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Ron Z.
Ron Z., - Toyota Tech -
Category: Toyota
Satisfied Customers: 17788
Experience:  18+yrs experience. State Inspector and Toyota Diagnostics
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99 Camry: cyl..Check engine light is on and says..EGR

Resolved Question:

I have a '99 Camry 4 cyl. Check engine light is on and scanner pulls a P0401 code. Toyota dealer says this means the EGR is bad. I go online and find a simple test that can be performed to determine whether the EGR is bad by pulling the vacuum line leading to it and then depressing the EGR diaphragm up into its housing and then, at the same time, coviering the nipple where the vacuum hose fits with a finger. If the diaphragm does not drop down until the finger is removed, it indictaes that it is good and that the EGR is good. My car passes this test. A little further digging on the net shows the car also has an EGR positioning sensor and some kind of temperature sensor. My question is, could anything else besides the EGR valve itself be malfunctioning that would trigger the P0401 code to come on?
Submitted: 5 years ago.
Category: Toyota
Expert:  Ron Z. replied 5 years ago.

Actually, in my experience, the most common fault item associated with the P0401 is a faulty VSV for EGR. Double check all the vacuum lines to/from this VSV are good. If the visual check is good, suspect a faulty VSV for EGR. It's located on the side of the engine closest to the firewall, about mid-way down. Best access is through the passenger's side wheel well.


Customer: replied 5 years ago.
It all souds good. What does VSV stand for?
Expert:  Ron Z. replied 5 years ago.
VACUUM SOLENOID VALVE - This is the valve that creates the vacuum used to control the EGR. Usually what happens, due to it's location (just under the exhaust manifold), the little motor inside heats up and burns out. Very common.
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