Toyota Yaris: Air Conditioning System / Servo Motor LIN Communication Bus off (B142A88)

Toyota Yaris XP210 (2020-2025) Reapir and Service Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System / Servo Motor LIN Communication Bus off (B142A88)

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 Status: Error or lost communication with 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 No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

B142A88

Servo Motor LIN Communication Bus off

Diagnosis Condition:

Ignition switch ON

Malfunction Status:

Error or lost communication with 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 communication with each servo motor	○	-
Malfunction	Lost communication with 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

CAUTION / NOTICE / HINT

NOTICE:

This DTC is also output when servomotor initialization has failed. When servomotor initialization has failed, repair any malfunctions and perform servomotor initialization again.

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PROCEDURE

1.	INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY

NOTICE:

When inspecting the air conditioning amplifier assembly, do not bring the tester probes too close to each other as a short circuit may occur.

(a) Disconnect the air conditioning amplifier assembly connector.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
h6-4 (BUSB) - Body ground	Always	11 to 14 V

Standard Resistance:

Tester Connection	Condition	Specified Condition
h6-2 (BUSG) - Body ground	Always	Below 1 Ω

*a	Component with harness connected (Air Conditioning Amplifier Assembly)

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

2.	INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY

*a	Component with harness connected (Air Conditioning Amplifier Assembly)

(a) Using an oscilloscope, check the waveform.

Item	Content
Terminal No.	h6-3 (BUS) ←→ h6-2 (BUSG)
Tool Setting	2 V/DIV., 2 ms./DIV.
Condition	Ignition switch ON

OK:

Waveform is similar to that shown in the illustration.

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

3.	INSPECT AIR CONDITIONING HARNESS ASSEMBLY

(a) Disconnect the h7 No. 1 air conditioning radiator damper servo sub-assembly connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
h6-2 (BUSG) - h7-6 (GND)	Always	Below 1 Ω
h6-3 (BUS) - h7-7 (LIN)	Always	Below 1 Ω
h6-4 (BUSB) - h7-8 (+B)	Always	Below 1 Ω

REPLACE NO. 1 AIR CONDITIONING RADIATOR DAMPER SERVO SUB-ASSEMBLY

REPLACE AIR CONDITIONING HARNESS ASSEMBLY

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