Diagnosis Item 21: Diagnose when the M.U.T.-III cannot receive the data sent by A/C-ECU <vehicles with A/C> or heater control unit <vehicles without A/C>


caution When servicing a CAN bus line, earth 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



TROUBLE JUDGEMENT CONDITIONS



TROUBLESHOOTING HINTS



  • Malfunction of the connector [joint connector (CAN1) or A/C-ECU connector <vehicles with A/C> or heater control unit connector <vehicles without A/C> improperly connected]
  • Malfunction of the wiring harness [open circuit between the A/C-ECU connector <vehicles with A/C> or heater control unit connector <vehicles without A/C> and the joint connector (CAN1), or power supply circuit to the A/C-ECU <vehicles with A/C> or heater control unit <vehicles without A/C>]
  • Malfunction of the A/C-ECU <vehicles with A/C> or heater control unit <vehicles without A/C>

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-04 joint connector (CAN1) and C-15 A/C-ECU connector <vehicles with A/C> or C-60 heater control unit connector <vehicles without A/C>
caution The strand end of the twist wire should be within 10 cm from the connector. For details refer to .

Q. Is the check result normal?
Go to Step 2.
Repair the defective connector.

STEP 2. Check the wiring harness between C-15 A/C-ECU connector <vehicles with A/C> or C-60 heater control unit connector <vehicles without A/C> and C-04 joint connector (CAN1)
caution Strictly observe the specified wiring harness repair procedure. For details refer to .
Disconnect A/C-ECU connector <vehicles with A/C> or heater control unit connector <vehicles without A/C> and joint connector (CAN1), and check the following wiring harness for open circuit
(1)The wiring harness between C-15 A/C-ECU connector <vehicles with A/C> or C-60 heater control unit connector <vehicles without A/C> terminal No.11 and C-04 joint connector (CAN1) terminal No.1 <LHD> or 2 <RHD> <CAN_H>
OK: Continuity exists (2 Ω or less)
(2)The wiring harness between C-15 A/C-ECU connector <vehicles with A/C> or C-60 heater control unit connector <vehicles without A/C> terminal No.12 and C-04 joint connector (CAN1) terminal No.12 <LHD> or 13 <RHD> <CAN_L>
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Check the power supply circuit of the A/C-ECU <vehicles with A/C> or heater control unit <vehicles without A/C>. Refer to GROUP 55A, Manual A/C and heater Diagnosis or GROUP 55B, Auto A/C Diagnosis .
Repair the wiring harness.