Diagnostic Item 14

DIAGNOSTIC ITEM 14: Diagnose when the scan tool cannot receive the data sent by the ECM or the PCM and convertible top control module.

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 and convertible top control module" when the scan tool MB991958 checks the periodically sent data from each ECU and cannot receive convertible top control module and ECM or powertrain control system data only.

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

TROUBLESHOOTING HINTS
- The wiring harness may be defective [open circuit between convertible top control module and joint connector (3) ]
- The connector may be defective [poor connection of joint connector (3) or convertible top control module connector]
- The convertible top control module may be defective (internal open circuit)
- The ECM or PCM may be defective (internal open circuit)

DIAGNOSIS

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

STEP 1. Check joint connector (3) C-03 and convertible top control module connector D-45 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 joint connector (3) C-03 and convertible top control module connector D-45 in good condition?

YES: Go to Step 2.

NO: Repair the damaged parts. Replace the joint connector as necessary.

STEP 2. Check the CAN bus lines between intermediate connector C-23 and joint connector (3). Measure the resistance between intermediate connector C-23 and joint connector (3) C-03.

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

1. Disconnect intermediate connector C-23 and joint connector (3) C-03, and measure the resistance between the wiring harness side connector of joint connector (3) C-03 and the male side connector of intermediate connector C-23 (at front wiring harness side).
2. Turn the ignition switch to the "LOCK" (OFF) position.

CAUTION: Disconnect the negative battery terminal.

3. Disconnect the negative battery terminal.




4. Measure the resistance between intermediate connector C-23 (terminal 22) and joint connector (3) C-03 (terminal 9).

OK: 2 ohms or less




5. Measure the resistance between intermediate connector C-23 (terminal 23) and joint connector (3) C-03 (terminal 20).

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: If all the resistances measure 2 ohms or less, go to Step 3.

NO: If either of the resistances measures more than 2 ohms or all the resistances measure more than 2 ohms, repair the wiring harness between intermediate connector C-23 and the joint connector (3) C-03.

STEP 3. Check the CAN bus lines between intermediate connector C-23 and the convertible top control module connector D-45. Measure the resistance between intermediate connector C-23 and convertible top control module connector D-45.

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







1. Disconnect intermediate connector C-23 and convertible top control module connector D-45, and measure the resistance between the wiring harness side connector of convertible top control module connector D-45 and the male side connector of intermediate connector C-23 (at front wiring harness side).
2. Turn the ignition switch to the "LOCK" (OFF) position.

CAUTION: Disconnect the negative battery terminal.

3. Disconnect the negative battery terminal.




4. Measure the resistance between intermediate connector C-23 (terminal 22) and convertible top control module connector D-45 (terminal 48).

OK: 2 ohms or less




5. Measure the resistance between intermediate connector C-23 (terminal 23) and convertible top control module connector D-45 (terminal 49).

OK: 2 ohms or less

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

YES: If all the resistances measure 2 ohms or less, go to Step 4.

NO: If either of the resistances measures more than 2 ohms or all the resistances measure more than 2 ohms, repair the wiring harness between intermediate connector C-23 and the convertible top control module connector D-45.

STEP 4. Check the CAN bus lines inside the convertible top control module. Measure the resistance at convertible top control module connector D-45.




1. Disconnect convertible top control module connector D-45, and measure the resistance at the component side of convertible top control module connector D-45.




2. Measure the resistance between convertible top control module connector D-45 (terminals 48 and 37).

OK: 2 ohms or less




3. Measure the resistance between convertible top control module connector D-45 (terminals 49 and 38).

OK: 2 ohms or less

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

YES: Go to Step 5.

NO: Replace the convertible top control module.

STEP 5. Check the terminator resistor inside the ECM or PCM . Measure the resistance at ECM or PCM connector B-18.

1. Disconnect ECM or PCM connector B-18, and measure the resistance at the component side of ECM or PCM connector B-18.

2. Measure the resistance between ECM or PCM connector terminals 17 and 18.

OK: 120 ± 20 ohms

Q: Does the resistance measure 120 ± 20 ohms?

YES: Intermittent malfunction.

NO: Replace the ECM or PCM . When the ECM or PCM is replaced, register the encrypted code. Refer to Chassis Electrical - Encrypted Code Registration Criteria Table.