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P0402 code Excessive flow
My 96 Camry XLE V6 has a code P0402. Excessive flow. The dealer wants to replace the EGR, VSV, and something else for $840. FIrst, I don't trust that dealer for several reasons, so I think they want to change it all out to be sure. Should I start with the VSV, and are there more than one? How do I identify the culprit? THe EGR is right on top, so I thought I would just buy one on line. Advice?
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The code is set if the valve is physically lifted more then 0.1 inch when the EGR system is off. The EGR is off (valve closed) when the engine coolant is cold, throttle closed-idling and a few other times.
The EGR valve is moved by a vacuum diaphragm, the vacuum coming from the intake manifold. The VSV controls vacuum On/Off, turning the EGR system on and off. When the VSV is on, the valve can move more open or closed regulating exhaust gas based engine needs (vacuum). The computer knows the physical position of the valve by means of a position sensor mounted on the EGR valve body. The valve is either not seating fully when closed most likely due to carbon build up, the VSV is not closing allowing vacuum to get by or the position sensor has failed and is given the computer incorrect info. Could also be wiring issues but you should be able to these. If you disconnect the vacuum line going to the VSV from the intake manifold the EGR system should be off. If the system is working correctly there should not longer be any EGR gas flow. If the EGR valve was stuck open too far the exhaust gases would cause the engine to idle poorly or if open far enough not start. How does the car idle? If the same as before the check light came on might be the position sensor. The AutoZone website may have diagnostic info on the site vehicle repair guides. The Rockauto website would have the parts listed, often with photos. There is only one VSV for the EGR system but the may be other VSV's mounted on the engine. Make sure you find the correct one. The one with the hoses running from the intake manifold and the EGR valve. |
Originally Posted by toyomoho
(Post 64317)
The code is set if the valve is physically lifted more then 0.1 inch when the EGR system is off. The EGR is off (valve closed) when the engine coolant is cold, throttle closed-idling and a few other times.
The EGR valve is moved by a vacuum diaphragm, the vacuum coming from the intake manifold. The VSV controls vacuum On/Off, turning the EGR system on and off. When the VSV is on, the valve can move more open or closed regulating exhaust gas based engine needs (vacuum). The computer knows the physical position of the valve by means of a position sensor mounted on the EGR valve body. The valve is either not seating fully when closed most likely due to carbon build up, the VSV is not closing allowing vacuum to get by or the position sensor has failed and is given the computer incorrect info. Could also be wiring issues but you should be able to these. If you disconnect the vacuum line going to the VSV from the intake manifold the EGR system should be off. If the system is working correctly there should not longer be any EGR gas flow. If the EGR valve was stuck open too far the exhaust gases would cause the engine to idle poorly or if open far enough not start. How does the car idle? If the same as before the check light came on might be the position sensor. The AutoZone website may have diagnostic info on the site vehicle repair guides. The Rockauto website would have the parts listed, often with photos. There is only one VSV for the EGR system but the may be other VSV's mounted on the engine. Make sure you find the correct one. The one with the hoses running from the intake manifold and the EGR valve. |
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