Diagnostic 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.

Eclipse:

Eclipse Spyder (Part 1):

Eclipse Spyder (Part 2):

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 JUDGEMENT 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.

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.
- The test wiring harness should be used.













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.

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. Refer to MFI Diagnosis - Symptom procedures, Communication with PCM only is not possible [2.4L engine] or MFI Diagnosis - Symptom procedures, Communication with ECM [M/T] or PCM [A/T] only is not possible [3.8L engine]. Symptom Chart

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.