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Home >> Jeep >> 2021 >> Grand Cherokee L Laredo, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 25 (8HP75 Automatic Transmission - DTCS P1D79-00 To U1489) >> Diagnosis And Testing >> P1DF3-00: Ecu Not Initialized >> Theory Of Operation

Theory Of Operation

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The purpose of the diagnostic is to monitor the time period of the Electronic Shift Module (ESM) initialization state. The Transmission Control Module (TCM) receives the status of the initialization state from the ESM on the Controller Area Network (CAN) Bus while evaluating a counter in the TCM to determine if the initialization time is excessive.