OBDII Code List

U0101 TOYOTA - Lost Communication With Transmission Control Module

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3   
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Possible causes

  • Faulty Transmission Control Module (TCM)
  • TCM harness is open or shorted
  • TCM circuit poor electrical connection
  • Faulty Engine Control Module (ECM)

Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

U0101 Toyota Description

The Transmission Control Module (TCM) and Engine Control Module (ECM) perform 2-way communications with each other via the Controller Area Network (CAN). The TCM sends signals to the ECM concerning required engine rpm, required engine torques, warning indicators in the combination meter, DTCs and other data. The ECM sends signals to the TCM concerning engine rpm, opening angles of the throttle valve, temperature of intake air, temperature of engine coolant, engine torques and other data. If the TCM cannot communicate with the ECM, the TCM will conclude that there is a malfunction in the CAN system, illuminate the MIL and set a DTC.
OBDII Code U0101 Toyota - Lost Communication With Transmission Control Module  -

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