CAN COMMUNICATION SYSTEM(w/ Toyota Safety Sense) Check Bus 3 Line for Short to GND

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminal 6 (CA3H) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3, or terminal 21 (CA3L) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3.

Symptom Trouble Area
No resistance exists between terminal 6 (CA3H) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3, or terminal 21 (CA3L) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3.

  • Short to ground in CAN main bus line

  • Short to ground in CAN branch line

  • Central gateway ECU (network gateway ECU)

  • Radio and display receiver assembly*1

  • CAN junction connector LH

WIRING DIAGRAM

A004FOKE02

CAUTION / NOTICE / HINT

Note


  • 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, switches or opening or closing the doors. After that, disconnect the cable from the negative (-) auxiliary 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 (-) 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.

  • 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.

  • After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.

  • DTC check procedure: Turn the ignition switch to ON (IG), turn the cruise control system on using the cruise control main switch (ON/OFF switch), wait at least 60 seconds, and then drive the vehicle at a speed of 20 km/h (12 mph) or more.

  • After the repair, perform Communication Bus Check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal Click here.

Tech Tips


  • Operating the ignition switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.

  • Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

  • Connectors that connect to the CAN junction connector can be distinguished by color of their CAN bus lines. When the connectors have been disconnected from the CAN junction connector, reconnecting the connectors to non-original positions on the CAN junction connector does not affect system performance. However, it is preferred to reconnect the connectors to their original positions to avoid negative effects on the wiring such as tension on the wiring harnesses, and to make future maintenance easier.

PROCEDURE


  1. CHECK FOR SHORT TO GND IN CAN BUS LINE (CAN J/C LH)


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

    2. Disconnect the CAN junction connector LH.

    3. A004G76E02
      Text in Illustration
      *1 DLC3
      *a

      Front view of wire harness connector

      (to CAN Junction Connector LH)
      *b Central Gateway ECU (Network Gateway ECU) (CA3H and CA3L Terminal)
      *c Central Gateway ECU (Network Gateway ECU) (CAYH and CAYL Terminal)
      *d to Radio and Display Receiver Assembly (w/ Display)

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

      Standard Resistance
      Tester Connection Condition Specified Condition Connected to
      F90-5 (CANH) - F3-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Radio and display receiver assembly*1
      F90-16 (CANL) - F3-4 (CG)
      F90-6 (CANH) - F3-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Central gateway ECU (network gateway ECU) (CAYH and CAYL terminal)
      F90-17 (CANL) - F3-4 (CG)
      F90-7 (CANH) - F3-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Central gateway ECU (network gateway ECU) (CA3H and CA3L terminal)
      F90-18 (CANL) - F3-4 (CG)

      • *: w/ Display

      Result
      Result Proceed to
      OK A
      NG (ECU or sensor bus line) B

    A

    REPLACE CAN JUNCTION CONNECTOR LH

    B

  2. CHECK FOR SHORT TO GND IN CAN BUS LINE (ECU, SENSOR)


    1. Reconnect all wire harness connectors (CAN junction connector LH).

    2. Disconnect the ECU or sensor connected to the CAN bus line that is shorted to ground.

      Tech Tips

      If the ECU or sensor has multiple connectors, disconnect the connector that includes the CAN bus lines. To determine the ECU or sensor that is connected to the shorted bus line, refer to the terminals of ECU tables Click here.

    3. A004FNRE01
      Text in Illustration
      *1 DLC3
      *a

      Component with harness connected

      (Central Gateway ECU (Network Gateway ECU))

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      F89-6 (CA3H) - F3-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      F89-21 (CA3L) - F3-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher

      Tech Tips

      If the resistance changes to 200 Ω or higher when the connector is disconnected from the ECU (or sensor), there may be a short in the ECU (or sensor).


    OK

    REPLACE CORRESPONDING ECU OR SENSOR

    NG

    REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BUS LINE OR CONNECTOR