Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: Lost Communication with "Door Control Module A" (U0199)

Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual / Power Source & Network / Networking / Can Communication System / Lost Communication with "Door Control Module A" (U0199)

DESCRIPTION

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

U0199

Lost Communication with "Door Control Module A"

No communication from the outer mirror control ECU assembly (for front passenger side) continues.
  • Outer mirror control ECU assembly (for front passenger side) branch line or connector
  • Power source circuit of outer mirror control ECU assembly (for front passenger side)
  • Outer mirror control ECU assembly (for front passenger side) ground circuit
  • Outer mirror control ECU assembly (for front passenger side)

HINT:

The main body ECU (multiplex network body ECU) stores DTCs when it detects a communication stop or network communication error for ECUs connected to sub bus 1.

HINT:

This diagnostic procedure is for when DTC U0199 is output by the main body ECU (multiplex network body ECU) (Techstream display: Main Body).

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • 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.

    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 engine switch on (IG) and wait for at least 21 seconds.
  • After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed.

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

HINT:

  • Operating the engine 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.

PROCEDURE

1.

RECONFIRM DTC OUTPUT

(a) Reconfirm DTCs.

HINT:

If DTC U1002 is output from Main Body of the main body ECU (multiplex network body ECU), this indicates a sub bus 1 malfunction. Troubleshoot for DTC U1002 and check for malfunctions in sub bus 1.

Body Electrical > Main Body > Trouble Codes

Result

Proceed to

DTC U1002 is not output from the main body ECU (multiplex network body ECU) (Techstream display: Main Body)

A

DTC U1002 is output from the main body ECU (multiplex network body ECU) (Techstream display: Main Body)

B
B

GO TO DIAGNOSTIC PROCEDURE INDICATED BY OUTPUT DTC

A

2.

CHECK FOR OPEN IN SUB BUS 1 LINES (OUTER MIRROR CONTROL ECU ASSEMBLY (FOR FRONT PASSENGER SIDE) BRANCH LINE)

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

(b) Disconnect the M4 outer mirror control ECU assembly (for front passenger side) connector.

*a

Front view of wire harness connector

(to Outer Mirror Control ECU Assembly (for Front Passenger Side))

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

M4-9 (CANP) - M4-8 (CANN)

Cable disconnected from negative (-) battery terminal

54 to 69 Ω
NG

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (OUTER MIRROR CONTROL ECU ASSEMBLY (FOR FRONT PASSENGER SIDE))
OK

3.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

M4-7 (GND) - Body ground

Cable disconnected from negative (-) battery terminal

Below 1 Ω

*a

Front view of wire harness connector

(to Outer Mirror Control ECU Assembly (for Front Passenger Side))

(b) Reconnect the cable to the negative (-) battery terminal.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

M4-5 (SIG) - Body ground

Engine switch on (IG)

11 to 14 V

M4-6 (CPUB) - Body ground

Always

11 to 14 V

M4-14 (BDR) - Body ground

Always

11 to 14 V

*a

Front view of wire harness connector

(to Outer Mirror Control ECU Assembly (for Front Passenger Side))
OK

REPLACE OUTER MIRROR CONTROL ECU ASSEMBLY (FOR FRONT PASSENGER SIDE)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
    Terminals Of Ecu
    TERMINALS OF ECU NOTICE: 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 di ...

    Lost Communication with "Seat Control Module A" (U0208)
    DESCRIPTION DTC No. Detection Item DTC Detection Condition Trouble Area Note U0208 Lost Communication with "Seat Control Module A" No communication from the position control ECU and ...

    Other materials:

    Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Power Mirror Control System (w/ Memory): Dtc Check / Clear
    DTC CHECK / CLEAR CHECK DTC (a) Connect the Techstream to the DLC3. (b) Turn the engine switch on (IG). (c) Turn the Techstream on. (d) Enter the following menus: Body Electrical / Mirror L or Mirror R / Trouble Codes. Body Electrical > Mirror L > Trouble Codes Body Electrical > Mirror R &g ...

    Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Power Mirror Control System (w/o Memory): System Diagram
    SYSTEM DIAGRAM Communication Table Sender Receiver Signal Line Air Conditioning Amplifier Assembly Main Body ECU (Multiplex Network Body ECU) Mirror heater drive request signal CAN Main Body ECU (Multiplex Network Body ECU) Outer Mirror Control ECU Assembly IG sign ...

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

    © 2026 Copyright www.lexusrx.net
    0.0142