Empirer

I just replaced my MAF. i had codes PO171,PO174. i tryed new fuel filter cleaning the old MAF, and looking for vacuum leak, there are non. I got sick of looking for the issue, so i took it to ford and had them diagnose. Turns out to be a bad MAF and PCM calibration outdated. THey wanted almost 600 dollars to install, so i told them ill do it myself. Went and picked up a new one and put it in the truck, light turned back on in a few miles.

So my question is, do i need to reset the PCM? How do i do this? I pulled the neg off the battery and the fuse that is for the PCM power and im going to let it sit over night. Will this do?

Any help would be great, i got smog next month and i need to figure this out

SuzukiRider

You cannot "reset" the PCM. Its actually a reflash which updates the software on the PCM itself. On Ford or a shop that has an IDS can reflash the PCM. We typically charge $89.95 for a reflash.

Empirer

Is the reflash something that is done after every MAF replacement? Also, looking over the Ford report, i saw that they got a code my scanner did not. P1127.

SuzukiRider

Not necessarily. The reflash is probably the remedy of the issues and the MAF replacement is a "cover your *** part."

Im not familiar with the P1127 off the top of my head... whats the description?

Empirer

The code description is "Heated Oxygen Sensor Heater not on During KOER Test". Im assuming the "heated oxy sensor" is the MAF, which would mean its not turning on, faulty wiring causing it to ground out?

Bennyv83

The "heated oxygen sensor" would be your heated oxygen sensor.... Located in each of your exhaust pipes. Sounds like you need to replace it, after you find out which of the 4 is bad.
There is a heating coil in the sensor which brings it up to temp faster so it can sense properly how the engine is burning.

Empirer

How would i test these sensors? Simple voltage meter test?

jt351

You still have a vacuum leak, The dealer was just guessing. You do not need a reflash and probably not the maf either. there are some vacuum hoses on the very back of the intake, almost impossible to see but I have had a few trucks(04-08 3v) with lean codes due to the vacuum hoses in the back.

Empirer

I have the 4.2 v6, not a 3 valve engine. I dont know of a vacuum hose on the back side. I also dont hear any hissing and have already tried the carb cleaner trick on all gasket and vacuum lines. I will look in the morning for this vacuum line.

jt351, would you happen to have good diagram of the vacuum system? The one on the bottom of the hood is somewhat vague, when showing you where the hoses start and end


--Random info to add--
I dont know if this would make a difference, but when I clear the code it comes back on at random times, anywhere from 2 miles of driving to 30 miles of driving, very random.

BolletuH

Umm.... on a side note you can simply "reset" your PCM by disconnecting the negative battery terminal for longer than five or so minutes. This is basically known as putting the car to sleep.