Hello all, I've recently been trying to fix a p1105 engine code on my '99 q45, because I've been getting horrible gas mileage and weird idle. I've determined that it is any vacuum leaks or electrical problems with the MAP sensor or EGR valve. I'm pretty sure it's the EGR solenoid since my EGR valve would move freely when I moved it, but didn't have any vacuum and didn't move when I revved it. I've been using user paranoidjack's post on removing the intake manifold and plenum to get the EGR solenoid, since other threads said it was under the manifold. I found two sensors that look identical as far a I can tell, one of them is under the plenum, which I haven't removed, and the other is accessible with the intake manifold removed. Does anyone know which one of these is the EGR solenoid and how to test it? Any advice on the whole EGR solenoid topic is welcome. Thanks!

This should help.

It kind of looks like both the EGR solenoid valve and the MAP/BARO solenoid are pointing to the same place, are they the same thing?

Nope, they're separate. Just trace the plumbing. One tube on both will come from the manifold gallery,. The other tube on the EGRC solenoid tube will go straight across to the EGRC-BPT valve. The MAP solenoid's second tube will connect to the Abs Pressure sensor.

Ok, thanks. Am I correct in assuming that the EGR solenoid is the problem since the EGR valve isn't functioning at all?

Could be the control pot too. The old Pathies use a vacuum pot to modulate a vacuum pot, that's what the EGRC-BPT valve does. If that's leaky or stuck then the EGR likely won't move even if the vacuum signal from the solenoid is healthy.

Awesome, thanks for the help!

I've done some research and I agree with you, it's either my EGR solenoid orcthe EGRC BPT valve, however, I currently have my intake manifold off, so I can't really test my EGRC BPT, and I believe you're supposed to test it by feeling the diaphragm? but I don't think the diaphragm is open/available to be felt. Do you have any recommendations on how to test the EGRC BPT valve and the EGR solenoid with putting my engine back together? I don't want to put it back together just to test the valve, the find out that the EGR solenoid is actually the problem.

The most likely problem with both is a punctured diaphragm, just put vacuum on the business end and see if they hold it or leak it out.

I know Vstar is already helping you, so I'll try not to distract....but...you originally stated P1105. That references the MAP/Baro. P1400 would be for the EGRC. both solenoids have similar operation, and the fsm has a diagnostic for P1400 that you can use to verify that both solenoids are activating and properly controlling the vacuum direct/bypass. I've not personally had one of these solenoids fail on a nissan, but on my daughter's honda K24A1, there is a vacuum controlled IMRC (variable intake) solenoid, which failed, so I imagine it's possible on a nissan.
If your solenoids checkout (bench test), then I'd go down the BPT (back pressure transducer) path that Vstar suggested. The BPT is quite sensitive, takes less than 1 psi to move the diaphragm as I recall.
One other thought: might only apply to the vapor control, and NOT the EGR, but are you certain that you DON'T have to be in gear and above 4mph (rear wheels off the ground) to allow the EGR control to activate?
Also, since you have the upper plenum off, pull the EGR tube (aka the piccolo) out of the plenum and clean that b!otch good....

I watched some videos on testing solenoids, but it seems that I would need to turn my car on to do so which I'm assuming isn't wise with so many wires and hoses disconnected. Is there another way to test? I'm planning on testing current and vacuum on the EVAP canister, EGR solenoid and MAP/BARO solenoid if I can get to them, I haven't removed the lower plenum yet so I'm not sure what either look like though.
I'm also kind of confused about the p1105 but in my limited knowledge and research, all I can find is that it's the EGR solenoid, whenever I look up info about the MAP/BARO it just gives me results about the MAP sensor, not solenoid, which I've already replaced and has adequate voltage. I suppose I'm just getting a lot of the sensors and solenoids confused.
I've only tested the EGR valve by feeling the diaphragm and giving it a few quick revs, as I've seen suggested online, so I don't know if the wheels need to be moving, but as far as I can tell it's getting no vacuum, thanks for chiming in by the way, I'll take all the help I can get.

get a 12v power supply like a simple transformer (old laptop, maybe) so you don't have to run the car to check (or I suppose you could use leads from your engine battery), just remember it can be dangerous to instantaneously supply 3000-5000A if leads short.
with the solenoid harnesses disconnected, you want to energise the solenoids and hear the click, verify vacuum porting changes. then, just as important, the solenoid releases (they can get sticky) when you remove the 12v, and the vacuum porting changes back.
I find the easiest way to test the EGR in situ is to hold the revs steady at ~1500 with engine warm (again....*possibly* in gear with drive wheels off floor), and feel the EGR diaphragm pulse. remember though, that even if the EGR valve is working, that piccolo tube I mentioned above gets plugged up and then eventually the EGR valve itself gets plugged.

I try to make a point of not interfering when someone else is already helping...just take my thoughts in this thread as general info from a semi-retired engineer.....

3Q Jay wrote: ↑

Mon Mar 29, 2021 2:57 pm

I try to make a point of not interfering when someone else is already helping...just take my thoughts in this thread as general info from a semi-retired engineer.....

C'mon, Jay, I'm not one of those pinheads who gets offended when someone else knows about a subject. In this case, you probably have more specific and useful knowledge about oldies than I do. Same for Md, I defer to him all the time. Nowadays I see stuff older than 15 years once in a blue moon, and it's sadly true that you tend to lose what you use rarely.

For the OP, all of that is very good advice. The only thing I'd add (for everybody) is that putting test voltage on stuff is another good use for the short-circuit tool I described in "The Problem With Shorts Part II". With that in the circuit, there's no risk of crossing jumpers and frying anything with cold-crank current. The worst that happens is the bulb lights up for a blue light special in the "duh" department.

When I bought my Q a few years ago it had the P1105 code as well. Turns out the sensor itself was fine BUT some critters chewed through one of the vacuum lines. I also had one knock sensor code so I ended up replacing those. I will say if you do this yourself make note of where the vacuum lines are routed. The diagram above is VERY helpful but its still hard to see. Good luck