Inspection Procedure 25: Heater Switch (Warm Up Switch) System <Vehicle with PTC Heater>




OPERATION



  • The ON/OFF state of the PTC heater switch (warm up switch) is input into the engine-ECU.
  • When the PTC heater switch (warm up switch) is turned ON and the battery voltage is applied to the engine-ECU, also the engine coolant temperature is low, the engine-ECU increases the idle speed to approximately 1, 300 r/min to promote the engine warm-up.

PROBABLE CAUSES



  • Failed PTC heater switch (warm up switch)
  • Damaged harness (Open circuit between heater switch and engine-ECU, and open circuit between PTC heater switch and J/B)
  • Damaged connector (Engine-ECU connector, PTC heater switch connector)
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check PTC heater rail switch itself

  • Check PTC heater switch (warm up switch) itself (Refer to GROUP 55A - Heater switch (warm up switch) - Inspection ).

Q. Is the check result normal?
Go to Step 2 .
Replace the PTC heater switch (warm up switch).

STEP 2. Connector check: C-151 PTC heater switch (warm up switch) connector

Q. Is the check result normal?

Go to Step 3 .

Repair or replace.

STEP 3. Perform voltage measurement at C-151 PTC heater switch (warm up switch) connector.


  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 2 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 4 .

Check intermediate connector C-132, C-138 and C-137, and repair if necessary. If intermediate connector connectors are normal, check and repair harness between C-151 (terminal No. 2) PTC heater switch (warm up switch) connector and C-209 (terminal No. 6) J/B connector.

STEP 4. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 5 .

Repair or replace.

STEP 5. Perform voltage measurement at C-105 engine-ECU connector.


  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 14 and earth.
OK:
    System voltage (Heater switch: ON)
    0 V (Heater switch: OFF)

Q. Is the check result normal?

Go to Step 6 .

Check intermediate connector C-53, and repair if necessary. If intermediate connector is normal, check and repair harness between C-105 (terminal No. 14) engine-ECU connector and C-151 (terminal No. 1) PTC heater switch (warm up switch) connector.

STEP 6. Check the trouble symptoms.

Q. Does trouble symptom persist?
Replace the engine-ECU. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).