P0401 trouble code

[98v70dad]

Whats the most likely source of this code? It comes and goes (intermittent). I just replaced the camshaft position sensor and camshaft synchronizer and the code showed up after that. This truck was not well maintained and the check engine light had been on for about 19 years. It took a week after replacing the camshaft position sensor and synchronizer for P0401 to show up.

I noticed today when the check engine light came on the truck sort of lost power for a second after the code light came on ....

 

[RonD]

P0401 is insufficient Exhaust gas flow in the EGR system

PCM(computer) opens the EGR(exhaust gas recirculation) valve while driving, and it monitors how much exhaust is flowing into the intake using the DPFE(differential pressure feedback) sensor.
DPFE sensor has two hose connected, one closer to the EGR valve than the other, the pressure difference between these two hoses tells PCM how much exhaust is flowing into the intake.
Hoses can get clogged up, or even reversed, one is larger than the other and so are the ports they connect to.
Free to check the hoses for blockage or cracks.
Also its electrical connector, should be clean and dry inside, free to check

But most likely, common, cause for P0401 is failed DPFE sensor


It is also possible that vacuum hose to EGR valve is unplugged or EGR solenoid is failed or its vacuum lines are disconnected.
But the comment that you "lost power" at the time of the CEL coming on, to me, means the PCM opened the EGR valve too much to test why it was getting insufficient pressure difference, which causes loss of power, then it set code and will open EGR valve sparingly until system tests as OK

 

[98v70dad]

P0401 is insufficient Exhaust gas flow in the EGR system

PCM(computer) opens the EGR(exhaust gas recirculation) valve while driving, and it monitors how much exhaust is flowing into the intake using the DPFE(differential pressure feedback) sensor.
DPFE sensor has two hose connected, one closer to the EGR valve than the other, the pressure difference between these two hoses tells PCM how much exhaust is flowing into the intake.
Hoses can get clogged up, or even reversed, one is larger than the other and so are the ports they connect to.
Free to check the hoses for blockage or cracks.
Also its electrical connector, should be clean and dry inside, free to check

But most likely, common, cause for P0401 is failed DPFE sensor


It is also possible that vacuum hose to EGR valve is unplugged or EGR solenoid is failed or its vacuum lines are disconnected.
But the comment that you "lost power" at the time of the CEL coming on, to me, means the PCM opened the EGR valve too much to test why it was getting insufficient pressure difference, which causes loss of power, then it set code and will open EGR valve sparingly until system tests as OK

Thanks. I had everything you mentioned disconnected to replace the camshaft synchro lastv weekend. I'll double check all the connections. That said if I don't have them right it seems odd that it would take a whole week for P0401 to show up. What is the PCM... your last few sentences look like they could be helpful to me if I knew what you weretalking about.

 

[adsm08]

Thanks. I had everything you mentioned disconnected to replace the camshaft synchro lastv weekend. I'll double check all the connections. That said if I don't have them right it seems odd that it would take a whole week for P0401 to show up. What is the PCM... your last few sentences look like they could be helpful to me if I knew what you weretalking about.

Powertrain Control Module or PCM is the main computer that controls the engine and transmission.

 

[98v70dad]

Powertrain Control Module or PCM is the main computer that controls the engine and transmission.

Thanks. I reread his message and see that he defined it. Called the ECM on my volvo.

 

[RonD]

Yes, ford calls engine/trans computer a PCM, other names are ECU, EEC, and F*ing Computer, last is the technical term