Overdrive light flashing, no other issues.
 

My overdrive light has been blinking off and on randomly for about 6 months or so. It never goes steady and there seems to be no rhyme or reason to when it does start flashing. Nothing runs differently when it is on or off; none of the gears feel rough at this point, since doing a fluid change and changing the spark plugs and wires. There had been a thunk sound when dropping to reverse and a slight jump when hitting third hard and fast (it's an automatic unfortunately...) But the fluid change fixed that to where neither feels abnormal at this point.

Just looking for some ideas on what it could maybe be. I need to get by the auto parts place and get the code read, but since it's such a random occurrence, it's either too late or I'm on my way to work when the light comes on.

I was going to purchase a code reader, but then was told most of the cheaper ones won't read tranny codes anyways.

Welcome to the forum

Codes are stored in memory so you can retrieve them anytime, OD light does not need to be flashing
Write down any code numbers, and have them Clear memory.

First thing to do is to see if OD(over drive) on/off works
Whenever you turn the key off and then on Computer resets to OD on(OD Light off)
When light is not flashing see if you can turn OD off(OD light on)
Then turn OD on(OD light off)

The OD button is just a 12volt momentary switch, so when computer "sees" 12v on that wire it toggles OD on or off, so each time you press the button OD switches to opposite of where it was before.

Flashing OD light is to tell driver there is an electrical transmission problem, and most likely a code will be set.
Transmission codes are P07xx, or P17xx

Bluetooth OBD2 readers are the best valve and the APPS are either Free or $5
These readers plug into the OBD2 port on ANY vehicle sold in the US or Canada from 1996 and up, so not a Ford thing or even US made thing.
They are powered from that port, no batteries.

You provide the Display, i.e. smartphone or tablet/laptop that has Bluetooth
And these are great for doing LIVE DATA, you can see engine data live while driving
If you get one get the extension cable with it, in some vehicles the OBD2 port is behind a small cover plate and Bluetooth device is too wide to fit in unless you remove the whole trim piece.

Check to make sure the Reader and APPS can read transmission codes, most can and a few can get airbag codes as well, but that has more to do with the computer system software than the reader itself.

Also what year Ranger do you have with what engine?
Above info is generic for vehicles 1996 and up

The overdrive will turn off and on as long as the light hasn't started flashing. Good to know that I don't need to wait for it to be flashing to get the code to show up!

It's a 4.0 6 cylinder, 4x4 automatic

Oh, and 2010

You have a 5R55E automatic transmission

4R55E is the same transmission, the 5R got the "5th gear"(faux 2nd gear) from a software change in the PCM(computer), it turns OD on while still in 1st, that gives driver a faux 2nd gear, making a 4-speed into a 5speed, very clever.

Point is whatever applies to 4R also applies to 5R55E, internally it is the same transmission


OBD2 code list here: OBD-II Trouble Codes : The Ranger Station

The "trick" in using on board diagnostics(OBD) codes is not really a trick just common sense but many pass it up.
NEVER Google a code number and expect to get a correct answer to what it might mean.

Look a code up on a complete list, and you will see several codes about the same part.
i.e. Turbine speed sensor
P0715 Input/Turbine Speed Sensor Circuit Malfunction
P0716 Input/Turbine Speed Sensor Circuit Range/Performance
P0717 Input/Turbine Speed Sensor Circuit No Signal
P0718 Input/Turbine Speed Sensor Circuit Intermittent

4 codes for this, each with slightly different angles on the problem
So knowing the codes the computer DID NOT PICK, helps to narrow down the problem.

P0xxx are generic/universal OBD codes
P1xxx are specific to car maker

So if you get code P1715 in a Ranger you would want to look that up on a FORD OBD list
If you got P1715 on a Tacoma you would look that up on a Toyota OBD List