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Home >> Lexus >> 2019 >> RX 450h Base >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Exterior Lights >> Lighting System (W/ Automatic Headlight Beam Level Control System) (Diagnostic Codes) (2 Of 2) & Circuit Tests) >> Lighting System (W/ Automatic Headlight Beam Level Control System) >> DTC U0242: Lost Communication With Headlamp Control Module "B" [08/2019 - ] >> Description
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DTC U0242: Lost Communication With Headlamp Control Module "B" [08/2019 - ]: Description

for Multiple Beam Headlight: 

  1. The No. 1 headlight ECU sub-assembly LH communicates with the No. 1 headlight ECU sub-assembly RH via CAN communication. If communication between the No. 1 headlight ECU sub-assembly LH and No. 1 headlight ECU sub-assembly RH stops, the No. 1 headlight ECU sub-assembly LH will store this DTC.

for Single Beam Headlight: 

  1. The No. 1 headlight ECU sub-assembly LH communicates with the No. 1 headlight ECU sub-assembly RH via LIN communication. If communication between the No. 1 headlight ECU sub-assembly LH and No. 1 headlight ECU sub-assembly RH stops, the No. 1 headlight ECU sub-assembly LH will store this DTC.
FOR MULTIPLE BEAM HEADLIGHT

DTC No. Detection Item DTC Detection Condition Trouble Area DTC Output from
U0242 Lost Communication With Headlamp Control Module "B" Detection condition: 
  1. The power switch is on (IG).

Malfunction status: 
  1. A communication malfunction with the No. 1 headlight ECU sub-assembly RH is detected

Malfunction duration: 
  1. 10 seconds or more
  • Harness or connector
  • No. 1 headlight ECU sub-assembly LH
  • No. 1 headlight ECU sub-assembly RH
 AFS
FOR SINGLE BEAM HEADLIGHT

DTC No. Detection Item DTC Detection Condition Trouble Area DTC Output from
U0242 Lost Communication With Headlamp Control Module "B" Detection condition: 
  1. The power switch is on (IG).

Malfunction status: 
  1. A communication malfunction with the No. 1 headlight ECU sub-assembly RH is detected

Malfunction duration: 
  1. 10 seconds or more
  • Harness or connector
  • No. 1 headlight ECU sub-assembly LH
  • No. 1 headlight ECU sub-assembly RH
 HL AutoLeveling
FOR MULTIPLE BEAM HEADLIGHT:

Pattern DTC output part name
(Display on Techstream)		 Suspected Area (Malfunction Status)
No. 1 Headlight ECU Sub-assembly LH
(AFS)
U0242
Pattern 1 ◦
  • Open in CAN communication line (No. 1 headlight ECU sub-assembly LH - No. 1 headlight ECU sub-assembly RH)
  • Open or short in No. 1 headlight ECU sub-assembly LH internal circuit
  • Open or short in No. 1 headlight ECU sub-assembly RH internal circuit

◦: DTC is output

FOR SINGLE BEAM HEADLIGHT:

Pattern DTC output part name
(Display on Techstream)		 Suspected Area (Malfunction Status)
No. 1 Headlight ECU Sub-assembly LH
(HL AutoLeveling)
U0242
Pattern 1 ◦
  • Open in LIN communication line (No. 1 headlight ECU sub-assembly LH - No. 1 headlight ECU sub-assembly RH)
  • Open or short in No. 1 headlight ECU sub-assembly LH internal circuit
  • Open or short in No. 1 headlight ECU sub-assembly RH internal circuit

◦: DTC is output

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