Last Modified: 06-05-2026 6.11:8.1.0 Doc ID: RM0000003TPJ55T
Model Year Start: 2026 Model: GR Corolla Prod Date Range: [03/2026 -           ]
Title: HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM (for Gasoline Model with Automatic Air Conditioning System): B142A88; Servo Motor LIN Communication Bus off; 2026 MY GR Corolla Corolla Corolla Hatchback [03/2026 -        ]

DTC

B142A88

Servo Motor LIN Communication Bus off

DESCRIPTION

The air conditioning harness assembly connects the air conditioning amplifier assembly and the servo motors.

The air conditioning amplifier assembly supplies power and sends operation instructions to each servo motor through the air conditioning harness assembly.

Each servo motor sends damper position information to the air conditioning amplifier assembly.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

B142A88

Servo Motor LIN Communication Bus off

Diagnosis Condition:

  • Ignition switch ON

Malfunction:

  • Error or open in communication line between air conditioning amplifier assembly and each servo motor

Detection Time:

  • Continuously for 10 seconds or more
  • Air conditioning harness assembly
  • No. 1 air conditioning radiator damper servo sub-assembly
  • Air conditioning amplifier assembly

Memorized

DTC Detection Condition Combination Table

 

Vehicle Condition

Pattern 1

Pattern 2

Diagnosis Condition

Ignition switch ON

○

○

Malfunction

Error in communication line between air conditioning amplifier assembly and each servo motor

○

-

Open in communication line between air conditioning amplifier assembly and each servo motor

-

○

Detection Time

Continuously for 10 seconds or more

Continuously for 10 seconds or more

Trip Count

1 trip

1 trip

HINT:

If the conditions of either of these patterns are detected, a DTC will be stored.

WIRING DIAGRAM

except TMUK Made:
for TMUK Made:

PROCEDURE

1.

PERFORM ACTIVE TEST USING GTS

(a) Perform the Active Test according to the display on the GTS.

Body Electrical > Air Conditioner > Active Test

Tester Display

Measurement Item

Control Range

Diagnostic Note

Front Left Air Mix Damper Control Servo Motor

This test activates the front left air mix damper control servo motor.

(No. 1 air conditioning radiator damper servo sub-assembly (front left side air mix))

128: Min

384: Max
  • Operates between 165 to 257
  • *2

Front Right Air Mix Damper Control Servo Motor

This test activates the front right air mix damper control servo motor.

(No. 1 air conditioning radiator damper servo sub-assembly (front right side air mix))

128: Min

384: Max
  • Operates between 255 to 347
  • *2

Air Inlet Damper Control Servo Motor

This test activates the air inlet damper control servo motor.

(No. 1 blower damper servo sub-assembly*3 or No. 5 air conditioning radiator damper servo sub-assembly*4)

128: Min

384: Max

Operates between 220 to 256

Front Air Mix Damper Control Servo Motor

This test activates the front air mix damper control servo motor.

(No. 1 air conditioning radiator damper servo sub-assembly (air mix))

128: Min

384: Max
  • Operates between 165 to 257
  • *1

Front Air Outlet Damper Control Servo Motor

This test activates the front air outlet damper control servo motor.

(No. 1 air conditioning radiator damper servo sub-assembly (front mode))

128: Min

384: Max

Operates between 256 to 348
  • *1: for Single Type
  • *2: for Dual Type
  • *3: for M20A-FKS
  • *4: for G16E-GTS

Body Electrical > Air Conditioner > Active Test

Body Electrical > Air Conditioner > Active Test

Body Electrical > Air Conditioner > Active Test

Body Electrical > Air Conditioner > Active Test

Body Electrical > Air Conditioner > Active Test

Result

Result

Proceed to

All of the damper servo motors do not operate

A

Any of the damper servo motors does not operate

B

All of the damper servo motors operate

C
B

REPLACE AIR CONDITIONING HARNESS ASSEMBLY

C

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

A

2.

CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY

NOTICE:

When inspecting the air conditioning amplifier assembly, be careful not to cause a short.

(a) except TMUK Made

(1) Disconnect the m3 air conditioning amplifier assembly connector.

*a

Component without harness connected

(Air Conditioning Amplifier Assembly)

-

-

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

Standard Resistance

Tester Connection

Condition

Specified Condition

m3-2 (BUSG) - Body ground

Always

Below 1 Ω

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

Standard Voltage

Tester Connection

Condition

Specified Condition

m3-4 (BUSB) - m3-2 (BUSG)

Ignition switch off

11 to 14 V

(4) Using an oscilloscope, check the waveform.

Item

Content

Tester Connection

m3-3 (BUS) - m3-2 (BUSG)

Tool Setting

2 V/DIV., 20 μs/DIV.

Condition

Ignition switch ON

OK:

The waveform displays properly.

(b) for TMUK Made

(1) Disconnect the m6 air conditioning amplifier assembly connector.

*a

Component without harness connected

(Air Conditioning Amplifier Assembly)

-

-

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

Standard Resistance

Tester Connection

Condition

Specified Condition

m6-2 (BUSG) - Body ground

Always

Below 1 Ω

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

Standard Voltage

Tester Connection

Condition

Specified Condition

m6-4 (BUSB) - m6-2 (BUSG)

Ignition switch off

11 to 14 V

(4) Using an oscilloscope, check the waveform.

Item

Content

Tester Connection

m6-3 (BUS) - m6-2 (BUSG)

Tool Setting

2 V/DIV., 20 μs/DIV.

Condition

Ignition switch ON

OK:

The waveform displays properly.

OK

REPLACE AIR CONDITIONING HARNESS ASSEMBLY

NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY