How to

How to adapt a low-pressure EGR valve

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Here we’re looking at how to adapt a low-pressure EGR valve after it’s been placed in a diesel vehicle.

The process is straightforward enough, but you’ll need your Delphi BlueTech diagnostic tool handy.

We walk you through the correct procedure step by step, from checking for fault codes to a final road test.

In this video we’ll show you how to:

Check for fault codes in the engine ECU

Use the software
Check and clear any errors
Complete a dynamic road test, and recheck the ECU

Emissions Vehicle Electronics & Engine Management How to Technicians 1 min read

What is an EGR valve, and what does it do?

The exhaust gas recirculation valve, or EGR valve for short, recirculates finely metered quantities of exhaust gas to the engine intake system. This delivers increased engine efficiency, reduced fuel consumption and lower NOx emissions.

What can cause an EGR valve to fail?

EGR valves operate in a hostile environment. Over time, they’ll experience wear and tear. The single biggest cause of failure, though, is the buildup of carbon particles from the exhaust gases along the EGR and intake system passages. Over time this will clog tubes, exhaust gas channels and eventually the valve’s plunger mechanism, causing it to either stick open or close. Failures can also be caused by a rupture or leak in the valve diaphragm.

How can you recognize a failing EGR valve?

Look out for these symptoms:

Check engine light: as with most engine management components, a problem with the EGR valve may trigger the check engine light.
Engine performance: if the valve is stuck open, the vehicle’s air-fuel ratio will be disrupted causing engine performance issues such as reduced power, poor acceleration and rough idle. It may also produce turbo boost pressure leaks, causing the turbo to work harder.
Increased NOx emissions: when the EGR valve remains shut, the high temperatures in the combustion chamber that result will leave a lot of unburned fuel in the exhaust, leading to increased NOx emissions and reduced fuel efficiency.
Engine knock: the higher temperatures and NOx may also result in increased detonation or knock. You’ll be able to hear this as a knocking noise in the engine.

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