This test is a continuation of TEST 7... and here you're gonna' test the ground return circuit of the DPFE sensor.
This ground (for the 5 V REFERENCE Signal) is provided by the PCM, so it's crucial that you take the utmost care not to short this circuit to 12 volts as your are testing/verifying it. Use a multimeter for this test and not a test light.
CASE 1: If your multimeter registered 10-12 Volts: This indicates that the PCM is providing a DPFE sensor ground to the DPFE sensor. If you have gotten to this test by following the following flow of testing: TEST 1, then TEST 2, then TEST 7... then this result indicates that the DPFE sensor is BAD. Replace the DPFE sensor.
CASE 2: If your multimeter DID NOT register 10-12 Volts: Re-check all of your connections and repeat the test. The DPFE sensor will not work without this ground (that the PCM provides) and will set an EGR fault code that will light up the check engine light (CEL) on your instrument cluster. Repairing the issue of this missing ground should solve your EGR valve fault code.
It's very rare for the DPFE Sensor to have any type of issue with its Ground Return Circuit. But if you do encounter this condition and you have triple-checked all of your multimeter's connections and set-up, then the two most likely causes are:
Testing the two above conditions are beyond the scope of this article, but at least you have eliminated the EGR valve, the DPFE sensor, and the EGR Vacuum Regulator Solenoid as the cause of the EGR valve system malfunction.
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