***PLEASE DO NOT RESPOND WITH SUGGESTIONS I JUST DISABLE THE EGR. I AM NOT LOOKING FOR WAYS TO DISABLE EGR. I LEGITIMATELY WANT MY EGR SYSTEM TO WORK CORRECTLY. I KNOW HOW TO DISABLE EGR, AND I DO NOT WANT TO DO THIS***


Hello, I picked up an evo 9 GSR at the beginning of this year. The car was modified by the previous owner, and I have been putting it back to stock in an effort to get it back on the road and running properly. I have spent nearly five figures on repairing and replacing components, and the car is running really great now. The only issue I have is that I keep getting a P0401 check engine light, and am unable to set my EGR monitors as a result. Here is what I've done that directly relates to the EGR system:

I flashed the ECU with a stock tune rom. I plan to double check the exact version I flashed onto the ECU to verify it is specifically for a USDM evo ix GSR.
I've replaced the MAP sensor
I've replaced the EGR solenoid valve
I've removed the EGR valve, cleaned it with brake cleaner, applied compressed air to the lower port to visually verify the valve opens, applied vacuum to the top port to visually verify the valve opens, applied compressed air to each vacuum hose to verify they are routed correctly and flowing air, applied compressed air to the intake manifold egr ports to verify they are not clogged, and re-assembled the system and then let the car idle with the top port unplugged and applied vacuum to the top port to verify that the idle quality and speed reduces.
I grounded pin 6 on the ECU with the car running to verify that the idle quality and speed reduces.
I've put legitimate hose clamps on all of the vacuum lines for the EGR system, and none of the lines have become disconnected at any point while I have been driving the car. I used this style clamps, although off of 1g DSMs, not ebay. https://www.ebay.com/itm/281954824209

Current mods:
The previous owner said the car has kelford 272 cams, looking through the oil cap I believe this to be correct
The car has a full turbo back exhaust including o2 housing. I don't recall the brand, but it's a full system with a stock CAT.
The car has an aftermarket intercooler, with stock intercooler piping.
There is a turbo timer which appears to not be functioning and I have intended to remove but haven't got around to yet.
The car has toyota brand COP ignition

Some background information:
I've replaced the timing belt and all the typical stuff that goes with that including the water pump, and put used stock injectors in that I had cleaned at RC engineering. I also replaced o2 sensors, intercooler piping, intake pipe, boost solenoid, idle speed controller, and rebuilt the throttle body. I removed a wideband o2 sensor, snow performance meth kit/controller (which I will sell for cheap if someone wants it), a boost controller, an audio system mess of wiring, and a few wires here and there for different things. As far as I can tell there weren't any significant ECU wiring modifications, but would be interested if there are any modifications people typically do that would impact the EGR system. I know on DSMs it is common to replace the EGR-T sensor input on the ECU side with a wideband input for example.

There's a lot of other things I'm forgetting or not including because it's unrelated (like replacing all the brake rotors/pads/caliper seals/lug studs/lug nuts etc), but I don't think any of those things should impact the EGR system. I am not sure if the car has an aftermarket fuel pump, or if the engine has any internal modifications. When I did the timing belt change I'm 99% sure the cam gears were stock, and the previous owner told me he's never opened up the engine, which I believe.

Any help is greatly appreciated. Let me know if there's anything I can clarify to help get answers.

 

If the ECU has been remapped for a 4 Bar or greater MAP sensor. The test routine the ECU uses with the EGR valve will fail. Since the voltage change is different compared to the stock 1 BAR map sensor. There is a stock looking 3 BAR replacement for the 1 BAR but tables have to be changed to use it. I think it can work with EGR. But beyond 3 BAR I don't think it will work without EGR disabled.

It is also possible you have a bad map sensor even an OEM one will trigger EGR code if it doesn't see a drop in the MAP reading when active.

Everything else you did sounds spot on. I had to put clamps on my EGR to stop hoes popping off.

Mitsuatb

 

Make sure you have the OEM 1 bar MAP sensor.

Measure vacuum. The 272's may not make enough vacuum for the EGR to function properly.

 

Thanks for responding guys. The map sensor that was on the car was the original map sensor (as far as I can tell), and I've since replaced it with an OEM map sensor, MN153281. So I don't believe it is the map sensor, although I could try the original one again to see if there is a difference. Also as I mentioned I did flash the ecu back to stock. I believe I flashed a stock 88590015 rom onto the ECU but I'll double check this this week. Both of you however are really getting at the crux of my question. What does the ECU do to determine that a P0401 condition has been met? Based on your posts I'm inferring that it is indeed looking at the signal from the MAP sensor for a certain change in condition. This would make sense as I wasn't able to set the EGR code or trigger a P0401 code until I replaced the idle speed controller. For anyone interested, I believe my old idle speed controller was stuck closed, so my BISS had to be fairly open. Once I replaced the idle speed controller and properly adjusted the BISS, the P0401 DTC started showing up almost immediately any time I go to drive the vehicle. It sounds like perhaps I will need to locate a set of stock MIVEC cams to cure this issue...

 

Thanks for the info.

 

I double checked and I did indeed use a 88590015 rom. I'm going to go ahead and log some driving with the car and specifically look at the map sensor values reported and how they change when going through the drive cycle for EGR. If anyone has a log they could post of them driving their car with fully functioning and enabled EGR on stock cams in an evo 9 (MIVEC) that would be super awesome as that would tell me what's going wrong. I'm wondering if it's possible for me to fix this by slightly boring out the hole in the intake manifold that restricts flow to the map sensor, although I'd want to be fairly certain of that before I go through with it obviously.

 

Alright, I finally was able to find time to log some data with my car. Here is a clipped log of driving following the service manual's recommendation for EGR drive cycle (hold 37 mph for 20 seconds in 4th gear then coast to idle). I'm not sure what this is supposed to look like, but looking at EGR duty cycle, I'm a little surprised by what I'm seeing. I checked with an OBD scanner prior to this drive and the CEL was pending but not illuminated. The first time I followed the drive cycle the CEL immediately came on. In the section of the log below it looks like EGR duty cycle is non-zero while I'm holding 37 mph then drops to zero when I lift before momentarily jumping to 100 and back to zero then slowly climbs. I'm guessing this may be some sort of internal test it is conducting to try and force a stuck solenoid to open or something, but I don't think this is typical operation in a working system. I also logged the "MAP scaled" channel but it appears to be set up incorrectly and produced garbage data. I'll need to look more into how I can log the factory MAP sensor's raw data.

 

I had a look at what sets the P0401 DTC in the FSM, and its a check the ECU does by monitoring the MAP pressure before and after it opens the EGR valve. It is expecting to see the intake pressure increase by a certain amount after the EGR opens. If it does not detect that increase while testing, then it will set the code.

The minimum amount of pressure increase it is expecting to detect is 0.42 psi. Anything lower than 0.42 psi and it will set the code.

There are several causes for the P0401, it would be worth checking these to see if they are contributing to the pressure not increasing:

• EGR valve is stuck. This would definitely cause the pressure difference not to meet the threshold and throw the code.
• EGR control solenoid is faulty. Solenoid is attached to the back of the intake manifold. Would be worth bench testing this solenoid to make sure it still operates. Faulty solenoid might not open the EGR and the ECU wouldn't see the change in pressure. This is less likely in your case since you aren't seeing a P0403, which is another code the ECU will set if it detects the solenoid isn't operating.
• Not enough vacuum to control the valve. This is what the other guys are talking about, 272 cams might not create enough vacuum to actuate the valve. If the valve is sticking or plugged that might create more work for the vacuum to do as well.

I think I would approach troubleshooting this by following basically what the FSM (and LetsGetThisDone) suggest. First thing is to test the vacuum in the intake manifold.

At idle, you should see the MAP sensor read between 54 - 68 kPa (8 - 10psi). This is with stock cams. Yours will read a higher value (less vacuum) but you can compare your idle vacuum with the OEM value.

If the MAP sensor is reading correctly, then the FSM suggests to clean out the EGR valve and EGR passage in the intake manifold, then re-test.

 

You will want to log the MUT Request 38 for the MAP sensor, as that is the value the P0401 will be monitoring. It should be in EvoScan under "Boost (MAP)" with a 38 in the Request column.

 

This is extremely helpful, thanks. I'll log again and look at these values. I picked up a set of stock cams and was thinking I might try swapping just the intake cam to see if that solves the issue. As I mentioned earlier, when I ground the pin at the ECU the idle quality significantly changes, so I know the EGR system is working.

Thanks, I'll need to look into this more. The reason why I was seeing "MAP Scaled" or whatever is because I had evoscan set to "3000GT EFI" (I have a stealth). I tried logging again with "EFI" but didn't see a "boost (map)" channel. My generic OBD II scanner can stream the MAP so I know it's working I just need to figure out evo scan better.

 

Last month i cleaned EGR valve and now its working properly.


 

So, I've cleaned the EGR valve a few times and confirmed it's operational. I just got back from driving the car again. I swapped back to the stock cams and still have this issue. I'm going to try tomorrow to take the EGR valve off again and clean the EGR ports again to see if that does anything. I've done this before, but I could only get 8-12 inches down the port in either direction. On the intake manifold side I'm going to come in from the throttle body side to verify that that entire path is clear with a bore scope, and for the cylinder head side I'll just have to find a more flexible pipe cleaner or something to jam further down in there. This is becoming extremely frustrating as I've now owned this car for over a year and still haven't been able to legally register it. Granted when I bought it it had a LOT of issues that needed sorting first, but still.

 

I experienced the same issues with my 03 for a month. I replaced egr, but kept getting a pending code for P0300(still get this ) and egr would never set. I replaced my hks 272/272 with stock cams which increase vacuum. I then swapped ECU’s and loaded the correct oem rom onto it. EGR set with the new ecu right away. I’m not sure if there’s a correlation with it but I did get lucky enough that the p0300 didn’t come onto that ecu just long enough to set monitors and was able to pass inspection. If you’re able to swap ecu’s to make sure there’s nothing wrong with it, try that.

 

I'm gonna try and smog it tomorrow. I was thinking the most likely cause of the problem is that the EGR port is clogged, and it does seem like every time I've made a change it took longer for the pending code to show. I decided to drive it again tonight and see if the pending code became a full on CEL since in the past it has taken two drive cycles for a pending code to become a CEL. I also decided if it is carbon build up causing the EGR passageway to be clogged, the best way to unclog it might be to get the exhaust gas really hot, and then max out the EGR flow. So I floored it a bunch and then immediately let the vehicle coast down. After doing that I turned the vehicle off for a few minutes, turned it back on, and the pending code went away and the monitors are all set. So it is possible the code was carried over since when I had the aftermarket cams, and it needed to see two cycles to clear, or that the EGR port was clogged and this whole time I've been trying to clear drive cycles it's been clearing up little by little. In any case, hopefully tomorrow I can smog it and finalize the paperwork to get it registered again.

I will say though the kelford 272 cams do feel like they added a significant amount of power down low. I may need to confirm that the cams were the issue and swap back if I do successfully pass smog.

Also also, the stock cam position sensor housings use RTV to seal to the cylinder head. This feels ghetto to me even though it's OEM, so I removed the sensor housings, cleaned all the RTV off the housing as well as the head, and then got o-rings sized for the groove in the factory housings and put it back together. So far they have not leaked. I was able to change out the exhaust one too without draining the coolant, so that is possible. Hopefully this doesn't become something I need to change out every few years, but even if it does that still feels easier than cleaning off and re-doing RTV. I may look into getting custom square o-rings made that fit better if the ones I got don't work out.

 

O.O

passed