So after a bunch of searching, I haven't come up with any real solutions.

I've got a P300 (I think) no EGR flow CEL. I do have the EGR port on the intake mani blocked off and no intentions of hooking it back up.

So the question is, how does the stock ECU know there is no flow? I'd really love to make it go away without the hassle of adding a EGR bung to the exhaust mani and building a crossover tube.

--Alex

 

If your stock EGR valve has a potentiometer on the top it measures flow by the amount of vertical movement of the valve.

If you EGR doesn't have the potentiometer, then it uses an analog (0-5v) signal from the Map sensor.

If there is EGR flow, there is less negative pressure or vacuum compared to when there is no EGR flow.

 

EGR is good.

 

^ Well thats some very useful information.

 

I get the P0400 occasionally due to my blocked off EGR as well, though I've passed emissions twice without it I'd like to know if there's an easy-ish way to keep the light from coming on at all, too.

 

EGR isn't something that usually bothers me. But, in this case it would be a PITA to connect. Not really in the mood to fab up all the plumbing for no real change in the system.

I'm going to look into our valve a little more this week. Hopefully I can figure something out.

--Alex

 

Looks like mrtonyg was right. OBDII cars have a MAP sensor. Didn't know that.

There's a switch in the top portion of the valve itself. This is the only indication on the OBDI EGR valves. (they have one vacuum port) This should let the ECU know that the valve is physically open. On the OBDII valves, there are two ports, one for the opening vacuum source like the OBDI valve and another that feeds a fender mounted MAP sensor.

So I need to check a bit more, but I bet we can just run a false signal to the MAP portion when the EGR valve is engaged.

--Alex

 

So what difference if theres flow or not though?

The map should still change and stuff no?

 

Im gunna check my CEL's this weekend and see if i have been getting one for the EGR. (i know i have one for the front and rear o2 sensors and MAF cause they are all disconnected).

I have everything connected, just have the actual pipe removed and blocked off.

 

Alex, the PCM is looking for a change in the MAP signal at part-throttle cruise. If there is no change from the MAP the PCM determines that there is no EGR flow.

Basically, when the EGR opens it introduces exhaust gas into the intake manifold thus increasing the pressure slightly.

 

I guess my assumption was that that sensor read the pressure in the EGR tube. I would have thought to read true MAP they'd connect it to the manifold instead of to the valve and thereby avoid having to make a different valve to accept the sensor port.

I'm going to put a gauge on it tomorrow and see what happens.
--Alex

 

So yea, I put a gauge on the line and it does read MAP. Gunna have to play around a bit more. Can't seem to find a datasheet for the sensor. Its a Mitsu P/N BPS1 18 211 if anyone else can find it.
--Alex

 

left my connected on a 2001 just did not tap the manifold. almost 2 years and no EGR code

 

On my 97, all I did was remove the egr tube. I didn't block off anything or do anything to the vac side of the system. It never threw a code in the 3 years that I ran it like that...

 

Sounds like I have a few things to try....
--Alex