CEL code P0401?

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Odd thing this morning. After starting the car and driving out the driveway somewhere in the next mile the CEL came on and so I figured "great, the GP fault is back" and began the scan/clear process with the Scan Gauge on the way out to the main hiway. Instead of the P0380 or whatever the pesky GP code was this spring this was a different one, P0401, if I recall (should have wrote it down). Can someone tell me what this generic code may be? No noticeable change in engine preformance/operation.
Here is the real odd part of the deal. After I cleared the code, which didn't come back the rest of the drive, the SG mpg numbers (instant and average) were almost double the "normal" for the 50 mile drive.
Any ideas?? Speed calibration on the SG hadn't changed and the gallons/tank were looking correct for the miles driven up to that point. (12.2 for 631) While it looked impressive, I know that its not possible to get 80 mpg and over many, many tanks of fuel in three different TDIs they have all been quite consistant on the commute.
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Hi, there's a link in my sig for looking up codes...that should probably help out.

Thanks.
Thanks, puter. Unfortunately I'm an idiot for not stopping and writing it down, because none of those seem to "match" my recall of the code number. Maybe it'll come back when I restart it tonite.:confused:
I will have to remember that handy link. Thanks again.
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
No problem. I like it because most of the results also give you symptoms and probably causes which seem to be pretty accurate in my experience.
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Thanks, puter. Unfortunately I'm an idiot for not stopping and writing it down, because none of those seem to "match" my recall of the code number. Maybe it'll come back when I restart it tonite.:confused:
I will have to remember that handy link. Thanks again.
Well, it did come back on after starting it after work and after about a half mile of driving.
Left it on until I got home and scanned w/VCDS. The complete code was 16785/P0401 EGR system Insufficient Flow-Intermittant
So after looking it up on the chart in puter's sig line here is the code explaination:
16785/P0401/001025 - Exhaust Gas Recirculation (EGR) System: Insufficient Flow Detected

Possible Symptoms

  • Malfunction Indicator Light (MIL) ON
  • Reduced Exhaust Gas Recirculation (EGR)
  • Reduced Power Output/Engine running rough
  • Increased Emissions
Possible Causes

  • Exhaust Gas Recirculation (EGR) Flow restricted/clogged
  • Exhaust Gas Recirculation (EGR) Valve stuck closed/leaking/faulty
  • Wiring and/or Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve faulty
  • Exhaust Gas Recirculation (EGR) System faulty
Possible Solutions

  • Check/Clean Exhaust Gas Recirculation (EGR) System
  • Check/Replace Exhaust Gas Recirculation (EGR) Valve
  • Check Wiring and/or Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve
Looks like I need to pull the EGR valve off and look it over. It was well cleaned when the head was rebuilt/TB replaced about 7K miles ago. Vaccum line looks fine. Should add this is on the '03 Jetta.
The very high mpg numbers on the SG are similar to when I drove it w/MAF disconnected.
Any suggestions are welcome.
 
Last edited:

greengeeker

Vendor
Joined
Feb 8, 2006
Location
Cambridge, MN
TDI
2002 Jetta GLS
Marc, I noticed the same SG behavior when I ran without my N18 (was using it as an n75 :)). Start by running an output test in vcds. AFter that verify that your actuator holds vacuum, your n18 is getting full vacuum, and the n18 breather line is not obstructed/kinked.
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Marc, I noticed the same SG behavior when I ran without my N18 (was using it as an n75 :)). Start by running an output test in vcds. AFter that verify that your actuator holds vacuum, your n18 is getting full vacuum, and the n18 breather line is not obstructed/kinked.
Thanks, Nick. I'll check it out. Seemed like a vacuum type thing was the issue and I checked the lines before leaving work but I need to have a real look at it.
You going to HayDays this weekend??
Marc
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
remove the big hose from the egr. put a vacuum on the unit and observe the shaft inside the flap. it should move over. if not, it could just be dirty
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Unfortunately no. Gotta get caught up on my TDI work.
I have to work 'til noon Sat, but will go down after that and stay for Sun.

More oddness going on. Code didn't return this AM, but did after work this afternoon. Cleared it w/SG and then after fueling up it came back on. On the way home the intake air temps also started reading 20+F higher than ambient, and quite a bit more rather quickly, if I ran some boost. This car has always ran rather low IAT (usually less than 10 degrees F above ambient at steady 60 mph cruise) compared to the other ('01) Jetta, but I did do some surgery on the inner fender behind the IC, so always attributed the lower temps to that. Turbo boost appeared to read normal, but a bit of throttle and IAT would climb fairly steady, not normally.
Took the enginee cover off when I got home. Vac lines all look good from the topside and all electrical connectors appear connected. Only thing I found was the tube/hose from the valve cover breather into the intake tube had come loose from the strange plastic "clip", so reattatched that and will try it out in the morning. I can see that might mess up EGR reading, but why would that change anything with the IAT? Or mpg reading, for that matter??:confused:
Guess I'll find out.:rolleyes:
 
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