03 Ford F-150 Code PO125: Insufficient coolant temp for closed loop fuel control

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Old 01-17-11, 03:32 PM
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Question 03 Ford F-150 Code PO125: Insufficient coolant temp for closed loop fuel control

Had been noticing that my temp gauge (no actual temp "number" readings) has been on the low side (running cool) for a few months. I assumed it was a stuck open thermostat. Yesterday I got a "service engine soon" light. I scanned it and came up with the this code.
Code PO125: Insufficient coolant temp for closed loop fuel control.

google gave me this:

This means that the voltage from the temperature sensor is lower than expected, and is being ignored. The fuel management system stays at default settings similar to a cold start. The oxygen sensor is not being used to adjust the fuel mix and the fuel mix will likely be on the rich side. Also, depending on the system, the intake air pre-heater may stay on.

Causes:
1. Coolant temperature too low, engine does not come up to temperature; Thermostat stuck open, or missing.

2. Temperature sensor failed.

If your engine appears to be warming up ok, then it is likely the temperature sensor. Typically, coolant temperature sensors may fail within 4 to 5 years.

Your engine may have 2 temperature sensors: one for the fan, and another for the fuel management system. Consult a repair manual.


Since the only way I can tell is that the heater doesn't get as hot as it used to I figure it must be a stuck thermostat? Any thoughts?
 
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Old 01-18-11, 05:57 AM
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That would be my first choice. Good troubleshooting logic. Also the thermostat is probably cheaper than the temp sender. Had this not long ago on my wrecker.
 
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Old 01-19-11, 03:28 PM
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Can you be telling me where the thermo might be on my f150? Last time I did one it was under the water neck on a small block chevy V8.
 
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Old 01-21-11, 06:55 PM
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easiest way it to follow the hose from the top of your radiator. where that intersects your engine that should be where your thermostat is.
 
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Old 01-23-11, 07:15 AM
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Probably like the Chevy. Last time we owned a Ford truck, it was a '92, but that's where it was. Like gnarf says, follow the top hose. Once you drain the radiator down a little remove the top hose at the engine and you should be able to see the thermostat in the housing. Good time to replace hose(s) if needed.
 
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