Toyota EGR valve: understanding exhaust gas recirculation valves

What is an exhaust gas recirculation (EGR) valve?

The EGR valve in your Toyota is fitted within the exhaust system and allows some of the gases produced during the combustion process to be re-burnt within the combustion chamber for a second and more effective time. This occurs when the correct engine operating conditions are met and, in turn, serves to reduce harmful emissions.

What does an EGR valve do?

The process of recirculating precise quantities of exhaust gases back into the combustion chamber has a number of advantages. In petrol engines, it helps to lower combustion temperatures and reduces the chance of spontaneous combustion, also known as knock. This allows the engine control unit (ECU) to dilute the air/fuel mixture and reduce petrol consumption.

In diesel engines, the role of the EGR valve is even more important. Routing exhaust gases back into the combustion chamber also lowers combustion temperatures, but the primary benefit is the reduced formation of nitrous oxide (NOx) particulates. In addition, the reappearance of spent exhaust gases within the combustion chamber enables the engine to neutralise these particulates through secondary burning.

Does the work of the EGR valve relate to the function of the particulate filter in diesel engines?

Yes, but indirectly. The neutralising of NOx soot within the combustion chamber reduces the quantity of this material heading into the diesel particulate filter (DPF) installed further down the exhaust system. This increases the time period between regeneration procedures and the service life of the DPF itself.

Why might an EGR valve fail?

Its location within the direct path of flowing exhaust gases means that soot can accumulate around the EGR valve and block its free movement. It is possible to mitigate this by ensuring the vehicle is regularly driven at sustained speeds above 40mph. Constant use of any vehicle in low-speed, urban environments with frequent stops will accelerate the amount of soot collecting around the EGR valve.

How can I tell if the EGR valve in my car is failing?

A failing EGR valve will affect the performance and economy of your engine, though it is likely that the ECU will notice the issue and alert the driver through a dashboard warning light before any physical symptoms are experienced. These symptoms may include rough idling, hesitance in acceleration and a loss in fuel economy.

What do I need to do if I see the engine check light illuminate?

Return the car to your main dealer to be checked. If the fault code displayed by the diagnostic equipment relates to exhaust gas recirculation, the likelihood is that the valve will need to be either cleaned or replaced. Cleaning is much cheaper than replacement, so it is prudent to react immediately to all warning lights.

129 comments

  1. Hi there a non Toyota garage has fitted a new EGR valve and air mass sensor to my Toyota Avensis T180 diesel but it is still not working. They claim to have fitted Toyota parts so what other issues can be causing the lack of power?

    1. Hi Jane,

      Impossible for us to say based on this message alone. Please contact your nearest Toyota centre so they can physically inspect the vehicle.

      Thanks

    2. I had the same issue in my Rav4 3 times they changed the EGR valve. In the end they realised that it wasn’t the EGR valve at all. It was the onboard computer software that needed updating. Once that was done I had no further problems.

  2. Dear Jane
    i have a land cruiser d4d 120 with 1kdf-tv diesel engine my check engine light comes on and fault error po400
    appears on diagnostic tool i may drive more than one hour with any problem and some times i drive for few minutes with bumpy road then i have check engine on.
    Egr is clean ,valve hold vacuum .no vacuum leak, no sensors wire is broken or failed sensor.no determined problem appears.
    please help

    1. Hi Jehad,
      Thanks for your comment.
      We would recommend taking your vehicle to a Toyota centre in your region for further assistance as we are only able to advise on UK specification vehicles.
      Thanks.

  3. My Rav 4 ran brilliantly until the EGR unit was replaced under recall notice. Since then the car has serious intermittent problems with loss of power, increased fuel consumption and stalling. The local Toyota garage that did the replacement say it’s nothing to do with them and the fault wouldn’t have been caused by the work they did and that it’s just a coincidence. RAC spent 2 hours ‘ fixing’ the problem a couple of weeks ago saying if it happens again they suspect a faulty part has been fitted. It’s happened again! Seriously fed up. Now thinking of trying to drive to the Toyota garage I bought the car from which is 60 miles away as there is no way I trust the local garage to be honest or fix the problem.

    1. Hi, SP My local garage advised me to get recall done on my service which I accepted. I just seen your message and now thinking what if I have same issue. My Rav4 was driving brilliantly so far. I have told the garage that there is no issue with my Car so far. I now Pray that nothing go wrong in any part. I will keep you posted if i come across same issue. Thank you for your message it’s very useful. Kind Regards

  4. Hi
    I have 2008 Toyota parado and I can hear knocking sound in my engine. When this happens the engine check light blinks .
    It’s not a continued knocking sound comes and goes. Engine sound in idle is ok
    What could be the reason.

    1. Hello Ritesh, thanks for your comment.

      We are only able to advise on UK vehicles. Please contact a Toyota Centre in your local area so the team there can take a look at your Prado in person.

      Thanks.

  5. Can you confirm if Toyota are failing to conduct repair work under warranty for the failure of the EGR system on Rav4 Plugin Hybrids. That is what Technical Service Bulletin EG-00691T-TME implies.

    If so how many are failing and what is the cost of a repair that you are making owners undertake please.

  6. Hello, we recently bought Toyota Auris 2015 hybrid. The car has a 1.8 gas engine and 227,000 km. We brought it to Toyota for an inspection and a battery check. It all passed.

    When the car travels between 20-60km/h and the EV light is off, we can hear a clapping sound. It is not all the time. We can only listen to it when the conditions we mentioned are met and reach a cruising speed, which means I’m very steady on the gas, usually just under the central line in the eco range. Once the noise starts, it will not go away unless I give the car gas or release the gas pedal. If I can get the EV light to come on and reach the same cruising speed, being steady on the gas, then the noise does not happen.

    We brought the car to Toyota, and while they observed and confirmed the noise, they had no idea where it was coming from. There were no errors when they connected the vehicle to a computer for diagnostic.

    After much research, we have been advised that the engine knocking is most likely due to blocked EGR, EGR cooler, EGR pipe and intake manifold.

    Is that a valid guess?

    1. Hi Elena,
      Thanks for your comment.
      Unfortunately, without physically inspecting your vehicle, we are unable to advise on this.
      We apologise that we cannot assist you further.
      Thanks.

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