Re: Replaced egr valve and egr sensor and still have code...
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Here is an overview for the code as it relates to Toyota cars.
I would go back and make sure the tubes and pipes are clear.
In most cases, the passage is plugged up, or the sensor does not "see" the flow.
Possible causes
- EGR passage clogged
- Faulty EGR Vacuum Modulator Valve
- Faulty EGR Valve
- Faulty EGR solenoid valve
- EGR solenoid valve harness is open or shorted
- EGR solenoid valve circuit poor electrical connection
- Dead (Weak) battery
- Faulty EGR temperature sensor and circuit
- Exhaust gas leaks
oh yes i know its you EGR valve (Exhaust Gas Recalculation)
A code P0401 most
likely means one or more of the following has happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and
needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the
EGR valve only to have the OBD code return. The EGR valve is not always
the culprit.
Use a vacuum pump and pull the EGR valve open while monitoring
engine RPM's & DPFE voltage. There should be a noticable difference
in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to
a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve
Related EGR Articles: P0400 - P0402 - P0403 - EGR System Explained
Code 401 is for low EGR air flow. The EGR valve allows exhaust gas to be recirculated back thru the intake and reburned. The problem could be the EGR valve, the sensor, or a blocked line.
Normally a shop would use a scanner to watch the operation of the EGR valve and sensor. Code 401 means the sensor is telling the computer the flow is not enough. So the problem could be the sensor rather than the EGR valve. And yes one of the ports could be blocked too.
It basically indicates a problem with the EGR valve or the DPFE sensor. Usually, this is caused by blocked passages in the EGR system, not with the EGR valve or DPFE sensor themselves. To clean them, you will have to remove the throttle body.
Code 401 is for EGR flow insufficient. There is a sensor that measures how much exhaust gas goes thru the EGR valve. The sensor could have failed, or the EGR valve may not be working. The sensor and valve would need to be tested.
Engine size? year? This code is for insufficient egr, usually caused by clogged egr passeges or a bad DPFE sensor. Open egr valve, if the engine idles real rough or stalls, replace the DPFE sensor. If the idle does not change, then take the egr valve off and clean the passages. You cant just keep changing parts hoping you get lucky and change the correct one.
A code P0401 most likely means one or more of the following has happened:
•The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
•There is a blockage in the EGR (tube), most likely carbon buildup
•The EGR valve is faulty
•The EGR valve may not be opening due to a lack of vacuum
In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
•Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticeable difference in RPM's with the EGR open
•Clean out the EGR valve and/or tubing to remove deposits
•Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
•Replace the DPFE sensor (with a good quality / OEM one)
•Replace the EGR valve
make sure egr passage way from valve to intake not clogged and make sure exhaust to egr supply is present and make sure if valve is vacuum operated that senser is ok and vacuum supply correct if electial egr senser then intake probably clogged sense code 401 is insuffence egr flow
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