Diagnostics Item 10

DIAGNOSTIC ITEM 10: Diagnose when the scan tool cannot receive the data sent by the ECM [M/T] or the PCM [A/T].

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 [M/T] or PCM [A/T]" when the scan tool MB991958 checks the periodically sent data from each ECU and cannot receive the ECM [M/T] or PCM [A/T] data only.

TROUBLE JUDGMENT CONDITIONS

Scan tool MB991958 judges the trouble when the periodically sent data from the ECM [M/T] or PCM [A/T] cannot be received and sent.

TROUBLESHOOTING HINTS

- The wiring harness may be defective (open circuit between TCL/ASC-ECU and ECM [M/T] or PCM [A/T])
- The connector may be defective (poor connection of ECM [M/T] or PCM [A/T] connector and TCL/ASC-ECU connector)
- Power supply circuit malfunction of the ECM [M/T] or PCM [A/T]
- The ECM [M/T] or PCM [A/T] may be defective

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra fine probe
- MB991923: Power plant ECU Check Harness
- MB991997: ASC Check Harness

STEP 1. Check TCL/ASC-ECU connector A-38 and ECM connector [M/T] or PCM connector [A/T] 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. For details refer to Precautions When CAN Bus Line(s) are Repaired.

Q. Are TCL/ASC-ECU connector A-38 and ECM connector[ M/T] or PCM connector[ A/T] B-18 in good condition?

YES Go to Step 2.

NO Repair the damaged parts.

STEP 2. Check the CAN bus lines between the TCL/ASC-ECU and the ECM [M/T] or PCM [A/T]. Measure the resistance between TCL/ASC-ECU connector A-38 and ECM connector [M/T] or PCM connector [A/T] B-18.

CAUTION:

- A digital multimeter should be used. For details refer to Precautions When CAN Bus Line(s) are Repaired .
- The test wiring harness should be used. For details refer to Precautions When CAN Bus Line(s) are Repaired .













(1)Disconnect TCL/ASC-ECU connector A-38 and ECM [M/T] or PCM connector [A/T] B-18, and measure the resistance between each wiring harness side connector.





(2)Measure the resistance between TCL/ASC-ECU connector A-38 (terminal 11) and ECM connector [M/T] or PCM connector [A/T] B-18 (terminal 17).
OK: 2 ohms or less






(3)Measure the resistance between TCL/ASC-ECU connector A-38 (terminal 15) and ECM connector [M/T] or PCM connector [A/T] B-18 (terminal 18).
OK: 2 ohms or less

CAUTION:
Strictly observe the specified wiring harness repair procedure. For details refer to Precautions on How to Repair the CAN Bus Line(s).

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

YES Go to Step 3.

NO Repair the wiring harness between the TCL/ASC-ECU connector A-38 and the ECM connector [M/T] or PCM connector [A/T] B-18.

STEP 3. Check the CAN bus lines inside the TCL/ASC-ECU. Measure the resistance at TCL/ASC-ECU connector A-38.





(1)Disconnect TCL/ASC-ECU A-38, and measure the resistance at the component side of TCL/ASC-ECU connector A-38.





(2)Measure the resistance between TCL/ASC-ECU connector A-38 (terminals 11 and 27).
OK: 2 ohms or less






(3)Measure the resistance between TCL/ASC-ECU connector A-38 (terminals 13 and 15).
OK: 2 ohms or less

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

YES Go to Step 4.

NO Replace the TCL/ASC-ECU.

STEP 4. Check the terminator resistor inside the ECM [M/T] or PCM [A/T]. Measure the resistance at ECM [M/T] or PCM [A/T] connector B-18.









(1)Disconnect ECM [M/T] or PCM [A/T] connector B-18, and measure the resistance at the component side of ECM [M/T] or PCM [A/T] connector B-18.





(2)Measure the resistance between ECM [M/T] or PCM [A/T] connector B-18 (terminals 17 and 18).
OK: 120± 20 ohms

Q. Does the resistance measure 120± 20 ohms?

YES Diagnose the engine. Inspection Procedure 1 MFI Diagnosis - Symptom procedures, Communication with ECM [M/T] or PCM [A/T] only is not possible Inspection Procedure 1.

NO Replace the ECM [M/T] or PCM [A/T]. When the ECM [M/T] or PCM [A/T] is replaced, register the encrypted code. Immobilizer System.