Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Lost Communication with "Seat Control Module A" (U0208)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Power Source & Network / Networking / Can Communication System / 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 switch assembly LH continues.
  • Position control ECU and switch assembly LH branch line or connector
  • Power source circuit of position control ECU and switch assembly LH
  • Position control ECU and switch assembly LH ground circuit
  • Position control ECU and switch assembly LH

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 U0208 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.

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  • 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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  • 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 20 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.

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  • 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 (POSITION CONTROL ECU AND SWITCH ASSEMBLY LH BRANCH LINE)

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

(b) Disconnect the c6 position control ECU and switch assembly LH connector.

*a

Front view of wire harness connector

(to Position Control ECU and Switch Assembly LH)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

c6-8 (CANP) - c6-7 (CANN)

Cable disconnected from negative (-) battery terminal

54 to 69 Ω
NG

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (POSITION CONTROL ECU AND SWITCH ASSEMBLY LH)
OK

3.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the c5 position control ECU and switch assembly LH connector.

*a

Front view of wire harness connector

(to Position Control ECU and Switch Assembly LH)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

c5-2 (GND) - Body ground

Cable disconnected from negative (-) battery terminal

Below 1 Ω

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

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

c5-7 (+B) - Body ground

Always

11 to 14 V

c6-3 (IG) - Body ground

Engine switch on (IG)

11 to 14 V

c6-12 (SYSB) - Body ground

Always

11 to 14 V

*a

Front view of wire harness connector

(to Position Control ECU and Switch Assembly LH)
OK

REPLACE POSITION CONTROL ECU AND SWITCH ASSEMBLY LH

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
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