Diagnostics Item 21

DIAGNOSTIC ITEM 21: Diagnose when the scan tool cannot receive the data sent by CAN box unit.

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.














FUNCTION

If the scan tool MB991958 cannot communicate with the CAN box unit, this diagnosis result will be set.

TROUBLE JUDGMENT CONDITIONS

If a communication flag is not set for the CAN box unit, the ETACS-ECU determines that there is a failure.

TROUBLESHOOTING HINTS

- Malfunction of the connector [joint connector (CAN1), CAN box unit connector improperly connected]
- Malfunction of the wiring harness [open circuit between the CAN box unit connector and the joint connector (CAN1), power supply circuit to the CAN box unit]
- Malfunction of the CAN box unit

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check joint connector (CAN1) C-105, CAN box unit connector C-15 and intermediate connector C-108 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. For details refer to Precautions When CAN Bus Line(s) are Repaired.

Q. Are joint connector (CAN1) C-105, CAN box unit connector C-15 and intermediate connector C-108 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 CAN box unit connector C-15 for open circuit.

CAUTION:
Strictly observe the specified wiring harness repair procedure.
For details refer to Precautions When CAN Bus Line(s) are Repaired.

(1)Disconnect joint connector (CAN1) C-105 and CAN box unit connector C-15, and check the wiring harness.





(2)Check the wiring harness between joint connector (CAN1) C-105 (terminal 5) and CAN box unit connector C-15 (terminal 8)
OK: Continuity exists (2ohms or less)






(3)Check the wiring harness between joint connector (CAN1) C-105 (terminal 16) and CAN box unit connector C-15 (terminal 9)
OK: Continuity exists (2ohms or less)

Q. Is the wiring harness between joint connector (CAN1) C-105 and CAN box unit connector C-15 in good condition?

YES Check the power supply circuit of the CAN box unit. Symptom Chart.

NO Repair the wiring harness between joint connector (CAN1) C-105 and CAN box unit connector C-15.