EGR CODE P0401,IF I APLLY VACUUM TO THE EGR VAVLE THE ENGINE STALLS.THIS TELLS ME THAT THE EGR VAVLE IS WORKING.SO WHAT NEXT

Hi Joe

Like all solenoid valves, you can clean them with throttle body cleaner and then test the solenoid electronically with a 12 volt supply.

P0401 Exhaust EGR Flow Insufficient

Toyota Nation Forum https://www.toyotanation.com > threads > p0401-exha...
May 1, 2014 - The sensor is how the ECM determines there's insufficient EGR flow. It's on the intake-side of the system and if not enough exhaust-gases flow ...

p0401 code ' Toyota Nation Forum
Aug 14, 2021
P0401 egr ' Toyota Nation Forum
Jul 19, 2012
P0401 Testing EGR insufficient flow - Toyota Nation Forum
Jun 18, 2015
More results from www.toyotanation.com

P0401 : EGR Flow Insufficient on 1996 Toyota Corolla

OBD-Codes.com https://www.obd-codes.com > forums > viewtopic
Jan 20, 2007 - on EGR codes, we recommend replacing the EGR, vacuum modulator and VSV (if equipped) and cleaning out the carbon buildup to the intake from the ...
If that finds nothing wrong, remove the EGR valve and bypass tube and check them for cleanliness and blockages. If they are blocked, follow your maintenance manual's instructions for cleaning them out so you do not damage the valve, then replace them and reset the ECM.

Insufficient EGR Flow - P0401 Code - Toyota

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)

Read more at: https://www.obd-codes.com/p0401
Copyright OBD-Codes.com

The EGR valve is in a very difficult spot to work on. If the EGR is bad it will set off the check engine light and make the vehicle run rough or stall at idle. It really doesn't make it run rough while driving or accelerating. What are the conditions when the car runs rough?

if you manually push up on the EGR valve and the engine doesn't stall and the passages are all cleaned out then the problem is the EGR valve.

The code P0401 means P0401 Exhaust Gas Recirculation Flow Insufficient Detected.
__________
airbag reset tool also check fault code!

code p 0401 refers to exhaust gas recirculation (EGR) system--insufficient flow detected ===causes --hose leak/ blockage--basic setting not carried out if applicable ---wiring---EGR valve ---EGR solenoid --ECM
take it to an accredited service centre that has experience on your make of vehicle , tell them the fault details and get a proper diagnosis to determine the fault and a quote

I am not surprized. The chances that replacing an EGR valve will fix a code P0401 on ANY Ford vehicle is about 1/2 of 1 percent. You most likely either have clogged up EGR ports in your intake manifold, or you have a defective Delta Pressure Feedback EGR (DPFE) sensor.

To find out which it is, apply vacuum to the EGR valve vacuum port with the engine idling. The engine should stumble and/or stall. If it does not, your ports are clogged. If it does, the most likely cause of your problem is the DPFE sensor. However, the EGR vacuum control solenoid could also be the cause.
You cannot properly test the EGR vacuum control solenoid without the proper equipment, but you can check to make sure that there is manifold vacuum going into one side of the solenoid and you can check to make sure that there are no breaks or leaks in the line that runs between the solenoid and the valve. If you find any of these, repair as necessary. If you do not find a problem with the vacuum lines, then you can take a "guess" and replace the DPFE. If this does not work, then you can "guess" again and replace the solenoid. If it still does nort work, then you probably have a bad electrical circuit to the solenoid (once again, requiring the proper equipment to diagnose).

Please also review the following article: What Else Could Be Wrong?

it may help to tell what engine you have. P0401 doesnt mean the egr valve was bad, it means the egr isnt opening for some reason OR not flowing. Egr valves rarely are "bad" check if all vacuum lines are connected and clear. the egr vacuum solenoid is famous for being bad. als make sure the passage from the egr valve to the intake manifold is clean and flowing. Its like flushing a toilet thats clogged.. All the valves are working, but its not flowing.

Could be a EGR vacuum issue or temp sensor issue

Common Problems That Trigger the P0401 Code

• Restriction in the EGR passages, usually caused by carbon buildup
• Lack of a proper vacuum signal to the EGR Valve from EGR Vacuum Solenoid
  
• EGR Vacuum Modulator is defective
• EGR Temperature Sensor is defective
• EGR Valve is defective

This is from:
http://repairpal.com/OBD-II-Code-P0401-Ford

1. po401 refers to an insuffient flow of EGR gasses
2. locate egr valve
3. with engine running at idle
4. on the underside of the valve you can access the diaphram.
5. wearing glove if ness
6. lift diaphram while idling
7. does engine stall or run very rough?
8. if not remove valve
9. start engine
10. you should hear a very large vaccum leak and exhaust noise
11. if either are missing investigate cause
12. if ok reassemble.
13. locate DPFE sensor
14. inspect sensor for damage
15. inspect hose to sensor for damage
16. replace sensor