Toyota CH-R Service Manual: Check Bus 2 Lines for Short Circuit

Toyota CH-R Service Manual / Networking / Can Communication System / Check Bus 2 Lines for Short Circuit

DESCRIPTION

There may be a short circuit between the CAN main bus lines and/or CAN branch lines when the resistance between terminals 18 (CA4H) and 17 (CA4L) of the central gateway ECU (network gateway ECU) is below 54 Ω.

Symptom	Trouble Area
Resistance between terminals 18 (CA4H) and 17 (CA4L) of the central gateway ECU (network gateway ECU) is below 54 Ω.	Short in CAN main bus lines Short in CAN branch lines Central gateway ECU (network gateway ECU) ECM

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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 ignition 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 ignition 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 blind spot monitor system on using the blind spot monitor main switch (ON/OFF switch), turn the cruise control main switch on, turn the LDA main switch on and then drive the vehicle at a speed of 60 km/h (37 mph) or more for approximately 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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Before replacing the ECM, refer to Registration.*1
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*1: w/ Smart Key System

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 SHORT IN CAN BUS LINES (CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

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

(b) Disconnect the central gateway ECU (network gateway ECU).

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
F74-18 (CA4H) - F74-17 (CA4L)	Cable disconnected from negative (-) battery terminal	108 to 132 Ω	ECM

Front view of wire harness connector

(to Central Gateway ECU (Network Gateway ECU))

to ECM

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)

2.	CHECK FOR SHORT IN CAN BUS LINES (ECM - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

(a) Disconnect the A38 ECM connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
F74-18 (CA4H) - F74-17 (CA4L)	Cable disconnected from negative (-) battery terminal	1 MΩ or higher

Front view of wire harness connector

(to Central Gateway ECU (Network Gateway ECU))

to ECM

REPLACE ECM

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (ECM - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

Open in One Side of Bus 1 Branch Line

DESCRIPTION When the CAN bus main lines are normal (no open, short to ground, short to +B or short between lines) and there is an ECU or sensor on the "Communication Bus Check" screen t ...

Open in Bus 2 Main Bus Line

DESCRIPTION There may be an open circuit in one of the CAN main bus lines when the resistance between terminals 18 (CA4H) and 17 (CA4L) of the central gateway ECU (network gateway ECU) is 70 Ω o ...

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