2001 Toyota Camry code p401

Tiny
PAC2
  • MEMBER
  • 2001 TOYOTA CAMRY
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 128,622 MILES
We have replaced all the EGR related components. EGR valve, egr modulator, vcv valve, we have replaced the MAP sensor, cleaned all vacume ports in the TB and the EGR tube to the manifold, and still get code P401 after 10 to 25 miles in town driving. Any ideas!

Brad
Personal Automotive Company
25.-759-5686
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Tuesday, May 5th, 2009 AT 6:43 PM

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Tiny
RASMATAZ
  • MEMBER
The egr system is composed of an egr valve the opens vacuum from exhaust to intake manifold, a vacuum modulator that regulates the amount of vacuum introduced to the egr valve and finally the egr vsv (vacuum switching valve) solenoid that directs vacuum flow to the egr valve after a command from the ecm. A quick way to test this is to manually pump 3-4 inches of vacuum to the egr valve during idle and the engine should stall. This shows the egr valve is working. The modulator itself is nothing but a regulator valve that that reduces the engine vacuum from 18-19 inches to 3-4 inches needed by the egr valve. This modulator pressure can be checked by teeing a fitting and measured by a vacuum gage.

Finally, the vsv solenoid can be tested with an ohmmeter to check the resistance of the windings. However, it is reported that this part has a high attrition rate because of it's exposure to heat causing intermittent movement of the shaft inside. This is the part that should be checked thoroughly and replaced if possible.
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Tuesday, May 5th, 2009 AT 10:39 PM
Tiny
PAC2
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Ok! In checking the operation of the VSV I have confirmed the valve is opening consistently after cold start. I have checked voltage and ground conditions and all is operating per manufacture specifications. I have confirmed the VSV working on the bench and working smoothly. I also installed a new one as well and compared values of the new to the original. I have applied 3-4 inches of vacuum to the EGR valve at idle and the engine stalled. We have another customer with the same make, year, and model with the exact same symptoms. Have you had any other inquires of this type in the past? I am wondering if the O2 sensors don't see adequate change in oxygen during EGR request from the ECM if that could generate this code. I do not see this in the operational description or code setting criteria in Mitchell's. I have cleaned the TB in and out and checked idle vacuum as well as ported vacuum all with in specs. I am open to any idea at this point.

Thank you for all your input!

Brad
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Wednesday, May 6th, 2009 AT 2:32 AM
Tiny
RASMATAZ
  • MEMBER
Recheck the EGR modulator and MAP sensor


http://www.2carpros.com/forum/automotive_pictures/12900_EGR_modulator_1.jpg

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Wednesday, May 6th, 2009 AT 6:53 AM

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