P0117 troubleshooting

[TruckTruck]

Hello to all-1st time posting. Thanks all in advance.

97 2.3 Ranger manual 2wd drive with this code yet no other codes accompany. Currently checking volta at PCM, where the PCM Wires/plug meet by fuel rail/air intake mani and at the ECT plug. Changed coolant and ECT. It did state it was intermittent a while back though just the one code now.

 

[RonD]

Welcome to TRS

So we are on the same page: P0117 Engine Coolant Temperature Circuit Low Input

Good to look up Codes on a full list as computer has many to chose from for EACH sensor or Control, list is here: https://www.therangerstation.com/tech_library/OBD-II_codes.shtml

Swapping the ECT sensor when you get this code is OK, these do seem to fail now and then
BUT ONLY if your dash temp gauge seems to be working OK, i.e. after cold start Dash gauge shows cold and then after 5-8 min of driving temp gauge is up above a 1/3 on a 2.3l, close to 1/2 on a V6

P0117 can be caused by thermostat stuck open so engine doesn't warm up, so dash temp gauge would always read lower than its used to

Fuel injected engines had TWO temps units until the mid-2000's
ECT sensor, 5volts always 2 wires
Temp Sender, 12volts 1 or 2 wires, one will be a red/white stripe wire, in Rangers and most Fords

Temp sender is for the dash board temp gauge and has been used since 1930's or so

ECT sensor was added for fuel injection, can't use a Choke Plate with fuel injection, no Jets, but gasoline engines all need to be choked on cold start
ECT sensor is more accurate than sender, so computer can do just the right amount of choke based on cold start temp and then through warm up it can ease off the choke

The computer times engine warm up by watching the ECT temp increase when engine is running, it expects temp to be above 140degF within 8 minutes at least
If its not warming up then computer will set this code
So could be cooling system is running colder than it should as well as a failing ECT sensor

ECT sensor just reports the temp, it doesn't control it
So any time you get any code don't blame the sensor, in this case it could be reporting low temp because temp IS Low so sensor is working as it should
If your heater is not as hot as it used to be or dash temp gauge is lower then check cooling system


First thing is to make sure you change the right temp unit, ECT sensor will be front top area of the 2.3l engine
SENDER is drivers side rear near oil pressure sender

Graph of voltages base on ECT temp here: https://www.freeautomechanic.com/images/ect3.gif
ECT has 2 wires one is 5volt and that wire is SHARED with all the other sensors, so if its bad then there would be ALOT more codes, lol
The "out" wire is what you test, use a sewing needle to pierce the wire to test voltage
Cold engine should be about 3volt depends on outside temp of course, see graph
After startup voltage should start to drop lower and lower as coolant/engine warms up
Just under 1volt after 8 minutes

 

[TruckTruck]

Hey Ron-Thanks for the reply. I read another thread where you stated some of the above.

I’ve changed out the plug for the ECT, IAT as well as the ECT itself about a month ago. Plug wasn’t “snapping” into place. It’s not a motorcraft, so not sure if that would do. Same with ECT and IAT replacement. I’ve put on my scanner while starting to see how much or if it moves. Today it actually slowly went up. Faster than IAC numbers though. I’ve pulled the plug while it’s been running to see the -40* show up and then reconnect the plug to watch it go back up.
No other codes are present as I’ve stated.

 

[TruckTruck]

Temp gauge seems to be working fine. Slowly goes up and never in the danger zone. Always seems to sit just under 1/2 way up.

 

[TruckTruck]

Upper rad hose does get warm. Heater blows pretty warm air. Not blaming anything. Just adding info as I think of it to help diagnose from afar.

 

[RonD]

Did the new ECT sensor look like this: http://www.grandmarq.net/oldfuelinjection/images/ect.jpg
Cone shaped tip in coolant

Senders have a cylinder shape end, like this: https://i.ebayimg.com/images/g/qq0AAOSwuZVcLeGD/s-l400.jpg

Did you get a chance to test the wires?


If the connectors don't fit then you either got the wrong units or will need to change the connectors to a newer style, although I wouldn't expect that on a 1997, 1987 maybe but not 1997

 

[TruckTruck]

Nope. I was just reading up on that and liking at pictures just before you posted Ron. Seems like a swap of the sensor could resolve it all. I’ll report back with what I find.

 

[TruckTruck]

Is there a p/n I should be looking for?

 

[RonD]

Have a read here: https://www.ranger-forums.com/2-3l-2-5l-i4-tech-31/97-ect-sensor-sender-149526/

 

[1990RangerinSK]

ECT sensor was added for fuel injection, can't use a Choke Plate with fuel injection, no Jets, but gasoline engines all need to be choked on cold start
ECT sensor is more accurate than sender, so computer can do just the right amount of choke based on cold start temp and then through warm up it can ease off the choke

Call me picky, fussy, or whatever, but this irks me. You keep referring to a "choke", when fuel injected engines don't have a choke. You talk about choking the engine, setting the choke, etc.

There is no choke. There's a plate that closes to block air. I don't know what it's called, but it is not called a choke.

Can we please teach modern/correct terminology? You say "the engine needs to be choked for cold start". It's EFI, can't choke it, because there's no choke.

OPEN LOOP: This is the mode the computer runs the engine in when the engine is first started. The O2 sensors are not read to determine how rich the engine is running. The engine runs as rich as possible, similar to closing the choke on a carbed engine.

CLOSED LOOP: O2 sensors are functioning, telling the computer whether the engine is getting the right fuel mixture, and the computer adjusts accordingly. The engine will operates in CLOSED LOOP once it is up to operating temperature, and runs as lean as possible, adjusting as necessary (similar to opening the choke on a carbed engine.

 

[RonD]

For gasoline engines "choke" means Richer air/fuel mix and usually a higher idle

Most people identified that as a Choke Plate on a carburetor, which provided the rich air/fuel mix by limiting air intake so more fuel is sucked from the Jets, and also set a cam for higher idle

I say it in my way more for people to understand that fuel injection needs to be "choked" just like any gasoline engine when its cold
Meant no offense by it

Open Loop just means computer is using internal tables for air/fuel mixes
If engine is cold then its also using Choke based on temp
But it can be in open loop after warm up if there is a main sensor fault

Yes, closed loop is when O2s are heated up and computer can do air/fuel calculations on the fly

 

[1990RangerinSK]

For a gasoline engines "choke" means Richer air/fuel mix and usually a higher idle

Most people identified that as a Choke Plate on a carburetor, which provided the rich air/fuel mix by block air intake so more fuel is sucked from the Jets, and also set a cam for higher idle

Right.

I say in my way more for people to understand that fuel injection needs to be "choked" just like any gasoline engine when its cold
Meant no offense by it

Actually, what both need is to "run rich" which, on a carbed engine is accomplished by closing the choke ("choking").

Open Loop just means computer is using internal tables for air/fuel mixes
If engine is cold then its also using Choke based on temp
But it can be in open loop after warm up if there is a main sensor fault

Yes, closed loop is when O2s are heated up and computer can do air/fuel calculations on the fly

If I'm not mistaken, those internal tables cause the engine to run rich.

For people reading this who need an explanation, running rich means that the engine is getting more fuel than air. You're essentially dumping raw fuel into the intake.

In order to start a cold engine with a carb, you had to set the choke. This was accomplished by a knob on the dash (manual choke) or by quickly pressing the gas pedal to the floor and releasing (automatic choke). Once the engine starts, an automatic choke opens on its own as the engine warms up, using a spring that operates the choke as the spring warms up from engine heat. On a manual choke, you would gradually adjust the knob (or, for some, that had three positions, push it in one "click" once the engine starts, and then another "click" once the engine warms up).[/QUOTE][/QUOTE][/QUOTE][/QUOTE]

 

[RonD]

Not sure what all that means but OK and well said

 

[TruckTruck]

Thanks for all the help. Electrical was solid all around. Connections, plugs and wires as well as readings on the voltmeter. Was a bad ECT. Swapped out and instantly made a difference.