U0401 Error in my Ford Fiesta S 1.6 2012

[renz]

Last week, when I started my Ford Fiesta S 1.6 2012, it showed a check engine, traction control light, and hill start assist on my dashboard. The RPM of my car has been unstable.



I have a portable scanner and returned a P0351 Ignition Coil A Primary / Secondary Circuit error. I had the ignition coil replaced at a local mechanic. After replacing the ignition coil, the misfiring seems to be fixed:



But when the mechanic had it scanned again, it showed two more errors: U0401:00-2B and U0401:00-2F


Has anyone encountered the same problem? And what did you do to fix this?

 

[Handy Andy]

It's the P0351 - are the plug wires ok?

The process to even detect this code requires a misfire - but the way it can detect this is thru various methods and it uses the output of one sensor to help detect misfires - but the way the plug wires fire - affects the output in a different way when one cylinder misfires on a regular basis making the other sensor see rich fuel conditions

Sometimes it can only guess because it sees the same result every time it looks for results.

It's letting you know that the spikes in the primary for each plug - it sees a different result on one - all the time. Or, its sending a signal but it doesn't seem to be pushing the spark into the plug to fire it.

You replaced the module, but did you check the boots, plug and or the wire and check for continuity in the wire, into the booth and it's connector to the top of the plug?

 

[renz]

The mechanic checked the high-tension wires and said they are still fine.

I just had the fuel pump strainer replaced and cleaned the throttle body as recommended by a local mechanic, as sometimes it resolves the problem. After that, I scanned my unit using my OBDII and threw a new pair of errors -- P0017 and P0335. I still need to have it scanned with a better scanner and check if the U0401 is still there.

What confuses me is that I had that pair of errors before (that was last December, I think). What the mechanic did back then was to retime the belt (the timing belt was off when the mechanic checked my unit), and it fixed the P0017 and P0335 errors. I need to bring it to a mechanic and have it scanned again to check for errors, check if the timing belt is off again, or if the crankshaft sensor is the problem.

I'll keep this post updated until I fix the issue.

 

[Handy Andy]

This is good news!

You have a mechanic that can take the Fuel pump apart - find the strainer, it's filter media - and change it.

Fantastic.

Every time I've asked Ford here locally, they cannot give me any answers except for the pump itself is a sealed unit and has non serviceable parts, you simply change it - it is easier they say. To some it makes sense because the entire unit has aged together and to simply take it apart to change the media and clean it up might not last for long or as long for it to be worth the effort to do this type of filter media change. It can leave you stranded and left having to pay for another one anyways - so "Why go thru all that only to get stranded later when you need it the most?"

But to help others not in the USA - can you post those strainer and media Part-Numbers please?

Keep us posted on this - you've been a big help for the rest of us here living under the Ford umbrella...

Since you're having issues with timing, there are several threads here on this forum that might help. But keep us posted on the progress you're making on resolving this condition.

 

[renz]

I watched the mechanic remove the fuel pump, which is located under the backseat. He twisted off the metal ring covering the fuel tank using a special tool, as it's quite difficult to remove by hand, though you can try if you’d like. You can also refer to this video for guidance: How to replace fuel pump assembly 2011-2019 Ford Fiesta

Then, inside the fuel pump assembly is the strainer. You have to loosen some parts of the fuel pump assembly to access the filter media (no need to disassemble). Somewhere around the part I highlighted in the image below:



I bought the strainer through an e-commerce platform in our country: Fuel Pump Filter Strainer for Ford Fiesta
The price is ₱306 or around $5-6.

I'll try to visit the mechanic again this weekend to have the car scanned for more accurate diagnostics and to check whether the belt needs to be retimed or if there's an issue with the crankshaft position sensor. I’ll continue updating this post until the issue is resolved, to help others who might be facing the same problem.