I have a slight Radiator leak and a week ago my CEL came on. I thought it could be Cooling System related. I went to Auto Zone and the only code that came up is PO402. Could someone explain? I know it's something with the EGR Valve Flow. But I don't know a damn thing about fixing cars. Could my leaky Radiator somehowcause THAT code ? Again, it's a slight leak. I'm thinking one has nothing to do with the other. Any help would be appreciated. Thanks in advance.
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The coolant leak does not have anything to do with the EGR flow malfunction code Dino. Check the link below to Mazda TSB that addresses this problem on you engine. Before taking all of that apart though you will want to check and see if you have vacuum to the EGR Boost sensor solenoid valve. The information in the TSB is really only for severe cases of carbon accumulation and a cleaning of the vacuum port to the Boost sensor can often clear things up.
your always a big help. That PDF file told it all & right from Mazda. I was told by someone that there is a EGR Valve that is much more easily accesable that I could clean Carbon Deposits out of. It looks like a round black plastic cap and comes apart with 4 screws. Is that the EGR Valve ? Can cleaning that solve my problem possibly ? As usual, I know nothing about all this so bare with me.
Does kind of sound like the electical motor actuator portion of the EGR valve that you are talking about with the black cap and four screws but do not think you should need to take that apart. Run a big risk of damaging the motor assembly when it is perhaps not needed.
First diagram below is of the EGR valve. Not a very good one but best I could locate.It is located just below and to the rear of your throttle body (the throttle body by the way is the part that the black, flexible, accordian tube from the air cleaner attaches to). The picture in the TSB is also showing where the outlet port inside the intake is and inlet port at the EGR valve.
The system could be working just fine but the computer does not 'see' it because the EGR boost sensor is not getting any vacuum. In the second diagram, the two parts in the right rear corner of engine compartment are the EGR boost sensor and the boost sensor solenoid valve. This is the sensor that the engine computer uses to determine if the EGR is operating correctly. The boost sensor and solenoid will be connected by a short vacuum line. The solenoid valve has another line attached to it that goes to a port on the backside of the intake manifold. It is this port that very often clogs up with carbon and blocks the signal vacuum to the solenoid and sensor. Take that vacuum line carefully off of the solenoid (it is only plastic and somewhat fragile) and make sure there is a good strong vacuum from the intake manifold. If not then follow that vacuum line down the manifold and see if you have good vacuum there.Good vacuum should instantly cause the hose to stick to the end of a wetted fingertip. If still no vaccum there then you have probably found your problem. If you do have good vacuum then cleaning the ports in the intake manifold would be next step.
Last drawing is what the solenoid valve should look like just for reference.
I'm going to attempt to look @ what youwrote & obsorb it more after Dinner, but I just wanted to tell you after just fooling around & dusting off the outside of what I think is the EGR Boost Solenoid Valve (the black round cap thing), I started the car up this morning & the CEL is gone. I did nothing but touch the thing last night and dust it off. True & funny story. I was too chicken to attempt what you suggested but I'm going to reread your post & figure it out after Dinner. Thanks again. I'm sure I'll be back with Questions.
Code: PO402 EGR Flow Excessive Detected
They say: Remove EGR Valve, Check if Gasket is Good, If not, Replace Gasket. Then they list if all else fails, Replace PCM. Now what's that ?
They mention nothing about cleaning, just replacing gasket.
The picture you sent to me was in fact the EGR valve. Notice in that picture that there is a vacuum line visible that attaches to the engine right where the EGR valve is bolted on. This is the vacuum port that I would like you to remove and check for good vacuum source. Pics below are of the EGR boost sensor and solenoid valve. That vacuum line in your picture goes to here.
This is a far away view of where the sensor and solenoid are at in engine compartment
Here is a close up
This arrow is pointing to the vacuum line that comes from the intake manifold. Remove this vacuum line and make sure there is vacuum when engine is running.
Here is the pic that you sent to me of your EGR valve. The port that needs checked for vacuum is right where that vaccum line attaches, just to the right side of the black plastic cap you describe.
ok. I understand when you explained on my Picture. The only line there is the onse to check for Vacuum. While I was becoming impatient, I talked to a friend of mine from a Ford Mercury Dealership. He told be to get a can of Intake Cleaner. I used STP. Open the bigest neck house that goes to engine and with the engine running, squirt some Cleaner in the big hole and accelerate so it doesn't stall. I did it. I also filled up with Chevron High Test with the added Ingrediant theat starts with a T (Techron or something). I unplugged the battery so CEL would go away. The car seems to be running better now. It's probably just the Gas. The code will probably reapear. I sprayed about 6 good squirts in there. Engine revved up immensely the more I sprayed. I kept it at a steady rev. When it was able to idle without stalling, I turned the key off, reattached the big hose, tightened screw. Drove the Car for 15 minutes, got it washed and that's where I'm at now. I talked to my Mechanic & the Ford Mercury Friend & both said it could not harnm the car or engine. I'm just wondering if I sprayed enough. My friend suggested half a can. I thought that might be too much, so I sprayed about a quarter can in there. So what do you think ? Did I do something wrong. Again I'm not a mechanic. I had to try the easiest way for now. btw, the hose going into the EGR has that butterfly clip & I could not figure out how to undo that bugger. That's a thin line and I did not want to break it. I was also told to spray in that tiny hole where tube goes. But I chickend out.
I am you did nothing wrong Dino. Using the cleaner into the intake will help out the deposits inside the intake manifold but will unfortunately not do much for the deposits at the EGR valve as the cleaner will not even get down there with that kind of introduction method. From the other pics I enclosed in last post I hope you can now locate the EGR boost sensor and solenoid valve. When you do, you will see a very short vaccum tube between the two parts and there will be another vacuum line that heads over towards the engine. This vacuum line is the other end of the one down by the EGR valve. If you can remove that vacuum line from the solenoid in the pics, you can check for vaccum at that point. The valve nipple is plastic so be as gentle as possible in removing. Use a twisting and slight pulling motion to remove. Or you could just cut the vaccum line up by the solenoid to check and then install a straight hose line connector available from any parts store to get the line back in one piece. If you break the solenoid I will send you another one. Have 5 or 6 in my box that are identical solenoids.