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DTC P1601 - Communication Line Error (Automatic Transmission): Condition

DTC is set when signal voltage from Transmission Control Module (TCM) to Engine Control Module (ECM) is too high. Possible causes are:

Open or short circuit between terminal No. 2N on TCM and terminal No. 2H on ECM.
Open or short circuit between terminal No. 1K on TCM and terminal No. 2G on ECM.