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Inspection Procedure 5: The PTC heater does not work
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
When the PTC heater does not work under the following conditions, the PTC heater circuit system may be defective.
PTC heater operating conditions
  • Engine coolant temperature: 75°C (167°F) or less
  • Ambient air temperature: 15°C (59°F) or less
  • The rate of operation of the generator, which is transmitted over the CAN, is 70% or less
 
 
 
PROBABLE CAUSES
  • Malfunction of the PTC heater
  • Malfunction of the PTC heater relay
  • Malfunction of the heater control unit (PTC-ECU)
  • Damaged the wiring harness or connectors
 
 
 
 
DIAGNOSIS
STEP 1. Check the PTC heater relay 1 and 2.
Refer to .
Is the check result normal?
Go to Step 2.
Replace the PTC heater relay.
 
STEP 2. Measure the voltage at the PTC heater relay connectors (1 and 2).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Ignition switch: "ON"
(3) Voltage between terminal No. 4 of each PTC heater relay and body ground.
OK: Battery voltage
Is the check result normal?
Go to Step 4.
Go to Step 3.
 
STEP 3. Check the wiring harness wires between terminal No. 4 of each PTC heater relay connector (1 and 2) and fusible link (7) for open or short circuit.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 4. Measure the resistance at the PTC heater relay connectors (1 and 2).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Resistance between terminal No. 3 of each PTC heater relay and body ground.
OK: Continuity exists (2 Ω or less).
Is the check result normal?
Go to Step 5.
Go to Step 7.
 
STEP 5. Check the wiring harness wires between each PTC heater relay connector (1 and 2) and body ground for open or short circuit.
noteBefore the wiring harness check, check the junction block connector, and repair if necessary.
Is the check result normal?
Go to Step 6.
Repair the connector(s) or wiring harness.
 
STEP 6. Check the wiring harness wires between each PTC heater relay connector (1 and 2) and the heater control unit (PTC-ECU) terminals E and COME for open or short circuit.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 7. Measure the voltage at the PTC heater relay connectors (1 and 2).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Ignition switch: "ON"
(3) Voltage between terminal No. 1 of each PTC heater relay and body ground.
OK: Battery voltage
Is the check result normal?
Go to Step 9.
Go to Step 8.
 
STEP 8. Check the wiring harness wires between each PTC heater relay connector (1 and 2) and the PTC heater control unit (PTC-ECU) connector terminals HTR1 and HTR2 for open or short circuit.
Is the check result normal?
Intermittent malfunction. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunctions .)
Repair the wiring harness.
 
STEP 9. Measure the resistance at the PTC heater relay connectors (1 and 2).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Resistance between terminal No. 2 and body ground.
OK: Continuity exists (2 Ω or less).
Is the check result normal?
Intermittent malfunction. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunctions .)
Go to Step 10.
 
STEP 10. Check the wiring harness wires between each PTC heater relay connector (1 and 2) and body ground for open or short circuit.
noteBefore the wiring harness check, check the PTC heater connectors, and then repair if necessary.
Is the check result normal?
Replace the PTC heater.
Repair the wiring harness.