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 Communication Circuit (Part 1):

CAN 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 (CAN 1) C-103 and A/C-ECU connector C-109 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-103 and A/C-ECU connector C-109 in good condition?

YES : Go to Step 2.

NO : Repair the damaged parts.

STEP 2. Check the wiring harness between joint connector (CAN1) C-103 and A/C-ECU connector C-109.

CAUTION: Strictly observe the specified wiring harness repair procedure.

1. Disconnect joint connector (CAN1) C-103 and A/C-ECU connector C-301, and check the wiring harness.
2. Check the wiring harness between joint connector (CAN1) C-103 (terminal No.9) and A/C-ECU connector C-109 (terminal No.11)
3. Check the wiring harness between joint connector (CAN1) C-103 (terminal No.22) and A/C-ECU connector C-109 (terminal No. 12)

Q: Is the wiring harness between joint connector (CAN1) C-103 and A/C-ECU connector C-109 in good condition?

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

NO : Repair the wiring harness between joint connector (CAN1) C-103 and A/C-ECU connector C-109.