NETWORKING: CAN COMMUNICATION SYSTEM (for HV Model): ECM Communication Stop Mode; 2020 MY Corolla Corolla HV [01/2019 - 04/2020]

Last Modified: 07-31-2024	6.11:8.1.0	Doc ID: RM100000001GVYP
Model Year Start: 2020	Model: Corolla	Prod Date Range: [01/2019 - 04/2020]
Title: NETWORKING: CAN COMMUNICATION SYSTEM (for HV Model): ECM Communication Stop Mode; 2020 MY Corolla Corolla HV [01/2019 - 04/2020]

ECM Communication Stop Mode

DESCRIPTION

Detection Item	Symptom	Trouble Area
ECM Communication Stop Mode	Any of the following conditions are met: Communication stop for "ECM (Engine)" is indicated on the "Communication Bus Check" screen of the Techstream. Click here Communication stop history for "ECM (Engine)" is indicated on the "Communication Bus Check (Detail)" screen of the Techstream. (The Lost Communication Time value for "ECM (Engine)" is 6 or more.) Click here Communication system DTCs (DTCs that start with U) that correspond to "ECM Communication Stop Mode" in "DTC Combination Table" are output. Click here	ECM main line or connector ECM branch line or connector Power source circuit of ECM ECM ground circuit ECM

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

NOTICE:

Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.
Click here
Before measuring the resistance of the CAN bus, turn the power switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) auxiliary battery terminal and leave the vehicle for 10 minutes or more before measuring the resistance.
After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.
Click here
After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the power switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes or more.
After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal.
Click here
Inspect the fuses for circuits related to this system before performing the following procedure.

HINT:

Before disconnecting related connectors for inspection, push in on each connector body to check that the connector is not loose or disconnected.
When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.

PROCEDURE

1.	CHECK FOR OPEN IN CAN BUS LINES (ECM MAIN LINE AND BRANCH LINE)

(a) Disconnect the cable from the negative (-) auxiliary battery terminal.

(b) Disconnect the A46 and C77 ECM connectors.

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

*a

Front view of wire harness connector

(to ECM)

-

-

Standard Resistance:

Tester Connection	Condition	Specified Condition
A46-13 (CANH) - A46-26 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	108 to 132 Ω
C77-31 (CAN+) - C77-32 (CAN-)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

Result	Proceed to
OK	A
NG (No. 2 CAN junction connector main line)	B
NG (No. 5 CAN junction connector branch line)	C

B

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (ECM)

C

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (ECM)

A

2.	CHECK ECM POWER SOURCE CIRCUIT

(a) Check the ECM power source circuit.

Click here

OK

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)