Excessive EGR Flow Detected, Code 16786 P0402
- Thread starter gsbar
- Start date
Mr Wizard
Veteran Member
Had the same code on mine. Reason was because the EGR valve was so jammed full of crap that it couldn't close. Remove the EGR and just clean it out. Code went away immediately for me.
yatzee
Top Post Dawg
i had that code come up from time to time in the 02 Golf. EGR was fine - just erased it and went on with my life. It usually threw when pushing a long at a high gear at low speed.
P0402 16786, Excessive EGR Flow Dtected
Fellows, I removed EGR and it was plugged. I cleaned the EGR valve and exhaust pipe tube from EGR to exhaust manifold. EGR is free now and checked with vacuum pump and stays open when vacuum applied. Put everything together, clear the code withy my Vag-Com. After 100 kms of driving the chaeck engine light came on with the same code. Any other suggestions or fix to this annoying problem???
Fellows, I removed EGR and it was plugged. I cleaned the EGR valve and exhaust pipe tube from EGR to exhaust manifold. EGR is free now and checked with vacuum pump and stays open when vacuum applied. Put everything together, clear the code withy my Vag-Com. After 100 kms of driving the chaeck engine light came on with the same code. Any other suggestions or fix to this annoying problem???
NarfBLAST
Top Post Dawg
I came up with this "maf twist" fix:
EGR del and CEL, new quick fix - TDIClub Forums
But before you wade thru that thread, can you tell us what your MAF Specified and MAF actual are reading at idle using VAG-COM? Also it would be worth wile to test your MAF using vag-com following the procedure in the TDI FAQ if possible.
EGR del and CEL, new quick fix - TDIClub Forums
But before you wade thru that thread, can you tell us what your MAF Specified and MAF actual are reading at idle using VAG-COM? Also it would be worth wile to test your MAF using vag-com following the procedure in the TDI FAQ if possible.
bluesmoker
Veteran Member
Fellows, I removed EGR and it was plugged. I cleaned the EGR valve and exhaust pipe tube from EGR to exhaust manifold. EGR is free now and checked with vacuum pump and stays open when vacuum applied. Put everything together, clear the code withy my Vag-Com. After 100 kms of driving the chaeck engine light came on with the same code. Any other suggestions or fix to this annoying problem???
try turning off the egr with your vag com
http://www.tdiclub.com/TDIFAQ/TDiFAQ-7.html#j
turbocharged798
Veteran Member
That is not recommended any more as some people have found that it causes the ECU to retard timing.
NarfBLAST
Top Post Dawg
Either your EGR valve is not opening (likely) or your MAF is reading too high (unlikely). You said it opened when you applied vacuum, so next thing to check is if the vacuum line that goes to it has vacuum at idle it should be sucking pretty good.
Also, you could apply vacuum to the egr valve manually at idle and watch the MAF actual numbers come down to the specified values. That would confirm if the EGR valve and the MAF are both working well together. When the EGR valve opens, the exhaust gasses take the place of fresh air that would come thru the airbox and be measure by the MAF.
TmpaFL2000Dsl
Veteran Member
tomfoolbee1
New member
- Joined
- Jul 4, 2009
- Location
- wake forest north carolina usa
- TDI
- 99.5 Jetta tdi Red; 99.5 Bora tdi Green 01 jetta tdi
Get a diesel geek race pipe and throw the egr assembly in the waste basket! Its just gonna clog your intake up (if it hasn't started to already). Buy a spare ecm from salvage yard and send it to a tuner to have egr function deleted. Then swap ecm's when it comes back in the mail.
01jettatdibreezy
New member
it wont let me view the thread, it says im not of privilege aha but my cars reading egr code and im in the process of checking if there is any vaccum, or if it is the harness so if anyone has any pointers or help its muchly appreciated
jkaiser
Veteran Member
I am having the exact same problem, keep us posted and I will do the same. Based on my reading EGR is not opening properly.
NarfBLAST
Top Post Dawg
Yep, emissions device defeating topics are banned from this site, so, I have posted a couple of videos on YouTube with explainations on how to do the MAF twist and how the EGR system works... will add these links to my signature too... These videos are for interest purposes only and not to be discussed here (or this thread would be deleted too):
VW TDI ALH EGR System Explained
How to do the VW ALH TDI MAF twist
Area351
Veteran Member
I just had ash 02 Jetta in the shop early this week with the same code.
Cleaned the egr thoroughly and it came right back. After quite a bit of scanning and wondering what was going on and VCDS reading way more actual MAF than requested, it turned out that those numbers were correct.
The N18 solenoid took a dump and was stuck open letting exhaust gas in all the time. After replacing the N18 solenoid, the actual and requested MAF settings were nearly identical and the problem went away.
With the bad N18, the EGR valve was at ~ 80% duty cycle. After the N18 was changed it went down to ~40%.
In case you're wondering, it's the solenoid with the black top on it right next to the N75 solenoid with the white top. They are both mounted on the firewall, just left of the brake booster.
A quick test with 12V applied to the solenoid confirmed that there was no audible click and that it was stuck.
Cleaned the egr thoroughly and it came right back. After quite a bit of scanning and wondering what was going on and VCDS reading way more actual MAF than requested, it turned out that those numbers were correct.
The N18 solenoid took a dump and was stuck open letting exhaust gas in all the time. After replacing the N18 solenoid, the actual and requested MAF settings were nearly identical and the problem went away.
With the bad N18, the EGR valve was at ~ 80% duty cycle. After the N18 was changed it went down to ~40%.
In case you're wondering, it's the solenoid with the black top on it right next to the N75 solenoid with the white top. They are both mounted on the firewall, just left of the brake booster.
A quick test with 12V applied to the solenoid confirmed that there was no audible click and that it was stuck.
Last edited:
RRRon
Member
- Joined
- May 13, 2013
- Location
- Phoenicia, NY
- TDI
- 99 New Beetle 02 Golf and putting a ALH in a 03 Gasser Jetta Wagon
My vacuum pump was very leaky. That might have caused the P0402 too. Changed the pump, and it is gone for now.
Matt-98AHU
Loose Nut Behind the Wheel Vendor
More vacuum = more EGR rate!
With VCDS, you can run basic setting 03, note the MAF values EGR on vs. off. With it on, you should see somewhere less than 250 mg/st typically. With it off, 400+ mg/st.
I have had N18s stick before as well. One in particular likely happened because the EGR diaphragm had weakened and the computer increased the N18 duty cycle to compensate and it set EGR low flow code. Replaced EGR and all of the sudden the car could barely idle and wouldn't go above 1500 RPM. It ran better with the old EGR! Put the mityvac to the VAC OUT nipple on the N18, sure enough, even when running basic setting 3, the N18 is just sending 100% vacuum full time to the EGR.
With VCDS, you can run basic setting 03, note the MAF values EGR on vs. off. With it on, you should see somewhere less than 250 mg/st typically. With it off, 400+ mg/st.
I have had N18s stick before as well. One in particular likely happened because the EGR diaphragm had weakened and the computer increased the N18 duty cycle to compensate and it set EGR low flow code. Replaced EGR and all of the sudden the car could barely idle and wouldn't go above 1500 RPM. It ran better with the old EGR! Put the mityvac to the VAC OUT nipple on the N18, sure enough, even when running basic setting 3, the N18 is just sending 100% vacuum full time to the EGR.