Diagnostics Item 6
DIAGNOSTIC ITEM 6: Diagnose when the scan tool cannot receive the data sent by ETACS-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.
FUNCTION
The diagnostic result demonstrates that "the scan tool cannot receive the sent data from the ETACS-ECU" when the scan tool MB991958 checks the periodically sent data from each ECU and cannot receive the ETACS-ECU data only.
TROUBLE JUDGMENT CONDITIONS
Scan tool MB991958 judges the trouble when the periodically sent data from ETACS-ECU cannot be received and sent.
TROUBLESHOOTING HINTS
- The wiring harness may be defective [open circuit between ETACS-ECU and joint connector (3)]
- The connector may be defective [poor connection of joint connector (3) or ETACS-ECU connector]
- Power supply circuit malfunction of the ETACS-ECU
- The ETACS-ECU may be defective
DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra fine probe
STEP 1. Check joint connector (3) C-03 and ETACS-ECU connector C-218 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 (4.0 inches) from the connector. For details refer to Precautions When CAN Bus Line(s) are Repaired.
Check the joint connector at the wiring harness side for loose, corroded or damaged terminals, or terminals pushed back in the connector, and also check the short pin behind the connector for corrosion, deformation and delamination.
Q. Are joint connector (3) C-03 and ETACS-ECU connector C-218 in good condition?
YES Go to Step 2.
NO Repair the damaged parts. Replace the joint connector as necessary.
STEP 2. Check the CAN bus lines between joint connector (3) and the ETACS-ECU. Measure the resistance between joint connector (3) C-03 and ETACS-ECU connector C-218.
CAUTION:
- A digital multimeter should be used. For details refer to Precautions When CAN Bus Line(s) are Repaired .
- The test wiring harness should be used. For details refer to Precautions When CAN Bus Line(s) are Repaired .
(1)Disconnect joint connector (3) C-03 and ETACS-ECU connector C-218, and measure the resistances at the wiring harness sides of joint connector (3) C-03 and ETACS-ECU connector C-218.
(2)Measure the resistance between joint connector (3) terminal 5 and ETACS-ECU connector terminal 72.
OK: 2 ohms or less
(3)Measure the resistance between joint connector (3) terminal 16 and ETACS-ECU connector terminal 73.
OK: 2 ohms or less
CAUTION:
Strictly observe the specified wiring harness repair procedure. For details refer to Precautions on How to Repair the CAN Bus Line(s).
Q. Do all the resistances measure 2 ohms or less?
YES Diagnose the ETACS-ECU. Inspection Procedure A-3.
NO Repair the wiring harness between joint connector (3) and the ETACS-ECU connector.