Diagnostic Item 3
DIAGNOSTIC ITEM 3: Diagnose shorts between CAN_H and L linesPart 1:
Part 1:
Part 2:
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 scan tool MB991958 judges a short between CAN_H and CAN_L line when all data from ECU cannot be received while checking periodically sent data from each ECU even if the voltage is normal.
TROUBLE JUDGEMENT CONDITIONS
The scan tool MB991958 judges the trouble when it is impossible to send and receive the all ECU periodically sent data and the voltage of CAN_H and CAN_L line is 4.0 volts or less and 1.0 volt or more.
TROUBLESHOOTING HINTS
- The wiring harness may be defective [a short between CAN_H and CAN_L line, open circuit between the data link connector and the joint connector (3) or open circuit between the combination meter connector and the joint connector (3)]
NOTE: The scan tool MB991958 cannot receive all the periodically sent data from each ECU by the open circuit of harness between the data link connector and the joint connector (3). In addition, the scan tool MB991958 measures the voltage itself and shows 2.5 volts due to the open circuit of harness. Therefore, it is judged as a short between CAN_H and CAN_L line.
- The connector may be defective (short in the connector)
- Each ECU may be defective (short between CAN_H and CAN_L line)
DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra fine probe
- MB991970: ABS Check Harness
STEP 1. Check joint connector (3) C-03 and intermediate connector C-24
CAUTION: The strand end of the twisted wire should be within 10 cm (4.0 inches) from the connector.
Visually check if there is a short between lines due to the foreign obstacles or deformation of short pin in the connector.
Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the connector, or replace the joint connector (3).
STEP 2. Check the lines between the CAN_H and L lines of the front wiring harness for a short circuit. Measure the resistance at intermediate connector C-24.
CAUTION:
- A digital multimeter should be used.
- The test wiring harness should be used.
CAUTION: Disconnect the negative battery terminal.
1. Disconnect the negative battery terminal.
2. Disconnect intermediate connector C-24, and measure the resistance at the male side (at front wiring harness side).
3. Measure the resistance between intermediate connector terminals 11 and 12.
OK: 120 ± 20 ohms
Q: Is the check result normal?
YES: Go to Step (3)
NO: Go to Step 12.
STEP 3. Check the CAN_H and L lines between joint connector (3) and the combination meter for a short circuit. Measure the resistance at joint connector (3) C-03.
1. Disconnect the negative battery terminal.
2. Disconnect joint connector (3) C-03, and measure the resistance at the wiring harness side of joint connector (3) C-03.
3. Measure the resistance between joint connector (3) terminals 4 and 15.
OK: 120 ± 20 ohms
Q: Is the check result normal?
YES: Go to Step 4.
NO: Go to Step 8.
STEP 4. Check the CAN_H and L lines between joint connector (3) and the ETACS-ECU for a short circuit. Measure the resistance at joint connector (3) C-03.
1. Disconnect the negative battery terminal.
2. Disconnect joint connector (3) C-03, and measure the resistance at the wiring harness side of joint connector (3) C-03.
3. Measure the resistance between joint connector (3) terminals 5 and 16.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Go to Step 5.
NO: Go to Step 9.
STEP 5. Check the CAN_H and L lines between joint connector (3) and the A/C-ECU for a short circuit. Measure the resistance at joint connector (3) C-03.
1. Disconnect the negative battery terminal.
2. Disconnect joint connector (3) C-03, and measure the resistance at the wiring harness side of joint connector (3) C-03.
3. Measure the resistance between joint connector (3) terminals 6 and 17.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Go to Step 6.
NO: Go to Step 10.
STEP 6. Check the CAN_H and L lines between joint connector (3) and the SRS-ECU for a short circuit. Measure the resistance at joint connector (3) C-03.
1. Disconnect the negative battery terminal.
2. Disconnect joint connector (3) C-03, and measure the resistance at the wiring harness side of joint connector (3) C-03.
3. Measure the resistance between joint connector (3) terminals 3 and 14.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Go to Step 7.
NO: Go to Step 11.
STEP 7. Check the CAN_H and L lines between joint connector (3) and the data link connector for a short circuit. Measure the resistance at joint connector (3) C-03.
1. Disconnect the negative battery terminal.
2. Disconnect joint connector (3) C-03, and measure the resistance at the wiring harness side of joint connector (3) C-03.
3. Measure the resistance between joint connector (3) terminals 7 and 18.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Repair the wiring harness between joint connector (3) and the intermediate connector.
NO: Repair the wiring harness between joint connector (3) and the data link connector.
STEP 8. Check the combination meter for short circuit. Measure the resistance at combination meter connector C-04.
NOTE: The failure could be caused by the open circuit of harness between combination meter and joint connector (3), therefore, check the open circuit as well as the short.
1. Disconnect the negative battery terminal.
2. Disconnect combination meter C-04, and measure the resistance at the component side of combination meter connector C-04.
3. Measure the resistance between combination meter connector terminals 3 and 4.
OK: 120 ± 20 ohms
Q: Is the check result normal?
YES: Check the combination meter connector, and repair if necessary. Repair the open circuit of harness between the joint connector (3) and the combination meter connector or the short between lines if the combination meter connector is normal.
NO: Check the combination meter connector, and repair if necessary. If the combination meter connector is in good condition, replace the combination meter.
STEP 9. Check the ETACS-ECU for short circuit. Measure the resistance at ETACS-ECU connector C-218.
1. Disconnect the negative battery terminal.
2. Disconnect ETACS-ECU connector C-218, and measure the resistance at the component side of ETACS-ECU connector C-218.
3. Measure the resistance between ETACS-ECU connector terminals 72 and 73.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Check the ETACS-ECU connector, and repair if necessary. If the ETACS-ECU connector is in good condition, repair the wiring harness between joint connector (3) and the ETACS-ECU connector.
NO: Check the ETACS-ECU connector, and repair if necessary. If the ETACS-ECU connector is in good condition, replace the ETACS-ECU. When the ETACS-ECU is replaced, register the encrypted code. Refer to Chassis Electrical - Encrypted Code Registration Criteria Table.
STEP 10. Check the A/C-ECU for short circuit. Measure the resistance at A/C-ECU connector C-14
CAUTION: A digital multimeter should be used.
1. Disconnect the negative battery terminal.
2. Disconnect A/C-ECU connector C-14
3. Measure the resistance between A/C-ECU connector terminals 5 and 6.
OK: 1 k ohm or more
4. Measure the resistance between A/C-ECU connector terminals 14 and 15.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Check the A/C-ECU connector, and repair if necessary. If the A/C-ECU connector is in good condition, repair the wiring harness between joint connector (3) and the A/C-ECU connector.
NO: Check the A/C-ECU connector, and repair if necessary. If the A/C-ECU connector is in good condition, replace the A/C-ECU.
STEP 11. Check the SRS-ECU for short circuit. Measure the resistance at SRS-ECU connector C-123.
1. Disconnect the negative battery terminal.
2. Disconnect SRS-ECU connector C-123, and measure the resistance at the component side of SRS-ECU connector C-123.
3. Measure the resistance between SRS-ECU connector terminals 32 and 43.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Check the SRS-ECU connector, and repair if necessary. If the SRS-ECU connector is in good condition, repair the wiring harness between joint connector (3) and SRS-ECU connector.
NO: Check the SRS-ECU connector, and repair if necessary. If the SRS-ECU connector is in good condition, replace the SRS-ECU.
STEP 12. Check the ECM
1. Disconnect the negative battery terminal.
2. Disconnect ECM
3. Measure the resistance between ECM
OK: 120 ± 20 ohms
Q: Is the check result normal?
YES: Check the ECM
NO: Check the ECM
STEP 13. Check the ABS-ECU
1. Disconnect the negative battery terminal.
2. Disconnect ABS-ECU connector A-02
3. Measure the resistance between ABS-ECU connector terminals 2 and 8.
OK: 1 k ohm or more
4. Measure the resistance between ABS/TCL-ECU connector terminals 13 and 27.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Check the ABS-ECU
NO: Check the ABS-ECU
STEP 14. Check the CAN_L and H lines between the ECM
1. Disconnect the negative battery terminal.
2. Disconnect ECM connector
3. Measure the resistance between ABS-ECU connector terminals 4 and 6.
OK: 1 k ohm or more
4. Measure the resistance between ABS/TCL-ECU connector terminals 11 and 15.
OK: 1 k ohm or more
Q: Is the check result normal?
YES
YES
NO: Repair the wiring harness between ECM connector
STEP 15. Check the CAN_L and H lines between the ABS-ECU
1. Disconnect the negative battery terminal.
2. Disconnect intermediate connector C-24 and ABS-ECU connector A-02
3. Measure the resistance between intermediate connector terminals 11 and 12.
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Repair the wiring harness between joint connector (3) and data link connector.
NO: Repair the wiring harness between intermediate connector C-24 and ABS-ECU
STEP 16. Check the convertible top control module for short circuit. Measure the resistance at convertible top control module connector D-45.
1. Disconnect the negative battery terminal.
2. Disconnect convertible top control module connector D-45, and measure the resistance at the component side of convertible top control module connector D-45.
3. Measure the resistance between convertible top control module connector D-45 (terminals 37 and 38).
OK: 1 k ohm or more
4. Measure the resistance between convertible top control module connector D-45 (terminals 38 and 49).
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Check the convertible top control module connector, and repair if necessary. If the convertible top control module connector is in good condition, go to Step 17.
NO: Check the convertible top control module connector, and repair if necessary. If the convertible top control module connector is in good condition, replace the convertible top control module.
STEP 17. Check the CAN_L and H lines between the convertible top control module connector and the ABS-ECU
1. Disconnect the negative battery terminal.
2. Disconnect convertible top control module D-45 and ABS-ECU connector A-02
3. Measure the resistance between ABS-ECU connector A-02 (terminals 4 and 6).
OK: 1 k ohm or more
4. Measure the resistance between ABS/TCL-ECU connector A-03 (terminals 11 and 15).
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Go to Step 18.
NO: Check the intermediate connector C-26, and repair if necessary. If the intermediate connector C-26 in good condition, repair the wiring harness between ABS-ECU
STEP 18. Check the CAN_L and H lines between the convertible top control module connector D-45 and the intermediate connector C-23 for a short circuit. Measure the resistance at intermediate connector C-23.
1. Disconnect the negative battery terminal.
2. Disconnect intermediate connector C-23 and convertible top control module connector D-45, and measure the resistance at the male side of intermediate connector C-23 (at front wiring harness side).
3. Measure the resistance between intermediate connector C-23 (terminals 22 and 23).
OK: 1 k ohm or more
Q: Is the check result normal?
YES: Repair the wiring harness between joint connector (3) and data link connector.
NO: Repair the wiring harness between intermediate connector C-23 and convertible top control module connector D-45.