Inspection Procedure 26: A/C Switch System

OPERATION

The battery voltage is applied to the engine-A/T-ECU (terminal No. 83) from the A/C-ECU (terminal No. 4).

FUNCTION

When the A/C switch is in "ON" position, A/C switch ON signal is inputted to the engine-A/T-ECU from the A/C-ECU. In response to the signal, the engine-A/T-ECU controls the A/C compressor relay.

PROBABLE CAUSE

Failed A/C

Failed A/C system

Open/short circuit in A/C circuit or loose connector contact

Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at C-112 engine-A/T-ECU connector.

Measure engine-A/T-ECU terminal voltage.

Engine: Idling

A/C set temperature:

Maximum Cool when temperature in cabin is 25°C or more

Maximum Hot when temperature in cabin is 25°C or less

Voltage between terminal No. 83 and earth.

OK:

System voltage (when A/C is ON)

0.5 V or less (when A/C is OFF)

Q: Is the check result normal?

YES: Go to Step 6

.
NO: Go to Step 2

STEP 2. Perform voltage measurement at C-06 A/C-ECU connector.

Measure engine-A/T-ECU terminal voltage.

Engine: Idling

A/C set temperature:

Maximum Cool when temperature in cabin is 25°C or more

Maximum Hot when temperature in cabin is 25°C or less

Voltage between terminal No. 4 and earth.

OK: System voltage

Q: Is the check result normal?

YES: Go to Step 5

.
NO: Go to Step 3

STEP 3. Connector check: C-06 A/C-ECU connector and C-110 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 4

.
NO: Repair.

STEP 4. Check harness between C-06 A/C-ECU connector and C-110 (terminal No. 83) engine-A/T-ECU connector.

NOTE: Before checking harness, check intermediate connector C-104, and repair if necessary.

Check output line for short circuit.

Q: Is the check result normal?

YES: Check A/C system (Refer to GROUP 55A - Troubleshooting

).
NO: Repair.

STEP 5. Connector check: C-06 A/C-ECU connector and C-110 engine-A/T-ECU connector

Q: Is the check result normal?

YES:

Check intermediate connector C-104, and repair if necessary. If intermediate connector is normal, check and repair harness between C-06 (terminal No. 4) A/C-ECU connector and C-110 (terminal No. 83) engine-A/T-ECU connector.

Check output line for open circuit.

NO: Repair.

STEP 6. Connector check: C-110 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 7

.
NO: Repair.

STEP 7. MUT-II/III Data List

Item 28: A/C switch

Engine: Idling

A/C set temperature:

Maximum Cool when temperature in cabin is 25°C or more

Maximum Hot when temperature in cabin is 25°C or less

OK:

ON (when A/C is ON)

OFF (when A/C is OFF)

Q: Is the check result normal?

YES: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points

).
NO: Replace engine-A/T-ECU.


Inspection Procedure 26: A/C Switch System

OPERATION The battery voltage is applied to the engine-A/T-ECU (terminal No. 83) from the A/C-ECU (terminal No. 4).
FUNCTION When the A/C switch is in "ON" position, A/C switch ON signal is inputted to the engine-A/T-ECU from the A/C-ECU. In response to the signal, the engine-A/T-ECU controls the A/C compressor relay.
PROBABLE CAUSE Failed A/C Failed A/C system Open/short circuit in A/C circuit or loose connector contact Failed engine-A/T-ECU
	DIAGNOSIS PROCEDURE

	STEP 1. Perform voltage measurement at C-112 engine-A/T-ECU connector.
	Measure engine-A/T-ECU terminal voltage. Engine: Idling A/C set temperature: Maximum Cool when temperature in cabin is 25°C or more Maximum Hot when temperature in cabin is 25°C or less Voltage between terminal No. 83 and earth. OK: System voltage (when A/C is ON) 0.5 V or less (when A/C is OFF) Q: Is the check result normal? YES: Go to Step 6 . NO: Go to Step 2 .
	STEP 2. Perform voltage measurement at C-06 A/C-ECU connector.
	Measure engine-A/T-ECU terminal voltage. Engine: Idling A/C set temperature: Maximum Cool when temperature in cabin is 25°C or more Maximum Hot when temperature in cabin is 25°C or less Voltage between terminal No. 4 and earth. OK: System voltage Q: Is the check result normal? YES: Go to Step 5 . NO: Go to Step 3 .
	STEP 3. Connector check: C-06 A/C-ECU connector and C-110 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 4 . NO: Repair.
	STEP 4. Check harness between C-06 A/C-ECU connector and C-110 (terminal No. 83) engine-A/T-ECU connector.
	NOTE: Before checking harness, check intermediate connector C-104, and repair if necessary. Check output line for short circuit. Q: Is the check result normal? YES: Check A/C system (Refer to GROUP 55A - Troubleshooting ). NO: Repair.
	STEP 5. Connector check: C-06 A/C-ECU connector and C-110 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Check intermediate connector C-104, and repair if necessary. If intermediate connector is normal, check and repair harness between C-06 (terminal No. 4) A/C-ECU connector and C-110 (terminal No. 83) engine-A/T-ECU connector. Check output line for open circuit. NO: Repair.
	STEP 6. Connector check: C-110 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 7 . NO: Repair.
	STEP 7. MUT-II/III Data List Item 28: A/C switch Engine: Idling A/C set temperature: Maximum Cool when temperature in cabin is 25°C or more Maximum Hot when temperature in cabin is 25°C or less OK: ON (when A/C is ON) OFF (when A/C is OFF) Q: Is the check result normal? YES: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ). NO: Replace engine-A/T-ECU.