DTC U0100: Lost Communication with ECM / PCM: Description

This DTC is stored when a malfunction in the CAN communication between the power management control ECU and ECM is detected.

HINT:

When the power management control ECU is replaced with a new one and the cable is connected to the negative (-) battery terminal, the power source mode changes to on (IG).
When the battery cable is disconnected and reconnected, the power source returns to the mode it was in before the battery cable was disconnected.

DTC Code	DTC Detection Condition	Trouble Area	DTC Output Confirmation Operation
U0100	CAN communication malfunction between the power management control ECU and ECM (1-trip detection logic*).	CAN communication system Power management control ECU	Wait 4 seconds or more after turning the engine switch on (IG).

VEHICLE CONDITION AND FAIL-SAFE FUNCTION WHEN MALFUNCTION DETECTED

Vehicle Condition when Malfunction Detected	Fail-safe Function when Malfunction Detected
No effect on vehicle behavior.	CAN communication is normal and the engine speed signal from the direct line is abnormal: If the engine switch is pressed briefly, cranking stops when the starter OFF permission flag is received via CAN communication. If the engine switch is pressed and held, cranking stops according to the engine speed signal sent via CAN communication. CAN communication is abnormal and the engine speed signal from the direct line is normal: If the engine switch is pressed briefly, cranking stops according to the engine speed signal from the direct line. If the engine switch is pressed and held, cranking stops according to the engine speed signal from the direct line. Both CAN communication and the engine speed signal from the direct line are abnormal: If the engine switch is pressed briefly, cranking stops after 6 seconds elapse. If the engine switch is pressed and held, cranking is maintained for a maximum of 30 seconds.

Vehicle Condition when Malfunction Detected

Fail-safe Function when Malfunction Detected

No effect on vehicle behavior.

CAN communication is normal and the engine speed signal from the direct line is abnormal:

If the engine switch is pressed briefly, cranking stops when the starter OFF permission flag is received via CAN communication.
If the engine switch is pressed and held, cranking stops according to the engine speed signal sent via CAN communication.

CAN communication is abnormal and the engine speed signal from the direct line is normal:

If the engine switch is pressed briefly, cranking stops according to the engine speed signal from the direct line.
If the engine switch is pressed and held, cranking stops according to the engine speed signal from the direct line.

Both CAN communication and the engine speed signal from the direct line are abnormal:

If the engine switch is pressed briefly, cranking stops after 6 seconds elapse.
If the engine switch is pressed and held, cranking is maintained for a maximum of 30 seconds.