Inspection Procedure 17: 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: MAX HOT
  • Coolant temperature: 82 degrees Celsius or less
note When the coolant temperature becomes above 82 degrees Celsius and PTC heater stops the operation, the PTC heater does not operate until coolant temperature becomes below 72 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.

  • 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.