Codes for 1988 Mercury Cougar

1988 MERCURY COUGAR
85,556 MILES • 2WD • AUTOMATIC
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DISCENNA57
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Hi I was wondering if anyone can tell me what these codes mean and what I should do to fix the problem?

Code 12 - Cannot control RPM during self check or Idle speed control problem

Code 21 - Coolant temp out of range

Code 51 - Coolant temp sensor voltage too high or open circuit

Thanks!
Feb 20, 2011 at 12:52 AM
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RASMATAZ
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Try replacing the engine coolant temperature sensor and go from there-
Feb 20, 2011 at 12:56 AM
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DISCENNA57
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Ok thats what I was thinking but I did replace both the sensor and sender about a year ago. I dont know if that helps with anything, but my car has been very hard to start and its having trouble idling.

Thanks alot for your help.
Feb 20, 2011 at 8:48 PM
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RASMATAZ
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Recommend you check fuel pressure with a fuel pressure gauge if its within specs-could be leaking down
Feb 20, 2011 at 10:42 PM