Diagnostic Item 3

DIAGNOSTIC ITEM 3: Abnormal short between the CAN-C bus lines.

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 a line-to-line short is present in the CAN-C lines, this diagnosis result will be set.

TROUBLE JUDGEMENT CONDITIONS
If only diagnostic trouble code U0001 is set, the ETACS-ECU determines that there is a failure.

TROUBLESHOOTING HINTS
- Malfunction of the connector (joint connectors or ECU connectors improperly connected)
- Malfunction of the wiring harness (line-to-line short in the CAN-C main or sub bus lines)
- Malfunction of the ECU (ECU on CAN-C lines failed)

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

- MB991970: ABS Check Harness

STEP 1. Check joint connector (CAN2) C-05 and joint connector (CAN3) C-124 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 (CAN2) C-05 and joint connector (CAN3) C-124 in good condition?

YES : Go to Step 2.

NO : Repair the damaged parts.

STEP 2. Check the wiring harness between joint connector (CAN3) C-124 and ECM connector B-109 for line-to-line short. Measure the resistance at joint connector (CAN3) C-124.

CAUTION:
- Disconnect the negative battery terminal.
- A digital multimeter should be used.
- The test wiring harness should be used.

1. Disconnect joint connector (CAN3), and check that there is continuity at the harness side of joint connector (CAN3).

2. Check that there is continuity between joint connector (CAN3) terminals 4 and 15.

OK: No continuity

Q: Is the check result normal?

YES : Go to Step 3.

NO : Go to Step 6.

STEP 3. Check the wiring harness between joint connector (CAN3) C-124 and ABS-ECU connector A-01 for line-to-line short. Measure the resistance at joint connector (CAN3) C-124.

1. Disconnect joint connector (CAN3), and check that there is continuity at the harness side of joint connector (CAN3).

2. Check that there is continuity between joint connector (CAN3) terminals 6 and 19.

OK: No continuity

Q: Is the check result normal?

YES : Go to Step 5.

YES : Go to Step 4.

NO (the check result is not normal.) : Go to Step 7.

STEP 4. Check the wiring harness between joint connector (CAN3) C-124 and TCM connector C-41 for line-to-line short. Measure the resistance at joint connector (CAN3) C-124.

1. Disconnect joint connector (CAN3), and check that there is continuity at the harness side of joint connector (CAN3).

2. Check that there is continuity between joint connector (CAN3) terminals 7 and 20.

OK: No continuity

Q: Is the check result normal?

YES : Go to Step 5.

NO : Go to Step 8.

STEP 5. Check the wiring harness between joint connector (CAN2) C-05 and ETACS-ECU connector C-301 for line-to-line short. Measure the resistance at joint connector (CAN2) C-05.

1. Disconnect joint connector (CAN2), and check that there is continuity at the harness side of joint connector (CAN2).

2. Check that there is continuity between joint connector (CAN2) terminals 6 and 19.

OK: No continuity

Q: Is the check result normal?

YES : Check intermediate connector C-128, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between joint connector (CAN2) C-05 and joint connector (CAN3) C-124.

NO : Go to Step 9.

STEP 6. Using scan tool MB991958, diagnose the CAN bus line. (checking the ECM for internal short)

CAUTION:
- Strictly observe the specified wiring harness repair procedure.
- To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1. Disconnect ECM connector B-109.

2. Connect scan tool MB991958 to the data link connector.
3. Turn the ignition switch to the "ON" position.

1. Disconnect ABS-ECU connector A-01.
2. Connect scan tool MB991958 to the data link connector.
3. Turn the ignition switch to the "ON" position.

2. Connect scan tool MB991958 to the data link connector.
3. Turn the ignition switch to the "ON" position.

4. Diagnose CAN bus lines, and check if the scan tool MB991958 screen is as shown in the figure.

OK: The display of the scan tool MB991958 is as shown in the figure.

Q: Does scan tool MB991958 screen correspond to the illustration?

YES : Repair the wiring harness between TCM connector C-41 and joint connector (CAN3) C-124.

NO : Check TCM connector C-41, and repair if necessary. If the TCM connector is in good condition, replace the TCM.

STEP 9. Check the wiring harness between joint connector (CAN2) C-05 and ETACS-ECU connector C-301 for line-to-line short. Measure the resistance at joint connector (CAN2) C-05.

1. Disconnect joint connector (CAN2) and ETACS-ECU connector, and check that there is continuity at the harness side of joint connector (CAN2).
2. Check that there is continuity between joint connector (CAN2) terminals 6 and 19.

OK: No continuity

Q: Is the check result normal?

YES : Go to Step 10.

NO : Repair the wiring harness between joint connector (CAN2) C-05 and ETACS-ECU connector C-301.

STEP 10. Using scan tool MB991958, diagnose the CAN bus line.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.

3. Diagnose CAN bus lines, and check if the scan tool screen is as shown in the illustration.

Q: Does the scan tool screen correspond to the illustration?

YES : The trouble can be an intermittent malfunction (Refer to general (Body and Chassis) How to use Troubleshooting/inspection Service Points How to Cope with Intermittent Malfunction).

NO : Replace the ETACS-ECU.