PO401 "HELP" Tried everything
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Joined: Jan 2005
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PO401 "HELP" Tried everything
Have a PO401 Code, Found Fixes in forums. 2001 f150
First, I removed the trottle body and the ports were clogged, cleaned out the ports and cleaned trottle body, Reset code and next day engine light "PO401 Code"
Second, Replaced the DPFE sensor, Reset code, a week later engine light "PO401 Code" and I also had a loud vibration noise going from the air intake between the air filter and trottle body.
Third, replaced the EGR valve, I arlso removed and cleand the IAC valve, Reset Code, next day engine light "PO401 Code"
Have I missed something or left something out?
First, I removed the trottle body and the ports were clogged, cleaned out the ports and cleaned trottle body, Reset code and next day engine light "PO401 Code"
Second, Replaced the DPFE sensor, Reset code, a week later engine light "PO401 Code" and I also had a loud vibration noise going from the air intake between the air filter and trottle body.
Third, replaced the EGR valve, I arlso removed and cleand the IAC valve, Reset Code, next day engine light "PO401 Code"
Have I missed something or left something out?
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
P0401 seems to be an issue with vacuum and EGR. So I'd suggest checking for vacuum leaks, take a can of starting fluid or WD40 and spray around hoses and seals. If the engine revs up, you have found your leak.
After that it's time to replace the sensor.
After that it's time to replace the sensor.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
I would go thru a test procedure to be sure the EGR path is open.
Apply vacuum directly to the EGR and see that the engine will run rough, indicating the passages are clear and that it will close again ( engine smooths out.
Next, remove the DPFE and feel for exhaust puleses coming out of both small tubes as an indication these paths are open.
Next, inspect all hoses on the DPFE for correct hookup as they are two different sizes.
Check hose from the EVR to the EGR.
If all these check out, I would still suspect the new DPFE.
THE 401 low flow test checks the path and ability of the EGR to control flow by a diagnostic routine that pulses the EGR a percentage so the DPFE can measure the expected flow rate for pass or fail limits.
Apply vacuum directly to the EGR and see that the engine will run rough, indicating the passages are clear and that it will close again ( engine smooths out.
Next, remove the DPFE and feel for exhaust puleses coming out of both small tubes as an indication these paths are open.
Next, inspect all hoses on the DPFE for correct hookup as they are two different sizes.
Check hose from the EVR to the EGR.
If all these check out, I would still suspect the new DPFE.
THE 401 low flow test checks the path and ability of the EGR to control flow by a diagnostic routine that pulses the EGR a percentage so the DPFE can measure the expected flow rate for pass or fail limits.
