Toyota Corolla Cross: Lost Communication with ECM/PCM "A" Missing Message (U010087)

Toyota Corolla Cross (2022-2024) Service Manual / Drivetrain / K120f (cvt) / Continuously Variable Transaxle System / Lost Communication with ECM/PCM "A" Missing Message (U010087)

DESCRIPTION

The TCM communicates with the ECM via CAN communication.

If a problem occurs in this communication, the TCM stores this DTC.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
U010087	Lost Communication with ECM/PCM "A" Missing Message	No communication between the TCM and ECM for 1.25 seconds or more (1-trip detection logic)	Harness and connector ECM TCM	Comes on	DTC stored	SAE Code: U0100

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

U010087

Lost Communication with ECM/PCM "A" Missing Message

No communication between the TCM and ECM for 1.25 seconds or more (1-trip detection logic)

Harness and connector
ECM
TCM

Comes on

DTC stored

SAE Code:

U0100

MONITOR STRATEGY

Related DTCs	U0100: Lost communication with ECM/PCM Verify communication
Required sensors/Components	ECM
Frequency of Operation	Continuous
Duration	1.25 sec.
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not stored	None
Auxiliary battery voltage (1 sec. or more)	10.5 V or more
Ignition switch	On (IG)
Starter	OFF

TYPICAL MALFUNCTION THRESHOLDS

Communication signal

Lost communication with ECM/PCM

CONFIRMATION DRIVING PATTERN

HINT:

After repairs have been completed, clear the DTCs and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
When clearing the permanent DTCs, refer to the Clear Permanent DTC procedure.
Click here

Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the ignition switch off and wait for 3 minutes or more.
Turn the ignition switch to ON and turn the GTS on.
Wait for 3 seconds or more with the ignition switch to ON. [*1]
HINT:

[*1]: Normal judgment procedure.

The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.
Enter the following menus: Powertrain / Transmission / Utility / All Readiness.
Input the DTC: U010087.

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 memory limit

HINT:

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 normal judgment procedure again.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Perform the universal trip to clear permanent DTCs.
Click here
Perform registration and/or initialization when parts related to the continuously variable transaxle system are replaced.
Click here
Check that no DTCs are stored after performing initialization.
Click here
Inspect the fuses for circuits related to this system before performing the following inspection procedure.

PROCEDURE

1.	CHECK TERMINAL VOLTAGE (POWER SOURCE OF TCM)

(a) Disconnect the C80 TCM connector.

(b) Turn the ignition switch to ON.

Standard Voltage:

Tester Connection	Condition	Specified Condition
C80-1 (+B) - C80-2 (E1)	Ignition switch ON	11 to 14 V

(d) Turn the ignition switch off.

(e) Connect the C80 TCM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE OF TCM)

2.	CHECK HARNESS AND CONNECTOR (ECM - TCM)

(a) Disconnect the A47 ECM connector.

(b) Disconnect the C80 TCM connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
C80-18 (CAN+) - C76-40 (CANP)	Always	Below 1 Ω
C80-17 (CAN-) - C76-39 (CANN)	Always	Below 1 Ω
C80-18 (CAN+) or C76-40 (CANP) - Body ground	Always	10 kΩ or higher
C80-17 (CAN-) or C76-39 (CANN) - Body ground	Always	10 kΩ or higher

(d) Connect the C80 TCM connector.

(e) Connect the A47 ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - TCM)

3.	REPLACE TCM

Click here

4.	PERFORM REGISTRATION AND INITIALIZATION

for Registration: Click here

for Initialization: Click here

5.	CHECK DTC OUTPUT (DTC U010087)

(a) Clear the DTCs.

Powertrain > Transmission > Clear DTCs

(b) Turn the ignition switch off and wait for at least 30 seconds.

(d) Enter the following menus:

(e) Read the DTCs.

Powertrain > Transmission > Trouble Codes

Result	Proceed to
DTCs are not output	A
DTC U010087 is output	B

END

6.	REPLACE ECM

Click here

PERFORM INITIALIZATION

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