2003 LINCOLN NAVI CODE P0401

Asked by Dog Nov 15, 2020 at 07:39 PM about the 2003 Lincoln Navigator RWD

Question type: Maintenance & Repair

12 Answers

I was wondering if anyone can help me solve this puzzle I keep getting CODE P0401 I replace EGR sensors, hoses EGR VALVE I clean out the throttle body I put in a new EGR Valve Control Solenoid. Why is this code P0401 keep coming back?

3,240

Possible vacuum leak running to egr valve, o2 sensor, differential pressure sensor, manifold absolute pressure sensor, an issue with the pcm (requiring an update for example), or even a wiring issue

I try 2 brand new differential pressure sensor and still getting this code coming back. May be I should look into getting a new PCM computer?

3,240

Before going out and sinking more money in, check the vacuum lines and wiring

3,240

Runs from intake manifold to egr valve...of it's a vacuum leak it could even be on a line that t's off of it

Ok I found a broken hoses and I replaced it clear code did a driving cycle and notices 5 inc CATALYST, EVAP SYSTEM OXYGEN SENS HTR, MON AND EGR/VVT SYS. in which 3 out of the 5 went away with one of them being the EGR at this point there is not check engine light on however when the EGR/VVT CLEAR OK check engine light came back on p0401

3,240

Best guess on p0128 would be thermostat stuck open or bad coolant temperature sensor

3,240

As for p0401 code, attached a list of possible causes to track down the cause

That same hoses got brittle I just replaced it with a better one from the Auto Part store. I reset the code lets see what happens when I take it for a drive cycle and once it's complete.

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