CAN Communication System (Diagnostic Codes (U1002 - U1121) & Circuit Tests): Overview Lexus GS IV

DESCRIPTION

1. The main body ECU (multiplex network body ECU) will store this DTC when no signals can be received from the ECUs that have been memorized as those that are connected to sub bus 1.
2. When the main body ECU (multiplex network body ECU) receives a response signal from the ECUs connected to sub bus 1, the main body ECU (multiplex network body ECU) recognizes and memorizes that the ECU is connected to sub bus 1. Based on this memorized data, the main body ECU (multiplex network body ECU) monitors for malfunctions in the ECUs connected to sub bus 1 when communicating with those ECUs. If the main body ECU (multiplex network body ECU) cannot receive response signals from the ECUs that have been memorized as those connected to sub bus 1, the main body ECU (multiplex network body ECU) determines that a malfunction exists.

1. *1: w/ Power Trunk Lid System
2. *2: except Standard Seat Type
3. *3: for Standard Seat Type
4. *4: for Luxury Seat Type

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1. For vehicles with a pre-collision system.

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1. The power management control ECU will store this DTC when no signals can be received from the ECUs that have been memorized as those that are connected to sub bus 15.
2. When the power management control ECU receives a response signal from the ECUs connected to sub bus 15, the power management control ECU recognizes and memorizes that the ECU is connected to sub bus 15. Based on this memorized data, the power management control ECU monitors for malfunctions in the ECUs connected to sub bus 15 when communicating with those ECUs. If the power management control ECU cannot receive response signals from the ECUs that have been memorized as those connected to sub bus 15, the power management control ECU determines that a malfunction exists.

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1. For vehicles with a intuitive parking assist system.

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HINT

Because of the location of the lane recognition camera assembly, it is subject to high temperatures. If the lane recognition camera sensor assembly becomes too hot, the power source is shut down to protect the system. At that time CAN communication also stops. However, in order to inform the driving support ECU that CAN communication has not stopped because of a CAN communication error, on/off signals are periodically sent from the HITP terminal.

1. For vehicles with a lane-keeping assist system.

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1. For vehicles with a pre-collision system.

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There may be an open circuit one of the V Bus main lines and/or a DLC3 branch line when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is 70 ohms or higher.

This malfunction is not related to the lines of a CAN main bus branch or to ECUs or sensors connected a CAN main bus branch.

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There may be a short circuit between the V Bus main lines and/or CAN branch lines when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is below 54 ohms.

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There may be a short circuit between one of the CAN bus lines and +B when no resistance exists between terminals 6 (CANH) and 16 (BAT) or 14 (CANL) and 16 (BAT) of the DLC3.

There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminals 6 (CANH) and 4 (CG) or 14 (CANL) and 4 (CG) of the DLC3.

If an ECU or sensor is not displayed on the "CAN Bus Check" screen of the Techstream and some ECUs and sensors repeatedly appear and disappear from the screen when the CAN main bus lines are normal (there is no open, short, short to +B or short to GND in the main bus lines), there may be an open circuit in either of one pair of CAN branch lines.

HINT

If some ECUs and sensors repeatedly appear and disappear from the "CAN Bus Check" screen, communication between the normal ECUs (sensors) and the Techstream may be affected by the incomplete signals that are output from the ECU that has an open circuit in either of its CAN branch lines. In this case, the CAN branch lines for the ECUs and sensors that repeatedly appear and disappear from the screen are normal and the ECU that is not displayed on the screen may be the main cause of the problem (this ECU may have an open circuit in either of its CAN branch lines).

See also:
• DIAGNOSIS SYSTEM [03/2012 - ]
• REMOVAL [03/2012 - ]