I have a 2004 Ford Ranger 4.0 4x4 . I have been having to discharge
the Power Train Control Module quite frequently because my gas milage
starts declining. My concern in switching to an after market unit is
that i may get something that doesn't deliver the same mileage.
I get 19.5 mpg on a flat stretch of Highway where i live so i have been
able to eliminate all the variables that might normally affect gas mileage.

Have any of you been through this process. Suggest a brand possibly!

 

The 2004 Ranger was the first year of the HEC(hybrid electronic cluster) instrument panel
This means the cluster and PCM were "married" at the factory, so one can not work without the other, it was done to prevent Odometer swapping, i.e. selling high mile Ranger with a newly installed low mile odometer, fraud

So its not as simple as swapping out the PCM, a Ford dealer needs to "re-marry" the Cluster and PCM which involves duplicating odometer mileage to the new PCM
If you plug in a new PCM engine will not start, same if you plugged in a new HEC Cluster, no start

By discharging the PCM do you mean unhooking the battery?

It would be better to buy a Bluetooth OBD reader, under $40, and look at your long term fuel trims(LTFT) and short term(STFT)

Also older O2 sensors(over 100k miles, or 10 years) will cause false Lean voltage so PCM will run the engine Richer than needed so lower MPG

 

How do you know you get 19.5 mpg on a certain stretch of highway?

You also need to remember we are running "Winter Blend" fuel this time of year and that reduces mpg.

https://newsroom.aaa.com/2013/06/wha...lend-gasoline/

 

I did check all 4 02 sensors , Short and Long Term Fuel Trim, Mass Air Flow
etc. Everything checks out. Ford No Longer Produces The PCM.
I will have to look for a shop that has made the PCM exchange without
suffering any loss of mileage.
Thanks For Your Time.

 

When you get the PCM do not install it, take it to a Ford dealer and they will install it and then run the software to "marry" it to the cluster and PATS
Odometer is just one aspect of the process
And check with dealer first they may not want to do it

And if all the sensors check out why do you think its a PCM issue?
PCM issues is usually the PCM sensor circuit NOT working/reading correctly

 

Since my '05 has the HEC, would it make any sense to grab a PCM from a junkyard just to have in inventory should mine go bad?
I'll deal with "having them married" at a dealership when the time comes.

Also, are my 15 year old sensors suspect?

 

That sounds like a good plan if you are able to find one.

 

2005 Rangers don't have PATS which is good, Ford skipped a year
But yes the HEC and PCM do need to be re-married if either is changed

Only sensor that doesn't last are the O2 sensors, they have chemicals inside to measure oxygen levels and the chemicals get used up, expected life without major engine problems is 100k-150k miles

Second most likely to fail is the ECT sensor, but not expensive to replace and doesn't cause a No Start
If you are pulling parts at a wrecking yard then Ford IAC Valve is good to get, even used its better than new 3rd party

PCMs just don't fail that often, with the number of vehicles that use them the reported issues are so low that I wouldn't bother to get a "backup"