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If you're reading this, you likely need a new DPFE to potentially solve P0401 if your test from my previous write up came back defective.
So, in this write-up, I'll tell you how you can test these sensors at the junk yard really easy.
In case you missed it in my last writeup, these sensors operate on five volts. Peculiar, but they do. So to test these, we need a five volt supply. You're probably wondering where a guy (or gal), can find something around the house that can supply the voltage necessary. Thankfully there's a multitude of ways to do this, ranging from the common-man's solution to the 'resistor-geek' way. I'll start with common things that likely everyone has around their house and move up.
First method: AA batteries. You likely have some AA batteries around. You'll only need three for this, and if you don't, you can use some cheap ones from the dollar store. There are a couple ways you can put the batteries together but a cheap battery pack will do fine. Don't have a battery pack? Crack into an old battery-powered electronic device you don't use anymore, and cut its battery pack out. Simple and cost-effective. Alternatively, if you have a cheap Chinese flashlight laying around that uses the three, AAA battery pack, you can use that too.
Second method: USB, more specifically a USB power bank. USB devices of all kinds operate off 5 volts, which sits nicely within the sensor's comfort range. All you need is a cheap power bank capable of delivering at least 750 milliamps (this is what mine was rated for) and a cheap dollar store USB cable, or an old one lying around. It doesn't matter which. The cable I selected was an old USB to mini-usb cable, which nothing current uses anymore.
Cut the end off and reveal the four wires inside. They're likely red, black, green, and white mixed into some shielding. Cut the shielding away as well as the green and white 'data' wires. Those won't be used. Now strip the plastic off the red and black wires, power and ground respectively.
Don't have a USB power bank? You can get one cheap for less than ten dollars. Once you're done with it for this time, you can throw it in your glove box and keep it for those emergency times when you need a charge. Some also come with built in flashlights, so consider that too.
Method Three: Voltage Regulators. If you're familiar with electronics, you've likely heard of a voltage regulator. If you haven't but want to try this anyway, here's an excellent video explaining them and where you can get them; both online and out of old electronics you don't use anymore. Ironically this video also tells you how to build a phone charger, so I won't waste your time here. Simply replace the 12 volt battery he used for a 9 volt battery (assuming the former isn't laying around in your home), and you're good to go.
Now you should be armed with some kind of power supply that can give you five volts. No matter which method you use, the next part will be the same.
We'll be following the same wiring convention as in my previous write up, but going about it slightly differently. Several Ford vehicles use the same DPFE sensor. Late 90s to early 2000s Taurus's, Rangers of course, perhaps even F150s and the Windstar and Explorer too. Double check on Rock Auto or AutoZone to ensure the part numbers are the same, depending what vehicles are available at your local scrap yard.
Don't waste your time with the plastic DPFEs. Over time excessive heat and cold quickly make the plastic brittle, and you will almost always break the tubes off the DPFE; shoot for the aluminum ones instead. Not only will they not break, but metal is better anyway.
PS: The bolts holding them in place are likely either 7mm or 8mm nuts or bolts. Take an extension or two and maybe some special adapters to get into those tight places.
First, find a vehicle with a DPFE that's easily accessible. Don't make the job harder if you don't have to. I pulled three of them from Taurus's. They're low to the ground and the sensor is easily accessible at the rear of the engine closest to the firewall.
Once you've found one, take some wire cutters and snip the plug off, leaving you with enough wire for testing purposes. Strip back each individual wire and twist them around so they don't fray.
Now with your 5 volt power source, multimeter, and sensor, hook them up in this configuration. Bonus points if you use alligator clips.
As illustrated, both the supply and multimeter ground to the center wire, numbered '2'. The other lead on your multimeter clips onto wire numbered '1', and the positive wire of your power pack clips onto wire number '3'. With everything hooked up and turned on, suck on the ref hose as you did with your current DPFE and see your results. I recommend getting at least two, just in case one decides not to cooperate later on.
I hope this helped someone out there. It sure helped me when I learned this trick.