Inspection Procedure 18: Poor heater performance <RHD 4M41 A/T>

CIRCUIT OPERATION

If heater performance is poor even under the following conditions, the communication circuit system between A/C-ECU and engine-ECU may be defective.

Air outlet: FOOT/DEF, FOOT, FACE/FOOT
Temperature control dial: 29°C (MAX HOT)
Coolant temperature: 80 degrees Celsius or less

note

When the coolant temperature becomes above 80 degrees Celsius and PTC heater stops the operation, the PTC heater does not operate until coolant temperature becomes below 75 degrees Celsius.

PROBABLE CAUSES

Malfunction of the A/C-ECU
Malfunction of the engine-ECU
Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. Connector checks: D-08 A/C-ECU connector, D-213 engine-ECU connector

Q. Is the check result normal?

	Go to Step 2.

	Repair the connector.

STEP 2. Check the wiring harness between D-08 A/C-ECU connector terminal No.14 and D-213 engine-ECU connector terminal No.6.

note

Prior to the wiring harness inspection, check intermediate connector D-230, and repair if necessary.

Check the engine-ECU input line for open circuit.

Q. Is the check result normal?

	Go to Step 3.

	Repair the wiring harness.

STEP 3. Replace the A/C-ECU and recheck the trouble symptom

Q. Is the check result normal?

	The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

	Replace the engine-ECU.