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James, Ford Technician
Category: Ford
Satisfied Customers: 3628
Experience:  Ford Senior Master Tech, Ford gas and diesel expert, ASE Certified
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F350 70th anniversary: So I am getting a p101 and p404 code.

Customer Question

So I am getting a p101 and p404 code. I cleaned and tested mass air flow sensor and replaced Egr valve... it was pretty bad. Code does not trip until it turn ignition off and on again. Can you help?
Submitted: 1 year ago.
Category: Ford
Expert:  James replied 1 year ago.
Hello, what engine do you have in this vehicle?
Customer: replied 1 year ago.
Expert:  James replied 1 year ago.
6.4L diesel? do you have the vin number by chance?
Customer: replied 1 year ago.
Customer: replied 1 year ago.
77k miles on truck
New air filter
3800 sence last oil change
23000 sence fuel filter
Possibly getting some fuel leakage into the oil.... :/
Customer: replied 1 year ago.
Also had radiator and fan clutch replaced recently
Expert:  James replied 1 year ago.
The mass air flow code can cause the P0404 code. I would try and clean the mass air flow cleaner first. are you using the factory air filter?
Customer: replied 1 year ago.
Already cleaned mass air flow sensor. I put in a nappa gold filter but factory intake system yes
Expert:  James replied 1 year ago.
Most likely the egr valve is bad but that won't cause the p0101 code.
Expert:  James replied 1 year ago.
As for the P0101 if cleaning the sensor makes no difference replacing it will correct this code/
Customer: replied 1 year ago.
Egr valve i replaced. Sensor tested good
Expert:  James replied 1 year ago.
how did you test the mass air flow sensor?
Customer: replied 1 year ago.
With multi meter. Watched the voltage go up and down with increased flow of air to motor.
Customer: replied 1 year ago.
Walk me through how to test it again. I will do it again make sure.
Expert:  James replied 1 year ago.
That's a good way to test it but with a performance code it's almost impossible to test without a scan tool and monitor the air flow. The problem with the code it's hard to diagnose because it might only go out of range at a certain speed while driving. Unless there is a damaged pin in the mass air flow sensor connector a new sensor has a 99% chance of repairing the issue