"Engine Malfunction" on radio for 2012 Fiesta S sedan

I have since replaced the O'Reilly Auto Parts black brake switch with a Motorcraft one. STILL cannot get rid of the wrench with ForScan no matter what I try. I honestly am at a loss. And it's making me mad.

Any word on that blue one?

I'm thinking it better to replace both at the same time...

Why?

When you took pictures of that switch, the plunger was still fully retracted - while it was out. As in, there was no tension, nothing keeping it in - just the plunger itself was "stuck" in this position - even when you took it out.

So it is my fear that the Blue plunger - being that it uses a shaft lock mechanism - that when it was put in by someone before you got it in this condition, damaged that plungers "lock".

Why? "Lock"? Well, the plunger being that color means it has a special purpose, and the lock function, was to show it is"engaged" when it's seated in it holster.

How? You did show me it was seated, and when you took it out - it was still fully retracted, it would be sticking out until you pressed the plunger all the way in, and then "turned" the locking tabs that keep the spring tension-ed until you seat the plunger into the holster, turn that 1./4 turn, and "snap" out comes the plunger.

Your black one works -plunger comes out ... it's why the Brake Light works

Blue one taken out - still stuck all the way in...


Once those tabs on that shaft get pressed into the bracket, meet the flange when you twist the switch to mount it, fasten it, to the mount location. This action then presses the two white tabs you see on your plunger - into the body of the switch. It work much like a locking ring, the press in, twist to seat - action lets the tabs release that plunger so it works.

I replaced the blue one with an aftermarket one once already. I just replaced the black one a 2nd time, this time with a Motorcraft switch. Still doing the same thing. So what you're saying is the blue one can still possibly be bad?

I will take some pictures of them tomorrow.

No - not "bad" just not releasing the plunger so the switch can be used.

I've got down into the pedal assembly on my car and found some things out too, and even I don't appreciate this. I found stuff that may interest you...you may already know, but if you're having problems with the switch plungers not working right - I have some ideas to help you...

Black plunger

Ford Part: 3M5T-13480-AC - Brake Light Switch (Black Body) Normally Open - Closes On Plunger Out

Fords Replacement:


Blue one...

Ford Part: AA6T-9C872-AA (Blue Body Switch) Cruise Control Disable (Normally Closed - Opens when Plunger out)


I guess you came along at the right time. For I found my Brake Light Switch needs replacement too.


Both of these are shown with their tabs and plunger Locks off - meaning that the plungers are active to work the switch inside their body. This makes the plunger appear shorter and have some resistance to indicate the switch and it's return spring are engaged.

This is brutal...


So my Brake Light Switch had to be manually reset so I could do these photos and verify that the switch is working.

The Blue one still has tabs and the LOCK still present - looks a little beat up but this is +5-years down the road since they did any work on the pedals...(Warranty - discovered loose flange nuts under car so brought car in for inspection) Found that the Master Cylinder to Brake booster nuts were gone - the nut under the car fit this bolt - so they fixed loose hardware.


So upon further inspection - found the LOCK control sheared off the Brake Light Switch side, so I'll have to get one - will try locally.

However, you situation needs some more work. When the LOCK is not engaging the switch, the Plunger can go in and out all the way with little resistance to finger pressure - that means the switch inside is not engaged. So you'll have to turn (rotate or rotation act) using a narrow tip tool - screwdriver or similar and try to move that LOCK - with the plunger all the way in - to help engage the switch.

Once that is done, you'll see the Plunger sticks out, and has some resistance to it - but not ALL the way out with little resistance - this means the Plunger is set to work as a switch. To mount it, you may have to press the brake pedal down to the floor to make room so you can thread the plunger to it's mounting socket and align the tabs of the switch and press it in, flush, with 1/4 turn to hold it and mount the switch to it's socket. You can then verify it's hitting the paddle on the pedal and observe it's operation.

It seems that the "Service Now" warn message was due to the fact that the Blue switch, was not getting sensed as working - so it kills Cruise control and Hill Assist because it can't detect the switch by your pressing of the brake pedal - it would message you on the console asking you to press Clutch and Brake to Start - on starting.

Since clutch work was done - the Blue switch works OPPOSITE of the Brake switch - meaning it OPENS when you press the Brake Pedal (Affects Cruise Control and Hill Assist) and Closes when the Pedal is released - The Black Brake Stoplight Switch is CLOSED when you press the Brake pedal (Lights Brake Lights) and returns to OPEN (Brake Lights Off) when you release the pedal.

You might want to investigate that work...

Wow. I had zero clue about the lock mechanisms on these switches. So, installing them the way I did does not engage the locks? I simply installed them the way they were. Plunger loose...
Would it be better to remove the switches, engage the locks then reinstall them?

Since my switches got sheared, I had to verify that the plungers even worked those switches.

So I tried both the plunger all the way out and then the ones that were "set" and partially out. The Partially out ones worked fine so if you can set them; then install, it may be the best.

I've done several threads about Brake Light switch and set plunger so they work...once they're installed so they let you drive your car and things work like they should.

https://www.fordfiesta.org/threads/2014-fiesta-will-not-start-shift-out-of-park.8022/post-18823 - there are several suggestions in several posts in this thread.
https://www.fordfiesta.org/threads/manual-transmission-clutch-problem.7865/post-18125 - Another one with several responses.
https://www.fordfiesta.org/threads/dtc-code-p0809.8116/post-19684
https://www.fordfiesta.org/threads/...3-fiesta-sticks-while-driving.8383/post-22877

OK...before you ask the "Test" question, I used a DVM set to BEEP when shorts were detected.

To test, install them and see if you can access the connector. If you're careful you can remove the lower knee kick panel so you can access the switches easier.

The switches are easy enough to test using a thin tip probe to tap the wires. One wire is Grounded (Black-Blue Stripe) or Black Green-Stripe or Black Yellow Stripe - these wires should test to ground and make the tester BEEP and show low ohmic results. The other will only produce the BEEP when you press on the Brake pedal or vice versa - which the Blue Body switch BEEP when pedal is at rest and only BEEP when you press the Brake.

The Brake Pedal itself you can see the Brake lights reflected back to you if you're parked in a garage - they are bright enough so you can set their "Threshold" just by looking for when they light - then you can retest the Blue Switch and listen for the beep and adjust their aspects between both, so they work right for you.

You mean like this type of tester? I do not know how to work a multi-meter, even though I have one....

DVM stands for Digital Volt Meter

Like this...

Just a simple guy...
Since you were mentioning switches, this multi-tester will do the trick in seeing if the switches ground properly and work correctly as you apply the Brake pedal.

You can go elaborate and get Automotive types but with everything being what it is, the simpler testers work far better to the task of measuring simple On/Off like a switch - than to buy $1,000+ testers that are programmable and do many different things beyond Automotive...the little bugger above is less than $15 out the door - excluding Sales Tax...

Why not that Circuit Tester? Well, that would work and you may need it for those times you need to track down a blown fuse or somehow apply a load so you can detect current in a wire. So keep that one make sure it uses regular Filament bulbs - I've got a post or two around this forum somewhere describing why...

But the switches work as a Logic condition, so they operate more in a High-Impedance state to simply show Logic On Or Off so even the Brake light switch operates thru an amplifier inside the BCM (Body Control Module) - making them last longer because they have less power in current load thru them. So it's lifetime switch contacts ratings will last nearly the life of the car - but in my case they've been physically abused so new ones need to to be put in there.

So, I got in my car this afternoon after parking at Walmart to pick up a few things....and I'm driving down the road, maybe 15 minutes in..the wrench light is gone. The cruise control that I'd installed into my car is working. My Fiesta is a S sedan that did not come with CC.
I have NO clue what occurred. I remember turning the engine malfunction light off in the radio dash when I started my car when leaving Walmart, but I do not know how far into my drive it was before it shut off. I did not notice it until like 15 minutes into my drive...how silly of me. I was just driving, not really minding things as I had lots on my mind.
Before I got home, I turned off the rd, shut the car down, restarted it....NO wrench light. CC works. The only things I did was I changed out the new O'Reilly Auto Parts brake light switch for a Motorcraft one I got from Rock Auto, and I attempted 4 or 5 times with ForScan to delete the DTC P0504 code without success.
I am hoping the computer just reset itself...I do not remember how many times I've started my car since installing the Motorcraft brake light switch. For the moment, all is well.