Inspection Procedure 28: A/C Load Signal System

OPERATION

The A/C load signal is inputted to the engine-A/T-ECU (terminal No. 78) from the A/C-ECU (terminal No. 5). <Manual A/C> or (terminal No. 32) <Auto A/C>

FUNCTION

The magnitude of the A/C compressor load is detected and input to the engine-A/T-ECU. The engine-A/T-ECU provides A/C idle up control according to the A/C compressor load condition.

PROBABLE CAUSE

Failed A/C-ECU

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

Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at C-136 engine-A/T-ECU.

Measure engine-A/T-ECU terminal voltage.

Engine: Idling

A/C switch: ON (A/C compressor in driven state)

Voltage between terminal No. 78 and earth

OK:

1 V or less (when the temperate around the atmospheric air temperature sensor is 18°C or more, and the A/C is set to the lowest temperature and the maximum air flow rate)

System voltage (when the A/C is set to the temperature in the cabin and the minimum air flow rate)

Q: Is the check result normal?

YES: Go to Step 2

.
NO: Go to Step 4

STEP 2. Connector check: C-136 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 3

.
NO: Repair.

STEP 3. Check the trouble symptoms.

Q: Does trouble symptom persist?

YES: Replace engine-A/T-ECU.
NO: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points

STEP 4. Connector check: C-136 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 5

.
NO: Repair.

STEP 5. Perform voltage measurement at C-06 A/C-ECU <Manual A/C> connector or C-26 A/C-ECU <Auto A/C> connector.

Measure A/C-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. 5 and earth <Manual A/C>

Voltage between terminal No. 32 and earth <Auto A/C>

OK: System voltage

Q: Is the check result normal?

YES: Go to Step 8

.
NO: Go to Step 6

STEP 6. Connector Check: C-06 A/C-ECU <Manual A/C> connector or C-26 A/C-ECU <Auto A/C> connector

Q: Is the check result normal?

YES: Go to Step 7

.
NO: Repair.

STEP 7. Check harness between C-06 (terminal No. 5) or C-26 (terminal No. 32) A/C-ECU connector and C-136 (terminal No. 78) 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 - Check Chart for Trouble Symptoms

).
NO: Repair.

STEP 8. Check connector: C-06 A/C-ECU connector <Manual A/C> or C-26 A/C-ECU connector <Auto A/C>

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. 5) or C-26 (terminal No. 32) A/C-ECU connector and C-136 (terminal No. 78) engine-A/T-ECU connector.

Check output line for open circuit.

NO: Repair.


Inspection Procedure 28: A/C Load Signal System

OPERATION The A/C load signal is inputted to the engine-A/T-ECU (terminal No. 78) from the A/C-ECU (terminal No. 5). <Manual A/C> or (terminal No. 32) <Auto A/C>
FUNCTION The magnitude of the A/C compressor load is detected and input to the engine-A/T-ECU. The engine-A/T-ECU provides A/C idle up control according to the A/C compressor load condition.
PROBABLE CAUSE Failed A/C-ECU Open/short circuit in A/C load signal circuit or loose connector contact Failed engine-A/T-ECU
	DIAGNOSIS PROCEDURE

	STEP 1. Perform voltage measurement at C-136 engine-A/T-ECU.
	Measure engine-A/T-ECU terminal voltage. Engine: Idling A/C switch: ON (A/C compressor in driven state) Voltage between terminal No. 78 and earth OK: 1 V or less (when the temperate around the atmospheric air temperature sensor is 18°C or more, and the A/C is set to the lowest temperature and the maximum air flow rate) System voltage (when the A/C is set to the temperature in the cabin and the minimum air flow rate) Q: Is the check result normal? YES: Go to Step 2 . NO: Go to Step 4 .
	STEP 2. Connector check: C-136 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 3 . NO: Repair.
	STEP 3. Check the trouble symptoms. Q: Does trouble symptom persist? YES: Replace engine-A/T-ECU. NO: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).
	STEP 4. Connector check: C-136 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 5 . NO: Repair.
	STEP 5. Perform voltage measurement at C-06 A/C-ECU <Manual A/C> connector or C-26 A/C-ECU <Auto A/C> connector.
	Measure A/C-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. 5 and earth <Manual A/C> Voltage between terminal No. 32 and earth <Auto A/C> OK: System voltage Q: Is the check result normal? YES: Go to Step 8 . NO: Go to Step 6 .
	STEP 6. Connector Check: C-06 A/C-ECU <Manual A/C> connector or C-26 A/C-ECU <Auto A/C> connector
	Q: Is the check result normal? YES: Go to Step 7 . NO: Repair.
	STEP 7. Check harness between C-06 (terminal No. 5) or C-26 (terminal No. 32) A/C-ECU connector and C-136 (terminal No. 78) 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 - Check Chart for Trouble Symptoms ). NO: Repair.
	STEP 8. Check connector: C-06 A/C-ECU connector <Manual A/C> or C-26 A/C-ECU connector <Auto A/C>
	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. 5) or C-26 (terminal No. 32) A/C-ECU connector and C-136 (terminal No. 78) engine-A/T-ECU connector. Check output line for open circuit. NO: Repair.