Possible detonation theory?

[PKRWUD]

Capri-
If the ECT sensor doesn't tell the ECM that the engine temp is at least 50 degrees during KOEO, or at least 180 degrees during KOER, you will not pass the self test, and a code 21 will come up. In other words, if the KOEO and KOER self tests are performed correctly, the ECM will tell you if the ECT sensor is sending a signal implying the engine temp is colder than it is. This is why you will receive a code 21 if the engine isn't properly warmed up prior to testing. If it is properly warmed up, and you still get a code 21, then the ECT sensor is likely faulty.

Take care
~Chris

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Retired Moderator
MustangNet

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RACECAR spelled backwards is RACECAR

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