connect the red multimeter test lead to the battery positive terminal.

  4. 4

    The multimeter should read 10 to 12 Volts.

Let's analyze your test result:

CASE 1: If the multimeter registered 10 to 12 Volts. Then the sensor Ground circuit is OK and doing its job.

So far, you've confirmed:

  1. In TEST 1 that the EGR pintle position signal is very low or non-existent.
  2. In TEST 3 that the EGR pintle position sensor is getting 5 Volts (power).
  3. In this test that the Ground Circuit is OK.

Taking all of the above in consideration, this means that the EGR valve's pintle position sensor is bad Since it's part of the EGR valve, you need to replace the EGR valve, this will solve your P0405 DTC.

CASE 2: If the multimeter DID not register 10 to 12 Volts. There's something wrong with the circuit. Without ground, the EGR valve's pintle position sensor will not be able to create its position signal.

So far, you've confirmed:

  1. In TEST 1 that the EGR pintle position signal is very low or non-existent.
  2. In TEST 3 that the EGR pintle position sensor is getting 5 Volts (power).
  3. In this test that the Ground Circuit is NOT OK.

This usually means a short between the PCM and the EGR's connector or a bad PCM (although a bad PCM is rare). Although testing these two things is beyond the scope of this article, you at least have eliminated the EGR valve itself as bad and now know where you need to focus your diagnostic on.