Diagnostic Item 4

DIAGNOSTIC ITEM 4: Diagnose shorts in the ground to CAN-C bus line.

CAN Communication Circuit (Part 1):

CAN Communication Circuit (Part 2):

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

TROUBLE JUDGEMENT CONDITIONS
If DTC U1120 is set, the ETACS-ECU determines that there is a failure.

TROUBLESHOOTING HINTS
- Malfunction of the connector (short to ground inside connector)
- Malfunction of the wiring harness (short to ground in the CAN-C main or sub bus lines)
- Malfunction of the ECU (ETACS-ECU, or ECUs 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

STEP 1. Check the wiring harness between joint connector (CAN2) C-05 and ETACS-ECU connector C-301 for a short to ground. Measure the resistance at joint connector (CAN2) C-05.

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

1. Disconnect joint connector (CAN2), and measure the resistance at the wiring harness side of joint connector (CAN2).

2. Measure the resistance between joint connector (CAN2) terminal 6 and body ground.

OK: 1 kilo ohm or more

3. Measure the resistance between joint connector (CAN2) terminal 19 and body ground.

OK: 1 kilo ohm or more

Q: Do all the resistances measure 1 kilo ohm or more?

YES : Go to Step 2.

NO : Go to Step 5.

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

1. Disconnect joint connector (CAN3), and measure the resistance at the wiring harness side of joint connector (CAN3).

2. Measure the resistance between joint connector (CAN3) terminal 4 and body ground.

OK: 1 kilo ohm or more

3. Measure the resistance between joint connector (CAN3) terminal 15 and body ground.

OK: 1 kilo ohm or more

Q: Do all the resistances measure 1 kilo ohm or more?

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 a short to ground. Measure the resistance at joint connector (CAN3) C-124.

1. Disconnect joint connector (CAN3), and measure the resistance at the wiring harness side of joint connector (CAN3).

2. Measure the resistance between joint connector (CAN3) terminal 6 and body ground.

OK: 1 kilo ohm or more

3. Measure the resistance between joint connector (CAN3) terminal 19 and body ground.

OK: 1 kilo ohm or more

Q: Do all the resistances measure 1 kilo ohm or more?

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.

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 a short to ground. Measure the resistance at joint connector (CAN3) C-124.

1. Disconnect joint connector (CAN3), and measure the resistance at the wiring harness side of joint connector (CAN3).

2. Measure the resistance between joint connector (CAN3) terminal 7 and body ground.

OK: 1 kilo ohm or more

3. Measure the resistance between joint connector (CAN3) terminal 20 and body ground.

OK: 1 kilo ohm or more

Q: Do all the resistances measure 1 kilo ohm or more?

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 8.

STEP 5. Using scan tool MB991958, diagnose the CAN bus line. (checking the ETACS-ECU for internal short to ground)

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 ETACS-ECU connector C-301.

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 ETACS-ECU connector C-301 and joint connector (CAN2) C-05.

NO : Check ETACS-ECU connector C-128, and repair if necessary. If the ETACS-ECU connector is in good condition, replace the ETACS-ECU.

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

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.

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 ECM connector B-109 and joint connector (CAN3) C-124.

NO : Check ECM connector B-109, and repair if necessary. If the ECM connector is in good condition, replace the ECM.

STEP 7. Using scan tool MB991958, diagnose the CAN bus line. (checking the ABS-ECU for internal short to ground)

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 ABS-ECU connector A-01.

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 ABS-ECU connector A-01 and joint connector (CAN3) C-124.

NO : Check ABS-ECU connector A-01, and repair if necessary. If the ABS-ECU connector is in good condition, replace the ABS-ECU.

STEP 8. Using scan tool MB991958, diagnose the CAN bus line. (checking the TCM for internal short to ground)

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 TCM connector C-41.

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