TEST 2: Testing The DPFE EGR Flow Signal
Now we're gonna' verify that the DPFE Pressure Sensor is responding to EGR flow into the intake manifold.
Let's get started:
- With the vacuum pump still connected to the EGR valve.
- Attach the RED lead of the multimeter (using an appropriate tool) to the wire labeled with the number 1 in the image viewer that corresponds to the type of DPFE sensor installed on your vehicle.
- Connect the BLACK lead of the multimeter to a good ground point on the engine or to the battery negative terminal.
- Select Volts DC on your multimeter.
- Have an assistant crank up the car (or truck).
- Once the engine has started, notice what the reading is on your multimeter (it should be a value around .9 volts).
- After taking note of the voltage value on your multimeter, apply vacuum with the vacuum pump.
- As you apply vacuum, the engine should, once again, start to immediately idle very rough and possibly stall.
- Now notice the readings on your multimeter as you apply and release vacuum with your vacuum pump.
Now, if the DPFE sensor is working correctly, you'll notice that the voltage reading on your multimeter will increase (to about 3 Volts DC or as high as 4.5 Volts DC) whenever you apply vacuum with the vacuum pump (and of course the engine will idle rough). The voltage will decrease back to the original value recorded at idle and engine idle will return to normal when you release the vacuum applied by the vacuum pump.
Let's find out what your test results mean:
CASE 1: If the voltage reading on the multimeter increased as you applied vacuum with the vacuum pump and decreased when you released the vacuum, then the DPFE sensor is working correctly. The next step is to verify/check the EGR Valve Vacuum Regulator Solenoid. Go to: TEST 4: Testing The EGR Vacuum Regulator Solenoid (Part 1).
CASE 2: If the voltage reading on the multimeter DID NOT increase as you applied vacuum with the vacuum pump and DID NOT decrease when you released the vacuum, then the DPFE sensor is BAD. Replacing the DPFE sensor should solve the EGR fault code issue that is lighting up your check engine light (CEL) on your instrument cluster.
CASE 3: If NO voltage reading at all was displayed on the multimeter as you applied vacuum with the vacuum pump and released it. The next step is to verify that the DPFE sensor is receiving the 5V Reference voltage from the PCM (Powertrain Control Module=Fuel Injection Computer). Go to: TEST 7: Testing The DPFE 5 V REFERENCE SIGNAL.
TEST 3: Bench Testing The EGR Valve
This test step is done with the EGR valve off of the engine. The EGR valve may be hot, so be careful.
The purpose of this test is to verify that when vacuum is applied to the EGR valve, the EGR valve's pintle actually opens and closes. You'll need to blow compressed air thru the inlet opening of the EGR valve, or if you don't have access to compressed air, you can use the ‘good ole’ lungs by blowing air with your mouth.
- Remove the EGR valve from the engine.
- Connect the vacuum pump once again to the EGR valve using a piece of vacuum hose (see photos in image viewer).
- Once the vacuum pump is set up, apply vacuum.
- and apply compressed air to the inlet opening of the EGR valve.
Let's analyze your test result:
CASE 1: If you were able to blow compressed air thru' the EGR valve's inlet opening to its outlet side (which is the intake manifold side) when you applied vacuum with the vacuum pump: then the EGR valve's inlet and outlet passages are not blocked with carbon build-up. The next step is to visually check the EGR inlet orifice on the intake manifold to see that it's not blocked with carbon build-up.
If carbon build-up/blockage exists on the EGR inlet orifice on the intake manifold, clean/remove it. Re-install the EGR valve and re-test starting at TEST 1 again.
CASE 2: If you WERE NOT able to blow compressed air thru' the EGR valve's inlet opening to its outlet side (which is the intake manifold side) when you applied vacuum with the vacuum pump: The EGR valve's inlet and outlet passages are blocked with carbon build-up or the EGR valve is BAD. Visually check it for carbon build-up/blockage and if blockage exists; clean and/or remove the carbon build-up. If no carbon build-up exists, then the EGR valve is BAD, replace it.