Code P0401?

Tiny
BIG_BEN_20
  • MEMBER
  • 1997 FORD F-150
  • 308,800 MILES
My truck has been giving me problems with this code. It’s an EGR valve. I changed out the part it says. I cleaned out the throttle body to make sure nothing is clogged, and the code still comes up. I deleted the code, and it came back. I changed the DPFE sensor, and it did nothing. I’m trying to get rid of my check engine light so I can smog my truck.



Sunday, June 25th, 2023 AT 11:40 PM

5 Replies

Tiny
MATHGEN
  • MECHANIC
  • 128 POSTS
Hello,

Here is a quick and easy test for the EGR system:

1. Disconnect the vacuum hose from the top of the EGR valve diaphragm.
2. Hook up a hand-held vacuum pump to the EGR valve.
3. Start the engine and allow it to idle. Begin applying vacuum to the valve, 15-20 PSI.

The engine should begin to run rough, stumble and even shut off. This would indicate that the EGR valve and ports are ok and that a problem with the vacuum supply exists. There could be a damaged vacuum line or the EGR control solenoid and/or wiring.

If there is no change in the engine idle, then there is an issue with the EGR valve or clogged EGR ports in the intake plenum or manifold, depending on which engine you have.
I hope this points you in the right direction. Please let me know if I can be of further assistance.
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Monday, June 26th, 2023 AT 5:29 AM
Tiny
BIG_BEN_20
  • MEMBER
  • 3 POSTS
Hello Mathgen, so, I replaced the EGR valve and cleaned out my intake manifold the EGR ports were clogged so I cleaned them out and my code still came back on. I put on a new EGR pressure sensor because that is what my check engine light is. If it happens to not be the issue what else can I check? I need to figure out the problem ASAP.
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Tuesday, June 27th, 2023 AT 9:29 PM
Tiny
MATHGEN
  • MECHANIC
  • 128 POSTS
Okay, make sure the hoses for the DPFE sensor are in good shape, free of restriction and installed properly. There are two sizes, inside diameter, and they need to be installed on the proper ports. If those are ok, we should check the vacuum supply side. That includes the vacuum lines, EVR solenoid and related wiring. Could you please provide me with the engine size or the 8th digit of the VIN so I can obtain the correct diagrams? Thanks.
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Wednesday, June 28th, 2023 AT 10:01 AM
Tiny
BIG_BEN_20
  • MEMBER
  • 3 POSTS
It’s a 97 f150 4.6 litter v8.
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Wednesday, June 28th, 2023 AT 12:02 PM
Tiny
MATHGEN
  • MECHANIC
  • 128 POSTS
Great, thank you for that info. Let's check for voltage at the EVR solenoid. Disconnect the 2-wire connector from the solenoid and then turn the ignition to on. Measure voltage from the red wire to ground, you should get battery voltage. Since the PCM only commands the EVR solenoid on a warm engine while driving under light to moderate throttle, it can be hard to test the control side. We can test the BR/PK wire for a short to ground and short to power with KOEO. That's Key on Engine Off. If no issue is found, the next step would be to test for continuity from the EVR solenoid connector to the PCM connector. You will need to remove the battery and battery tray to access the PCM connector. Just test continuity from pin 47 of the PCM connector to the BR/PK wire of the EVR solenoid connector, anything under 5 ohms is good. You can also inspect the vacuum reservoir, lines and check valve while the battery tray is removed. I highlighted the EVR solenoid and related wiring. Let me know if this helps.
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Wednesday, June 28th, 2023 AT 4:36 PM

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