2.3L ('83-'97) Persistent P0125

[cstarbard]

Hi guys,

My truck set a P0125 on a really cold day. I cleared it figuring it was a fluke. It came back, and I noticed that the plastic body of the coolant temp sensor was physically broken. I put a new sensor in, and the code came back again. I noticed that the wires for the coolant temp sensor were bent at a sharp angle, and fearing that maybe a wire had been broken as a result of the sharp angle, I replaced the connector and made the wires longer. I did NOT clear the code this time, figuring that it would go away on its own, but the CEL/code remains.

Do I need to clear the code, or have I not found the problem yet? Any idea what the problem could be?

Like every other Lima 2.3 it runs fairly cold. In colder weather I rarely see the temp gauge get 1/5th up if that. However, it reaches 1/3-1/2 up the temp gauge on a warm-hot day if sitting or driving around town, so I haven't suspected thermostat stuck open. I did replace the thermostat a few years ago and the truck's temp has always shown this way on the gauge for as long as I've had it.

Thanks.

 

[RonD]

P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control

Always good to post definition of the code for those of us that don't have them all memorized, which is pretty much everyone, lol

ETC sensor will have a grey/red wire and a 2nd wire
ECT sender has a red/white wire, some times just the one, later years it can have 2, black/white wire

Yes, that code should reset if engine coolant warms up above 150degF the next time computer boots up for cold start

Did you use a 195degF thermostat the last time?

Can your OBD2 reader show you live data?
Would be good to see what the computer sees coming from the ECT sensor

On some years Ford put the ECT sensor on the heater hose of the 2.3l's, this means heater core needs good flow for computer to get accurate coolant temp reading
Does the heater blow HOT, or just luke warm?

 

[RonD]

One other thing came to mind

The 2.3l doesn't generate alot of heat to begin with, so the fan clutch being stuck on could be a bigger issue than say on a V6 engine

Cold engine, open hood and spin the fan, should be tight, will move but won't spin, its cold locked
Start engine and run it for 30 seconds, you should hear the fan noise change when it unlocks after 5-10 seconds

Shut off engine and try to spin fan now, should spin easily, its unlocked
If it doesn't spin easily then that's your problem, full time locked fan

The fan clutch engages from radiator heat, as the center of the radiator gets warmer it heats up the spring on the front of the clutch which closes valves inside that causes the fan blade part to spin closer to water pump speed(rpm) so locks the blades for more cooling as needed by warmer radiator
But these clutches can fail locked or unlocked
Locked causes too much cooling, but not very noticeable on a V6 or V8, its usually the noise of the fan that causes people to notice a full time locked fan, lol
On the 2.3l over cooling can show up on the temp gauge and P0125

Unlocked fan clutch fail is noticed as climbing temp gauge when driving slowly or when stopped, then temp drops back to normal when moving again, because there is air flow thru radiator again, that the unlocked fan was not providing

 

[cstarbard]

Hi Ron- thanks as always!

So, I don't recall if I used a 195 degree thermostat. What I can say is, after replacing the thermostat, I had 1-2 years afterward without any apparent issues from the ECT or the P0125. The code just appeared one winter day, I noticed the sensor was broken, and after replacing it, the code remains, and will return if I clear it.

Heater blows HOT

My ECT is not on the heater hose, it's near the thermostat housing, nestled between the ignition coil, timing cover, and upper radiator hose.

I have not looked at live data but I have that ability- I will do that and let you know what I find

My fan clutch is failed but unlocked, I believe. I turned it while engine was cold and it spins with little if any resistance at all. It spins the same way after truck is warmed up. Not great, but probably not the cause of or contributing to, the issue?

Here's the strangest part. My drive home from work is an all highway commute like 25 minutes long. The temp gauge climbs to 40% (the highest I ever see) while I'm cruising at like 60-70mph, and then falls back down when I am no longer cruising (like if traffic causes us to stop, or if I get off the highway). The gauge needle wiggles up and down a lot too while I'm cruising. Sort of erratic. I can't really make sense of that. Historically the temp gauge in my truck always fell right down to the minimum marking while cruising at highway speeds, which makes sense to me, from the ram air effect. Once I'm off the highway and driving around town the temp gauge falls. It's almost like the temp sensor is reading backwards.

The ECT was not a motorcraft part, it was just a part store brand. Is it possible the new sensor is just bad? It wouldn't be the first time a new part was junk out of the box.

 

[RonD]

It reads more like the thermostat is not opening and closing like it should, thats what stabilizes the temperature of the coolant

Start cold engine and feel heater hose and upper rad hose, both will be cold of course
Let engine idle for 3 or 4min and feel the hoses again
Heater hose should be warning up, upper rad hose should still be stone COLD
If upper rad hose is warming up then thermostat is open and it should be closed

At highway speed the engine generates more heat so thermostat will open more, then as you slow down and stop the engine generates less heat so thermostat will close a bit as coolant temp drops
It should balance out, not alot of needle movement
So what you describe seems like thermostat is stuck open, can't close all the way to maintain minimum temp, which should be about 185 looking at ECT sensor data with a 195deg thermostat

Ford temp gauge has 210deg as 1/2 way so after warm up gauge should be just below 1/2, and it should stay there regardless of driving speed or when stopped
It WILL go up a bit if pulling a load or going up a long grade, but never drop after its warmed up

Thermostats are designed to "fail safe" so if they are faulty they are suppose to fail in the open position to prevent over heating


Faulty fan clutch wouldn't have your current symptoms
When these fail the classic symptom is temp gauge climbing when driving slowly or stopped, and temp then going back down when above 30mph and radiator has good air flow again
But your test does read like fan clutch may be failing

After engine sits over night the fan clutch should be lock, because oil inside it is thick so will be hard to spin, try to spin it
Start engine and you should HEAR the fan pulling in air because its locked, but for under 10seconds and it should unlock, shut off engine
If fan clutch is not locked after sitting overnight then its most likely bad
Or if its locked after engine has been started for say 20seconds and shut off, then its also bad

The fan clutch is locked and unlocked by radiator temp, on the front of the fan clutch is a bi-metal spring that expands as its heated which locks the fan blades so they spin closer to water pump RPMs pulling in more air
So as radiator heats up in the center part, that heats up the fan clutch spring, and thats what adjusts the lock and unlock once the oil in the fan clutch is warmed up(after 20seconds)

If your radiator is not all that hot because thermostat is stuck open then fan may not be locked because its not needed, so I would address the thermostat issue first, unless the fan clutch is not locked when cold, if its not locked then I would replace that as well