Codes for 1988 Mercury Cougar

1988 MERCURY COUGAR
85,556 MILES • 2WD • AUTOMATIC
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DISCENNA57
  • MEMBER
  • 8 POSTS
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 19, 2011 at 4:52 PM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Try replacing the engine coolant temperature sensor and go from there-
Feb 19, 2011 at 4:56 PM
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DISCENNA57
  • MEMBER
  • 8 POSTS
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 12:48 PM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Recommend you check fuel pressure with a fuel pressure gauge if its within specs-could be leaking down
Feb 20, 2011 at 2:42 PM
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