Diagnostic Item 1

DIAGNOSTIC ITEM 1: 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.

Diagnosis CAN Communication Circuit:

FUNCTION
When the CAN bus diagnosis is carried out, the scan tool communicates with the ETACS-ECU. If a communication flag is not set for the ETACS-ECU, the ETACS-ECU will be diagnosed as a communication error.

TROUBLE JUDGMENT CONDITIONS
If a communication flag is not set for the
ETACS-ECU, the scan tool determines that there is a failure.

TROUBLESHOOTING HINTS
- Malfunction of the connector (data link connector or ETACS-ECU connector improperly connected)
- Malfunction of the wiring harness (open circuit, short to ground, short to power supply between the data link connector and the ETACS-ECU connector, line-to-line short, or power supply to the ETACS-ECU)
- Malfunction of ETACS-ECU

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 data link connector C-40 and ETACS-ECU connector C-301 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 data link connector C-40 and ETACS-ECU connector C-301 in good condition?

YES : Go to Step 2.

NO : Repair the damaged parts.

STEP 2. Check the wiring harness between data link connector C-40 and ETACS-ECU connector C-301 for open circuit.

CAUTION: Strictly observe the specified wiring harness repair procedure.

1. Disconnect the scan tool and ETACS-ECU connector C-301, and check the wiring harness.







2. Check the wiring harness between data link connector C-40 (terminal 6) and ETACS-ECU connector C-301 (terminal 5) [CAN_H]

OK: Continuity exists (2 ohms or less)







3. Check the wiring harness between data link connector C-40 (terminal 14) and ETACS-ECU connector C-301 (terminal 4) [CAN_L]

OK: Continuity exists (2 ohms or less)

Q: Is the wiring harness between data link connector C-40 and ETACS-ECU connector C-301 in good condition?

YES : Go to Step 3.

NO : Repair the wiring harness between data link connector C-40 and ETACS-ECU connector C-301.

STEP 3. Check the wiring harness between data link connector C-40 and ETACS-ECU connector C-301 for a short to ground. Measure the resistance at data link connector C-40.

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

1. Disconnect the scan tool and ETACS-ECU connector C-301, and measure the resistance at the wiring harness side of data link connector C-40.







2. Measure the resistance between data link connector terminal 6 and body ground. [CAN_H]

OK: 1 kohms or more







3. Measure the resistance between data link connector terminal 14 and body ground. [CAN_L]

OK: 1 kohms or more

Q: Do all the resistances measure 1 kohms or more?

YES : Go to Step 4.

NO : Repair the wiring harness between data link connector C-40 and ETACS-ECU connector C-301.

STEP 4. Check the wiring harness between data link connector C-40 and ETACS-ECU connector C-301 for a short to the power supply. Measure the voltage at data link connector C-40.

1. Disconnect the scan tool and ETACS-ECU connector C-301, and measure the resistance at the wiring harness side of data link connector C-40.
2. Turn the ignition switch to the "ON" position.







3. Measure the voltage between data link connector terminal 6 and body ground. [CAN_H]

OK: 1 V or less







4. Measure the voltage between data link connector terminal 14 and body ground. [CAN_L]

OK: 1 V or less

Q: Do all the voltage measure 1 V or less?

YES : Go to Step 5.

NO : Repair the wiring harness between data link connector C-40 and ETACS-ECU connector C-301.

STEP 5. Check the wiring harness between data link connector C-40 and ETACS-ECU connector C-301 for line-to-line short. Measure the resistance at data link connector C-40.

1. Disconnect the scan tool and ETACS-ECU connector C-301, and measure the resistance at the wiring harness side of data link connector C-40.







2. Measure the resistance between data link connector terminal 6 and 14.

OK: No continuity

Q: Is the check result normal?

YES : Go to Step 6.

NO : Repair the wiring harness between data link connector C-40 and ETACS-ECU connector C-301.

STEP 6. 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.

NO : Replace the ETACS-ECU.