NETWORKING: CAN COMMUNICATION SYSTEM (for Gasoline Model): Check Bus 2 Line for Short to +B; 2019 MY Corolla Corolla Hatchback GR Corolla [06/2018

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and +B when there is no resistance between terminal 18 (CA4H) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 17 (CA4L) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.

Symptom

Trouble Area

There is no resistance between terminal 18 (CA4H) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 17 (CA4L) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.

Short to +B in CAN main bus line
Short to +B in CAN branch line
Central gateway ECU (network gateway ECU)
ECM
Transmission control ECU
(for CVT(K120))
No. 4 CAN junction connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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.
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Before measuring the resistance of the CAN bus, turn the engine 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 (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.
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After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the engine 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.
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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

Tester Connection

Condition

Specified Condition

Connected to

I95-8 (CANH) - I26-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

Transmission control ECU*

I95-19 (CANL) - I26-16 (BAT)

I95-9 (CANH) - I26-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

Central gateway ECU (network gateway ECU)

I95-20 (CANL) - I26-16 (BAT)

I95-10 (CANH) - I26-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

ECM

I95-21 (CANL) - I26-16 (BAT)

Result

Proceed to

NG (Line to Central gateway ECU (network gateway ECU))

NG (Line to ECU or sensor)

Tester Connection

Condition

Specified Condition

I95-9 (CANH) - I26-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

I95-20 (CANL) - I26-16 (BAT)

(b) Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the bus line shorted to +B is connected.

Tester Connection

Condition

Specified Condition

I53-18 (CA4H) - I26-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

I53-17 (CA4L) - I26-16 (BAT)

HINT:

If the resistance changes to 6 kΩ or higher when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.
If the resistance does not become normal when the connector is disconnected from the ECU or sensor, check for a short to +B in the wire harness and repair or replace the wire harness or connector if necessary.