EGR Delete on AHU (poor man's version)

mr.mindless

Veteran Member
Joined
Jan 23, 2006
Location
Rochester, NY
TDI
2002 Galactic Blue Jetta GLS
On a test drive now, think the issue may be licked. I had a typo in my EGR adaptation, I was set to 32768 instead of 33768.

Now at 33768 if I recall right my MAF target is 350 or maybe 370 (computer is shut down now but I do have some logs saved if needed). I am not hitting that but perhaps I'm getting close enough now to be within the window. The only times I'm seeing EGR duty at less than 84% is on hard acceleration, but I'm at 4-5x the driving distance and key cycle count as where I was getting a CEL before.

Fingers crossed!


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thechoochlyman

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May 7, 2015
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Campbellsville, Kentucky
TDI
97 Passat
I adjusted my adaptation number as well - I never thought that it might interfere. Perhaps I should set that back to normal and see what happens.

Just a couple pics of what I've got done so far: Blue wire has the 1k resistor spliced into it, under the red heat shrink tubing.


What I had going on with the relay. Male spade connectors for attaching directly to the N18 harness.
 

thechoochlyman

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May 7, 2015
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Campbellsville, Kentucky
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97 Passat
Ok, this may be a bit over the top, BUT I think it will help me out.

My HVAC recirculation solenoid has been out of commission for quite a while - the rubber diaphragm under the dash cracked, so I replaced it with a pull cable. Since that vacuum solenoid is no longer needed I spliced some extra wiring to the push button's harness. Now I can actively engage and disengage the resistor while I monitor VCDS from the driver's seat. And once I'm done I'll have a handy way to engage any accessories I'll want to add later.

 

thechoochlyman

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Campbellsville, Kentucky
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97 Passat
So, as it turns out my resistor does work!

Right now my adaptation value in channel 03 is 33768, and my target MAF reading is 350.0 mg/str at a 4.8% duty cycle. Decreasing that value back to 32768 reduces my targeted MAF reading to 250. Since I'm not reading nearly that low at the moment, I figure I might as well leave that number as it is.

Unaltered, my MAF reading is around 469 mg/str. Applying the 1k resistor brings that number down to 389-392. I would assume it's so high not just from disabling the EGR, but also because I bypassed the blowby tube leading to the turbo inlet.

Since I'm now using a 5-pin relay, I'm thinking I can use two different resistor values. The 87A terminal will always be connected to the ground, and the 87 terminal will connect when the relay is engaged. I'll put about a 1500 ohm resistance on the 87a pin for when the EGR system is supposed to be off. I'll then put around 1700 ohms on the 87 terminal when the EGR is "activated." It will see a slight difference, and think that everything is working.

Of course, I'm still not sure how the vacuum solenoid is supposed to engage and disengage itself. If it doesn't receive a steady current of electricity when the computer engages the EGR system, then this type of magnetic coil relay won't work by itself here.
 
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thechoochlyman

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Joined
May 7, 2015
Location
Campbellsville, Kentucky
TDI
97 Passat
I recently dug my SSR out of the trashcan and tested it again with a 9V battery. It does work. I went with the Bosch relay because I hooked the SSR up to the N18 harness and it didn't do anything. However, with the 1k resistor on there it's giving me about 1800 ohms for some reason. I already soldered the resistor to the SSR, so I'm not disconnecting it now. But it appears that I must redo my configuration once again.

EDIT: I'm gonna have to do the Bosch relay after all. By using the SSR I'll essentially have to run two resistors in parallel, and if I'm correct the signal will always just take the path of less resistance. I'll have to using the 87A pin with 1600 ohms and the 87 pin with 2600 ohms.

I'm learning so much about electronics here. haha
 
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thechoochlyman

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May 7, 2015
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Campbellsville, Kentucky
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97 Passat
Well I found out a few things over the weekend.

The MAF sensor works in reverse of what I thought - when the sensor wire and ground are shorted, it reads max airflow. It takes LESS resistance to show less airflow, not more resistance.

I used two values for my resistors - 245 ohms constant, and 188 ohms when the EGR is enabled. The 245 ohms brought my mg/str down to 320, while the 188 ohms brought it to 260. To get 245 ohms I used four 1,000 ohm 1/4 watt resistors, and I obtained 320 ohms with 2 each of 470 and 1000 ohm resistors.

The check engine still didn't go away after hooking this up and watching the mg/str value go down to within normal range. I am still getting two EGR codes, one of which seems to indicate that the N108 itself is bad. Will I have to replace the N108 solenoid even though it's not actually going to be used, or can I hook up some sort of fooling device to that as well?
 

mr.mindless

Veteran Member
Joined
Jan 23, 2006
Location
Rochester, NY
TDI
2002 Galactic Blue Jetta GLS
on my 98, I unplugged the n18 and used its leads to go to the relay. only on/off with a 1k resistor. Mg/ str is well off from requested but it is keeping my light off.

Check for any shorts or opens in your wiring or the car side wiring.


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jnxtheband

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Jun 3, 2006
Location
pdx
TDI
92 GTI AHU swap (gone), 91 GTI VR6
Hey guys, just so you know. VW actually makes an OEM vaccuum switch. Part number: 171919825b Its used on MK2 gas cars with CIS injection from 85-87 for the upshift light in the cluster. From this picture it looks like thye are adjustable as well.

 

Bora-chiara

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Jun 7, 2007
Location
San Tan Valley, Arizona
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ALH, BHW, CKRA
I'm doing this. I am going to get a tune but I have a few things I need to do first so in the meantime I'll attempt this. My SSR is on its way but I have plenty of mechanical relays around if needed. I have a mk4 so I'll probably encounter differences but I'm familiar with wiring and resistors so we will see. If it works I'll solder it all on a little board and wrap it to stow away somewhere. I appreciate you guys and the efforts you've made so far!
 

Bora-chiara

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Jun 7, 2007
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San Tan Valley, Arizona
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Alright I got mine in. IT WORKS! so we've expanded the realm of possibilities to MK4 as well. I wired a Bosch relay and harness I got at a junkyard from another project and followed the previously given wiring instructions. I had an old VW connecter also from the junk yard with the male pins the same size as the plug for the EGR vacuum controller. I pulled the pins out and just soldered them on the the existing relay harness so they can just plug in with no vehicle end splicing.



Then I took apart the MAF connecter. I don't like splicing if I can get away with it so I crimped the new wires into the existing pin on the MAF.



This is my beta test so I will eventually have the wire run through the rubber seal and into the existing loom for another project as I will eventually replace the mechanical relay with a SSR but not like the one above. I'll try to come back and post in this thread the results when THAT project is done.
 

jeffmon

Active member
Joined
Mar 14, 2010
Location
Missouri
TDI
98 Jetta
Almost three years down the road, and I still haven't had any reason to try the SSR. My vacuum switch method still works, and I'm at 525,000 miles now. The reason I checked this thread is that one of my wires pulled out of a connector and I had to check where I had put it. I guess I did a crappy job of tidying up the job. Anyway, this concludes my zombie post.
 

nesdon

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Dec 14, 2007
Location
LA
TDI
2013 JSW, 2009 & 1998 Jetta Sedans
This is a pretty dead thread, but also on point to my current issue. However, I have not been seeing an EGR DTC, only it failing to clear the readiness monitor for the purpose of passing CA smog test. But I would guess the ECU is using the same MAF:EGR signal to clear the monitor.
 

turbodieseldyke

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Jun 6, 2010
Location
Free Mustache Rides
TDI
98 jetta
This should work

A year later, and still no 1403.
I haven't tried it, but if you want to try the solid state relay get one like this:
http://www.amazon.com/Input-3-32V-Output-HHG1D-0-032F-20/dp/B008MU2A8A
A bargain at $3.75. Hook it up like this:

Make sure you "tee" the resistor and relay into the wires on the MAF connector. Don't disconnect them, just remove some insulation from the wires and connect the resistor and relay terminals across the wires. It doesn't matter if the resistor goes on pin 1 of the relay or on pin 2, you just need the two components in series.
Polarity matters. If you use a different solid state relay, make sure the wires that go to the plus terminals are right. If you use an electromechanical relay, the output polarity won't matter, but sometimes there's a diode on the input (coil) which would make input polarity matter. I'm still not sure if the electromechanical relay would switch fast enough.
Please post a reply if you try it and it works.
Jeffmon kindly looked around and found the drawing that's missing from post #15.
 
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