Diagnostic Item 10

DIAGNOSTIC ITEM 10: Diagnose when the scan tool cannot receive the data sent by the ECM or the PCM .

Part 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 diagnostic result demonstrates that "the scan tool cannot receive the sent data from the ECM or PCM " when the scan tool MB991958 checks the periodically sent data from each ECU and cannot receive the ECM or PCM data only.

TROUBLE JUDGEMENT CONDITIONS
Scan tool MB991958 judges the trouble when the periodically sent data from the ECM or PCM cannot be received and sent.

TROUBLESHOOTING HINTS
- The wiring harness may be defective (open circuit between ABS-ECU or ABS/TCL-ECU and ECM or PCM )
- The connector may be defective (poor connection of ECM or PCM connector and ABS-ECU or ABS/TCL-ECU connector)
- Power supply circuit malfunction of the ECM or PCM
- The ECM or PCM may be defective

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra fine probe
- MB991970: ABS Check Harness

STEP 1. Check ABS-ECU connector A-02 or ABS/TCL-ECU connector A-03 and ECM connector or PCM connector B-18 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.

Q: Are ABS-ECU connector A-02 or ABS/TCL-ECU connector A-03 and ECM connector or PCM connector B-18 in good condition?

YES:: Go to Step 2.

NO: Repair the damaged parts.

STEP 2. Check the CAN bus lines between the ABS-ECU or ABS/TCL-ECU and the ECM or PCM . Measure the resistance between ABS-ECU connector A-02 or ABS/TCL-ECU connector and ECM connector or PCM connector B-18.

CAUTION:
- A digital multimeter should be used.
- The test wiring harness should be used.

1. Disconnect ABS-ECU connector A-02 or ABS/TCL-ECU connector A-03 and ECM or PCM connector B-18, and measure the resistance between each wiring harness side connector.

2. Measure the resistance between ABS-ECU connector A-02 (terminal 4) and ECM connector or PCM connector B-18 (terminal 17).

OK: 2 ohms or less

3. Measure the resistance between ABS-ECU connector A-02 (terminal 6) and ECM connector or PCM connector B-18 (terminal 18).

OK: 2 ohms or less

4. Measure the resistance between ABS/TCL-ECU connector A-03 (terminal 11) and ECM connector or PCM connector B-18 (terminal 17).

OK: 2 ohms or less

5. Measure the resistance between ABS/TCL-ECU connector A-03 (terminal 15) and ECM connector or PCM connector B-18 (terminal 18).

OK: 2 ohms or less

CAUTION: Strictly observe the specified wiring harness repair procedure.

Q: Do all the resistances measure 2 ohms or less?

YES: Diagnose the engine. Refer to MFI diagnosis.

NO: Repair the wiring harness between the ABS-ECU connector A-02 or ABS/TCL-ECU connector A-03 and the ECM connector or PCM connector B-18.