P0401 - EGR System Insufficient Flow - My Turbo Diesel

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koabi I think I've diagnosed this correctly, but I'd love for confirmation. P0401 - EGR System insufficient flow -Tested vacuum to the N18 valve. ~22in/hg -Had someone operate the throttle while I observed the EGR valve - actuator did not move, no matter what was done with the throttle -Tested vacuum to the line that connects to the EGR actuator. No vacuum, no matter what I did with the throttle. Vagcom would show changes with the EGR duty cycle, though. -Used mitivac on EGR actuator. Valve opened with ~12in/hg vacuum and held -MAF is reading higher than expected values. This should be due to more fresh air being sucked in due to no EGR. I had trouble getting EGR duty cycle low enough to see if it did match expected values in that scenario to rule out a MAF issue Conclusion: Replace N18 valve #1 · Feb 2, 2014 I think I've diagnosed this correctly, but I'd love for confirmation. P0401 - EGR System insufficient flow -Tested vacuum to the N18 valve. ~22in/hg -Had someone operate the throttle while I observed the EGR valve - actuator did not move, no matter what was done with the throttle -Tested vacuum to the line that connects to the EGR actuator. No vacuum, no matter what I did with the throttle. Vagcom would show changes with the EGR duty cycle, though. -Used mitivac on EGR actuator. Valve opened with ~12in/hg vacuum and held -MAF is reading higher than expected values. This should be due to more fresh air being sucked in due to no EGR. I had trouble getting EGR duty cycle low enough to see if it did match expected values in that scenario to rule out a MAF issue Conclusion: Replace N18 valve Sort by Oldest first Oldest first Newest first Most reactions #2 · Feb 2, 2014 How did you watch the actuator move (or not move in your case)? Some people mistake the ASV for the EGR, but if you tested the thick vac line going from N18 to EGR and there was no suction then you're probably right. #3 · Feb 2, 2014 (Edited) http://www.partsplaceinc.com/uploads/images/products/large/21327f.jpg tested off black thing to the left not silver thing on the top. I got it right? I watched the arm move, i didn't pull off the intake elbow to observe the valve itself, which probably would have been a good idea. edit: I think you're right and I might have tested the wrong valve. Diagnosis is probably the same, though #4 · Feb 2, 2014 VAG Error Code: 16785 EOBD II Error Code: P0401 Fault Location: Exhaust Gas Recirculation (EGR) System - Insufficient Flow Detected Possible Cause: Malfunction Indicator Lamp (MIL)(K83) active. Reduced Exhaust Gas Recirculation (EGR). Reduced Power Output/Engine running rough. Increased Emissions. Possible engine hesitation. Hose leak/blockage. Basic setting not carried out. Exhaust Gas Recirculation (EGR) Flow restricted/clogged. Exhaust Gas Recirculation (EGR) Valve stuck closed/leaking/faulty. Wiring/Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve faulty. Exhaust Gas Recirculation (EGR) System faulty. Dead (Weak) battery. Exhaust gas leaks. Possible Solutions: Check/Replace Wiring/Connector(s). Check/Clean Exhaust Gas Recirculation (EGR) System. Read Measuring Value Blocks (MVB). Check/Replace Exhaust Gas Recirculation (EGR) Valve. Control deviation < limit from map f (engine speed, desired airflow). Tech Notes: Exhaust Gas Recirculation (EGR) flow malfunction could be caused by a clogged Exhaust Gas Recirculation (EGR) valve or Exhaust Gas Recirculation (EGR) tube. Before replacing any parts try cleaning the Exhaust Gas Recirculation (EGR) valve, tube and passages. When is the code detected?: Low Exhaust Gas Recirculation (EGR) flow control is detected. As taken from my Free EOBD II Error Codes software #5 · Feb 2, 2014 The black thing to the left is the ASV (anti-shudder valve). The EGR is the one on top. You can hear the engine's sound change when it activates/releases, but you have to be listening pretty closely. In order to see it move, you have to remove the rubber air intake hose. The ASV assists in shutting the engine down. It briefly closes when the key is turned off. The good thing is, if this is on your '03 ALH engine, you can remove the EGR/ASV assembly and clean it. #6 · Feb 2, 2014 ok thanks to spah and MT Golf for pointing out that I might be testing the wrong thing. I was testing the ASV which at least seems to work properly. The EGR will not hold vacuum, so it seems like the EGR actuator is dead. Anything that I can do in this scenario besides replacement? I'm not looking at deletion as an option. I'll confirm functionality of the N18 valve by using the EGR vacuum line this time since if I don't I'll find that's dead too #7 · Feb 2, 2014 Sounds like you're on the right track. Does he EGR valve stem itself move at all? If not, it could be so carboned-up it won't move by vacuum, but if you move it up/down a few times with the help of needle-nose pliers, maybe then it will work under vacuum. If not, you're in to a new EGR/ASV assembly, about $170. Testing whatever actuates the EGR vacuum would also be a good idea. The EGR/ASV can be cleaned, but keep the rubber & plastic parts out of the cleaning solution. Insert Quotes Post Reply

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