Last Modified: 09-10-2025 6.11:8.1.0 Doc ID: RM100000001AU75
Model Year Start: 2019 Model: Avalon Prod Date Range: [04/2018 -           ]
Title: SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: C1781; Suspension Control ECU Malfunction; 2019 - 2022 MY Avalon Avalon HV [04/2018 -        ]

DTC

C1781

Suspension Control ECU Malfunction

DESCRIPTION

If a malfunction in the absorber control ECU is detected, DTC C1781 is stored.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Warning Indicate

Memory

C1781

Suspension Control ECU Malfunction

One of the following conditions is met:

  • A nonvolatile memory write or read error occurs.
  • A CAN communication register is stuck.
  • An overheat protection function malfunction occurs.
  • Absorber control ECU
  • CAN communication system

Does not come on

Yes

CAUTION / NOTICE / HINT

NOTICE:

  • Before performing troubleshooting, inspect the connectors of related circuits.
  • If DTC C1782 (Power Source Voltage Malfunction) is output at the same time, perform troubleshooting for C1782 first.

    Click here 2019 - 2022 MY Avalon Avalon HV [04/2018 -        ]; SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: C1782; Low Battery Positive Voltage

  • Before replacing the absorber control ECU, perform all of the following:
    • Symptom simulation.

      Click here 2019 - 2022 MY Avalon Avalon HV [04/2018 -        ]; INTRODUCTION: HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS: HOW TO PROCEED WITH TROUBLESHOOTING

    • DTC inspection.

      Click here 2019 - 2022 MY Avalon Avalon HV [04/2018 -        ]; SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: DTC CHECK / CLEAR

    • Techstream inspection.

      Click here 2019 MY Avalon HV Avalon [04/2018 - 08/2019]; SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: DATA LIST / ACTIVE TEST 2020 - 2022 MY Avalon Avalon HV [08/2019 -        ]; SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: DATA LIST / ACTIVE TEST

      • If no malfunctions are found in other areas, replace the absorber control ECU.
  • After replacing the absorber control ECU with a new one, perform registration of vehicle identification information.

    Click here 2019 - 2022 MY Avalon Avalon HV [04/2018 -        ]; SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: TEST MODE PROCEDURE

PROCEDURE

PROCEDURE

1.

CHECK FOR DTCS (CAN COMMUNICATION SYSTEM)

(a) Check for DTCs.

Click here 2019 - 2022 MY Avalon Avalon HV [04/2018 -        ]; SUSPENSION CONTROL: ADAPTIVE VARIABLE SUSPENSION SYSTEM: DTC CHECK / CLEAR

Chassis > Air suspension > Trouble Codes

Result

Proceed to

CAN DTCs are not output

A

CAN DTCs are output

B
A

REPLACE ABSORBER CONTROL ECU

Click here 2019 - 2021 MY Avalon Avalon HV [04/2018 - 08/2021]; SUSPENSION CONTROL: SUSPENSION CONTROL ECU: REMOVAL 2022 MY Avalon Avalon HV [08/2021 -        ]; SUSPENSION CONTROL: SUSPENSION CONTROL ECU: REMOVAL

B

GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)