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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23821
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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P0012F code while driving steady 65mph. Clleared it twice

Customer Question

P0012F code while driving steady 65mph. Clleared it twice but keeps coming back. Truck still seems to run fine, 6.4 with 3.77 gears and get about 12.7 mpg
JA: When did you last clean or replace your air filter? And are the oxygen sensors in good working order?
Customer: just had 100K maintenance done. Dont know about O2 sensors but air cleaner is new
JA: What is the model of your '77 Ford?
Customer: not a 77 2008 F250 SD 4X4 6.4 liter
JA: Are you fixing your F250 yourself? What have you tried so far?
Customer: just started happening. I am 300 miles from home so dont want to do any damage to truck. Just researching the code.
JA: Anything else you want the mechanic to know before I connect you?
Customer: cant think of anything
Submitted: 6 months ago.
Category: Ford
Expert:  david craig replied 6 months ago.

Hi Im David, I assume you mean P012F?

Customer: replied 6 months ago.
Expert:  david craig replied 6 months ago.

ok, thanks. be with you in a few

Expert:  david craig replied 6 months ago.
P012F means the difference in engine coolant temperature compared to the engine oil temperature threshold has been met, usually resulting in limiting the engine power. This number is ***** 12 - 14 degree difference, what usually happens is the coolant has rust formed and restricts the eot cooler and the engine oil overheats. The fix is replace oil cooler, check egr cooler, and chemically flush cooling system.Oil cooler efficiency monitor - DTC P012F stored and wrench warning lamp illuminated when the oil coolers efficiency drops below a specified threshold for a given speed and vehicle load condition.
Expert:  david craig replied 6 months ago.

do you still need assistance?

Customer: replied 6 months ago.
no more assistance is needed. Your answer, which would have cost me a lot of money, was not needed. I replaced the coolant reservoir cap and added a quart of coolant and the problem is gone. The key is that the engine was running fine as I stated. A bit disappointed with just answer.