Diagnostic Item 19

DIAGNOSTIC ITEM 19: Diagnose When The Scan Tool Cannot Receive The Data Sent By A/C-ECU.

CAUTION: When servicing a CAN bus line, ground yourself by touching a metal object such as an unpainted water pipe. If you fail to do so, a component connected to the CAN bus line may be damaged.

CAN-B Communication Circuit (Part 1):

CAN-B Communication Circuit (Part 2):

FUNCTION
If the scan tool MB991958 cannot communicate with the A/C-ECU, this diagnosis result will be set.

TROUBLE JUDGEMENT CONDITIONS
If a communication flag is not set for the A/C-ECU, the ETACS-ECU determines that there is a failure.

TROUBLESHOOTING HINTS
- Malfunction of the connector [joint connector (CAN1), A/C-ECU connector improperly connected]
- Malfunction of the wiring harness [open circuit between the A/C-ECU connector and the joint connector (CAN1), power supply circuit to the A/C-ECU]
- Malfunction of the A/C-ECU

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check joint connector (CAN1) C-105 and A/C-ECU connector C-22 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

CAUTION: The strand end of the twisted wire should be within 10 cm (4 inches) from the connector.

Q : Are joint connector (CAN1) C-105 and A/C-ECU connector C-22 in good condition?

YES : Go to Step 2.

NO : Repair the damaged parts.

STEP 2. Check the wiring harness between joint connector (CAN1) C-105 and A/C-ECU connector C-22 for open circuit.

CAUTION: Strictly observe the specified wiring harness repair procedure.

1. Disconnect joint connector (CAN1) C-105 and A/C-ECU connector C-22, and check the wiring harness.




2. Check the wiring harness between joint connector (CAN1) C-105 (terminal 1) and A/C-ECU connector C-22 (terminal 11)

OK: Continuity exists (2 ohms or less)




3. Check the wiring harness between joint connector (CAN1) C-105 (terminal 12) and A/C-ECU connector C-22 (terminal 12)

OK: Continuity exists (2 ohms or less)

Q : Is the wiring harness between joint connector (CAN1) C-105 and A/C-ECU connector C-22 in good condition?

YES : Check the power supply circuit of the A/C-ECU. Refer to Heating and A/C and Ventilation, Diagnosis. Symptom Chart

NO : Repair the wiring harness between joint connector (CAN1) C-105 and A/C-ECU connector C-22.