Hi, I'm wondering if someone can help me with this. I've been getting a P0401 code on and off for the last 2 months. I have a hybrid civic 1.4 petrol with the 8 plugs. I tried a new generic egr valve replacement but code kept returning. I'm currently on my second egr valve replacement, a second hand Siemens valve. I checked the resistances across the pins on the solenoid and they match a post that I came across online, ie, 6.5ohms across lower pins and 3.8k, 4.8k and 1.3K ohms across the top pins.
​​​I also checked the voltage from the car's solenoid and am getting around 5 volts. My questions are, 1. What should the resistances on the valve be for this car? 2. Is the voltage to the solonoid coming from the battery ok? 3. If the 5v supply to the valve is correct then what should the settings be if I use a power probe to test the valve? I really hope that someone can help me with this as I seem to be going round in circles. I tried to get the car into a Honda dealership to troubleshoot it and the soonest they can look at it is mid January and that's too late. I've spoken to several mechanics and most of them don't even know what a P0401 code is which isn't very encouraging. Any help would be much appreciated. Many thanks

 

P0401 is insufficient EGR flow.

Likely this is plugged EGR ports in the intake manifold.

 

Ok, thank you. When you say egr ports in the intake manifold are you referring to the port directly underneath the valve or deeper inside the manifold? Sorry, I'm not well up on the terminology or the mechanics. Also, what is the usual approach to clear these ports? Many thanks

 

I think that engine has an EGR plate that can be removed to clean the ports.

 

Yeah, I'm not sure I'd have the knowledge and skill to go deep into the engine and start taking things apart. I've just replaced the valve and will see how it goes over the next few days. I see people flushing out the system with a cleaner sprayed into the air intake, just wondering about trying that. Also, some people on this forum are blanking the openings of the egr valve and that doesn't seem to be an issue in terms of performance and the inference seems to be that the civic doesn't actually need an egr valve, can somebody please explain this to me?? I thought the egr system was necessary to reduce exhaust temperatures and get rid of nox emissions? I have to pass a mot every year and the emissions thresholds are quite low for that

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Cleaners sprayed in the intake aren't going to clean the EGR ports.

EGR is required especially on the hybrid. It uses a very large amount of EGR as part of how it reduces fuel consumption. They run like garbage and get poor MPGs when the EGR isn't functioning correctly.

Find someone to take the EGR plate off and clean out the carbon. It's pretty low effort and labor.

 

Ok, that's good information to know, many thanks 👍