U0101

DTC Code	DTC Name
U0101	Lost Communication with TCM

DESCRIPTION

The Transmission Control Module (TCM) and ECM perform 2-way communication with each other via the Controller Area Network (CAN). The TCM sends signals to the ECM concerning required engine speed, required engine torque, warning indicators in the combination meter assembly, DTCs and other data. The ECM sends signals to the TCM concerning engine speed, opening angle of the throttle valve, temperature of intake air, temperature of engine coolant, engine torque and other data. If the TCM cannot communicate with the ECM, the TCM will conclude that there is a malfunction in the CAN communication system, illuminate the MIL and store this DTC.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory
U0101	Lost Communication with TCM	All of the following conditions are met for 1.25 seconds (1 trip detection logic): Engine switch on (IG) Battery voltage 10.5 V or higher No communication between ECM and TCM	ECM to TCM circuit TCM ECM	Comes on	DTC stored

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

U0101

Lost Communication with TCM

All of the following conditions are met for 1.25 seconds (1 trip detection logic):

Engine switch on (IG)
Battery voltage 10.5 V or higher
No communication between ECM and TCM

ECM to TCM circuit
TCM
ECM

Comes on

DTC stored

MONITOR STRATEGY

Required Sensors/Components	ECM
Frequency of Operation	Continuous

CONFIRMATION DRIVING PATTERN

Connect the GTS to the DLC3.
Turn the engine switch on (IG).
Turn the GTS on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the engine switch off and wait for at least 30 seconds.
Turn the engine switch on (IG).
Turn the GTS on.
Wait 5 seconds or more.
Enter the following menus: Powertrain / Engine / Trouble Codes.
Read the pending DTCs.
Tech Tips
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: U0101.

Check the DTC judgment result.

GTS Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

Tech Tips

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform the Confirmation Driving Pattern and check the DTC judgment result again.

WIRING DIAGRAM


*a	from EFI MAIN Relay
*b	from P/I-B NO. 2 Fuse
*c	EFI MAIN
*d	CAN Communication Line

CAUTION / NOTICE / HINT

Note

Inspect the fuses for circuits related to this system before performing the following procedure.

Tech Tips

Read freeze frame data using the GTS. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC U0101)

Connect the GTS to the DLC3.
Turn the engine switch on (IG).
Turn the GTS on.
Enter the following menus: System Select / Health Check.

Read the DTCs.

Result

Result	Proceed to
DTC U0101 is output	A
DTC U0101 and other DTCs are output	B

Tech Tips

If any DTCs other than U0101 are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

CHECK TERMINAL VOLTAGE (POWER SOURCE OF TCM)

*a	Rear view of wire harness connector (to TCM)

Disconnect the TCM connector.

Measure the voltage according to the value(s) in the table below.

Standard Voltage

Tester Connection	Condition	Specified Condition
A28-6 (BATT) - A28-2 (E1)	Always	11 to 14 V

Turn the engine switch on (IG).

Measure the voltage according to the value(s) in the table below.

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
A28-5 (+B) - A28-2 (E1)	Engine switch on (IG)	11 to 14 V

Result

Proceed to
OK
NG

NG

GO TO TCM POWER SOURCE CIRCUIT Click here

OK

CHECK HARNESS AND CONNECTOR (TCM - ECM)

Disconnect the A28 TCM connector.
Disconnect the A13 ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
A28-21 (CAN+) - A13-9 (CAN+)	Always	Below 1 Ω
A28-13 (CAN-) - A13-10 (CAN-)	Always	Below 1 Ω
A28-21 (CAN+) or A13-9 (CAN+) - Body ground and other terminals	Always	10 kΩ or higher
A28-13 (CAN-) or A13-10 (CAN-) - Body ground and other terminals	Always	10 kΩ or higher

Result

Proceed to
OK
NG

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

REPLACE TRANSMISSION CONTROL ECU ASSEMBLY

Replace the TCM.

Click here

Result

Proceed to
NEXT

CHECK WHETHER DTC OUTPUT RECURS (DTC U0101)

Connect the GTS to the DLC3.
Turn the engine switch on (IG).
Turn the GTS on.
Clear the DTCs.

Powertrain > Engine > Clear DTCs
Turn the engine switch off and wait for at least 30 seconds.
Turn the engine switch on (IG).
Turn the GTS on.
Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
Enter the following menus: Powertrain / Engine / Trouble Codes.

Powertrain > Engine > Trouble Codes

Read the DTCs.

Result

Result	Proceed to
DTCs are is not output	A
DTC U0101 is output	B

A

END

B

REPLACE ECM Click here

SFI SYSTEM(w/o Canister Pump Module), Diagnostic DTC:U0101