How To Test a Honda Civic EGR Valve

How To Test a Honda Civic EGR Valve


Your Civic EGR Valve is basically a emissions valve that recycles exhaust gases back through your combustion chamber. This regulatory valve is designed to lower harmful emissions to the atmosphere. Over time carbon build up and gunk can build up on your EGR valve and prevent it from working efficiently.

When this happens your Honda engine code will trigger a DTC trouble code and store it. Your check engine light will then turn on, and you may experience a loss of power and engine responsiveness. Today I’l be showing you how to test your Honda Civic EGR valve in a 1997 Honda Civic. Although we’ll be working on a 1997 model, you can still use this guide to test most Civics from 1992 to 2000.

This Honda Civic EGR Valve DIY tutorial is meant for the 1996-1998 models with a 1.6 liter engine in it, but as stated you can use this to test any Civic from 1992-2000. Our test vehicle is a 1997 Honda Civic HX with a manual transmission. When you want to test your Civic EGR Valve, there’s 3 components you must take a look at.

If you own a Honda Civic EG (1992-1995), the trouble code of your OBDI vehicle must be retrieved jumping the two pin connector under your dash. When your EGR valve isn’t working, this will come back as a trouble code of 12.

The Honda Civic EK or (1996-2000) is an OBDII vehicle, and will have a trouble code of P0401. If you own a OBDII Honda Civic, use a scan tool to retrieve the information from your Diagnostic Computer.

The Parts of a Honda Civic EGR Valve

When your Civic EGR Valve isn’t functioning, there’s three vital components of this system to check. The first one is the actual EGR valve, which is usually mounted to the intake manifold.

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This unit typically comes complete with the EGR pintle solenoid and the lift sensor. These parts work together to route exhaust gases back into your engine. Here’s what each one of those components do individually so you understand how your Civic EGR Valve works.

  • EGR Valve – This component opens and allows the exhaust gases to route into your intake manifold.
  • EGR Pintle Solenoid – Activates the operation of your EGR valve. This is also known as the EGR transducer, and it’s connected by a two pin connector.
  • EGR Lift Sensor – What informs your Honda Civic ECU of the real time position of your EGR valve. This is also known as the EGR position sensor.

The last part of your Honda Civic EGR system is the actual ECU or engine computer. To find your Honda Civic ECU, you will need to open your passenger side door and remove the kick panel.

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From this point you will be undoing the 10mm bolts that secure the Honda Civic ECU in place. Unplug the D ECU plug ( the furthest to the right ), and the A plug ( the furthest to the left)

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Testing for ECU continuity for your Honda Civic EGR Valve

The first section of your Honda Civic ECU we’ll start with is the D plug. This is the 16 pin connector that’s the furthest to your right if you are facing the front of the ECU plugs. You will be using a multimeter to check the wires in our Honda Civic EGR wiring diagram below.

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The pins you’ll be checking is D1, D9 and D11 as these are primary control pins for your Civic EGR Valve. The values you are checking for are below.

  • Honda Civic ECU D1 PIN – YELLOW / BLUE – 5 volts of DC power
  • Honda Civic ECU D9 PIN – WHITE / BLACK – EGR Pintle Lift Signal
  • Honda Civic ECU D11 PIN – GREEN / BLACK – Ground signal

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The next part of our Civic EGR Valve wiring schematic is the Honda Civic ECU plug shown above. This plug is the leftmost one found on your Honda Civic ECU, called the A plug. This is a 30 pin unit and the wire you will be checking is PIN 7. This is a PINK wire that’s the direct control wire for your Civic EGR Valve solenoid.

How To Test a Honda Civic EGR Valve

When checking your EGR valve lift sensor, you will see that the GREEN / BLACK wire shares a ground signal with many other sensors in your 1.6 liter engine. The YELLOW / BLUE wire that connects to the EGR lift sensor or transducer is also the same 5 volt signal that feeds your Honda Civic TPS sensor.

If you’ve checked out your EGR valve wiring and everything checks out, you may need to clean or replace your EGR valve completely. Have any questions about our How To Test guide? Leave us a comment below and let us know!!