1996 Lexus LX 450 EGR code P0401

Tiny
MSHARIEF
  • MEMBER
  • 1996 LEXUS LX 450
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 188,000 MILES
My car engine light came on. It's giving me a code which says egr flow insufficient. I replaced the egr valve and the egr vacuum modulator. Both items replaced is brand new. After erasing the code, two weeks later the engine light came back on and its giving me the same code. Do you know what else might be the problem for this? Even though the engine ligh is one, my car is driving and idling very good. Should I troubleshoot this problem further or since my car is driving good, not to worry about this? By the way You have helped me solved a car shake problem I had. Thanks for that.
Friday, February 27th, 2009 AT 4:22 PM

1 Reply

Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
Hello. Thanks for the donation. Much appreciated

Hope this helps. Let me know.

DTC P0401 - INSUFFICIENT EXHAUST GAS RECIRCULATION (EGR) FLOW DETECTED
CAUTION:If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction.

Circuit Description
The EGR system recirculates exhaust gas through intake system to reduce combustion temperature and NOx emissions. The amount of EGR valve opening is regulated by the EGR vacuum modulator according to engine load. Vacuum source to valve is controlled by the Vacuum Switching Valve (VSV), which is controlled by ECM.
The EGR valve is closed (VSV on) under the following conditions:
Engine is not warmed up.
Vehicle under deceleration.
Light engine load.
Engine racing.
DTC is set when EGR temperature sensor value does not exceed ambient air temperature by more than 104 °F (40 °C) after vehicle is operated for 3 to 5 minutes (50 MPH or more). Possible causes are:
EGR valve stuck closed.
VSV short circuit.
EGR temperature sensor open circuit.
EGR vacuum hose disconnected.
ECM.
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Friday, February 27th, 2009 AT 5:17 PM

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