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Diagnosis Item 45: Diagnose when the scan tool cannot receive the data sent by electric heater-ECU.
 
 
cautionWhen servicing a CAN bus line, ground yourself by touching a metal object such as an unpainted water pipe. If you fail to do, a component connected to the CAN bus line may be broken.
 
 
FUNCTION
The diagnostic result demonstrates that "the scan tool (M.U.T.-IIISE) cannot receive the sent data from the electric heater-ECU" when the scan tool (M.U.T.-IIISE) checks the periodically sent data from each ECU and cannot receive the electric heater-ECU data only.
 
 
TROUBLE JUDGMENT CONDITIONS
Scan tool (M.U.T.-IIISE) judges the trouble when the periodically sent data from electric heater-ECU cannot be received.
 
 
PROBABLE CAUSES
  • Damaged harness wires and connectors
  • Power supply circuit malfunction of the electric heater-ECU
  • Malfunction of the electric heater (electric heater-ECU)
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Connector check: joint connector (CAN9) and electric heater connector.
cautionThe strand end of the twist wire should be within 10 cm (4 inches) from the connector. For details refer to .
When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.
Is the check result normal?
Go to Step 2.
Repair the defective connector. Replace the joint connector as necessary.
 
STEP 2. Resistance measurement at joint connector (CAN9) and electric heater connector.
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN9) and the electric heater connector, and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Continuity between joint connector (CAN9) terminal No.8 and electric heater connector terminal No.3
OK: Continuity (2 ohms or less)
(5) Continuity between joint connector (CAN9) terminal No.6 and electric heater connector terminal No.4
OK: Continuity (2 ohms or less)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<All the resistances measure 2 ohms or less> Go to Step 3.
: <Either or all of the resistances measure more than 2 ohms> Repair the wiring harness between joint connector (CAN9) and the electric heater connector.
 
STEP 3. Resistance measurement at electric heater connector.
dangerCarry out the check on the high-voltage circuit while reading carefully the precautions on handling a high-voltage vehicle. Refer to GROUP 00 - Precautions on how to use the high-voltage vehicle .
dangerWear the specified protection equipment during the check.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the electric heater, and measure at the equipment side.
(2) Resistance between electric heater connector terminal Nos.3 and 4
OK: 1 kΩ or more
Is the check result normal?
Power supply to the electric heater may be suspected. Diagnose the electric heater-ECU. Refer to GROUP 55 - Troubleshooting .
Replace the electric heater (electric heater-ECU).