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VW Tech 1
VW Tech 1, VW Technician
Category: VW
Satisfied Customers: 412
Experience:  ASE Master Tech, Master VW Factory Tech
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Volkswagen Beetle TDI Why do I get a P0402 error code, Excessive

Customer Question

Why do I get a P0402 error code, 'Excessive EGR Flow', when I have BLOCKED the pipe between the EGR valve and the exhaust manfold? I have an idea, which is NOT a good one, but I would like input from the pros. Also, when I erase the error code(s), why will they not reappear until I have turned off the ignition, and turned it back on again? I have been under the impression (maybe mistaken) that the onboard computer monitored all these functions CONTINUOUSLY. Am I wrong again?
Submitted: 6 years ago.
Category: VW
Expert:  VW Tech 1 replied 6 years ago.

Thanks for using Just Answer.


That is a really good question. I wondered that also the first time I say this fault with a egr cooler that was plugged. Long story short - the computer in those years knows there is fault but doesn't actually know high from low. There are other instances of this on this year cars with boost pressure upper limit exceeded and the turbo will be blown up and not boosting at all. The computer is confused. The next part of your question I will answer also - The systems are constantly monitored but some systems require more than 1 or 2 trip cycles to set a fault or a check engine light. Some faults are 1 trip cycle and others are 2 or 3. Trip cycle is defined as a start up and drive to operating temperature and then cooled off again = 1 trip cycle. hope this helps let me know if you need anything else.

Expert:  VW Tech 1 replied 6 years ago.
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