Multiple error codes

Tiny
PSMITH123
  • MEMBER
  • 1989 MERCURY MARQUIS
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 130,000 MILES
Code 21
Code 33
Code 18
Code 74

What are these and what do do about them?
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Tuesday, December 10th, 2019 AT 10:23 AM

1 Reply

Tiny
AL514
  • EXPERT
Hello, the code 21 is coolant temperature sensor out of range, code 33 is EGR valve did not open/respond during self test. Code 18 is base timing needs to be checked, and code 74 is Brake On Off signal open or short to ground, so the brake switch on the pedal. Each of these issues will have to be diagnosed separately, none of them seem to be related. The coolant sensor most like just needs to be replaced as long as the wiring to it and the connector are in good condition. The EGR valve will have to be tested to see if it opens and closes properly. Most of the time there is just carbon build up around where the valve seats and can be scrapped off. The base timing issue can happen if the distributor has loosened up and has shifted the ignition timing. And last, the brake pedal switch should be inspected because of where it's located. It takes some abuse being on the brake pedal itself.
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Tuesday, December 10th, 2019 AT 2:50 PM

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