Inspection Procedure 1
Communication with Scan Tool MB991958 is Impossible.Immobilizer-ECU Power Supply, Ground and ECM <M/T> or PCM <A/T> Communication Line Circuit Part 1:
Immobilizer-ECU Power Supply, Ground and ECM <M/T> or PCM <A/T> Communication Line Circuit Part 2:
Communication with scan tool MB991958 is impossible
Immobilizer-ECU is energized when the ignition switch is turned "ON," and the MFI relay is turned on. The ECM
TECHNICAL DESCRIPTION (COMMENT)
- This malfunction may be caused by a defective immobilizer-ECU, ECM
- If the MFI system is normal, the MFI relay can be determined as normal. In addition, if the MFI system and scan tool MB991958 can communicate each other, the circuits between the data link connector and the ECM
NOTE: If this malfunction appears, MFI system DTC P0513 will be output.
TROUBLESHOOTING HINTS
- Malfunction of immobilizer-ECU
- Malfunction of ECM
- Damaged wiring harness or connectors
DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991911: Main Harness B (Vehicles without CAN communication system)
STEP 1. Using scan toll MB991958, read the MFI system diagnostic trouble code.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool.
Use scan tool MB991958 to confirm the MFI system DTC.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch "ON" to position.
3. Read the MFI system diagnosis code.
Q: Can scan tool MB991958 communicate with the MFI system? Is an MFI system DTC other than P0513 output?
YES: Go to Step 2.
NO: Refer to MFI Diagnostics. Diagnostic Strategies
STEP 2. Check the immobilizer-ECU power supply circuit by backprobing.
1. Do not disconnect immobilizer-ECU connector C-79.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 7 and ground by backprobing.
- The measured value should be approximately 12 volts (battery positive voltage).
Q: Does the measured voltage correspond with this range?
YES: Go to Step 5.
NO: Go to Step 3.
STEP 3. Check immobilizer-ECU connector C-79 and MFI relay connector A-18X for damage.
Q: Are immobilizer-ECU connector C-79 and MFI relay connector A-18X damaged?
YES: Repair or replace the connector. Refer to Harness Connector Inspection. Confirm that scan tool MB991958 communicates normally.
NO: Go to Step 4.
STEP 4. Check the wiring harness between immobilizer-ECU connector C-79 (terminal 7) and MFI relay connector A-18X (terminal 4).
NOTE: After checking intermediate connector C-28,check the wires. If intermediate connector C-28 is damaged, repair or replace the wiring harness. Refer to Harness Connector Inspection.
Q: Are the wiring harness between immobilizer-ECU connector C-79 (terminal 7)and MFI relay connector A-18X (terminal 4)damaged?
YES: Replace the wiring harness. Confirm that scan tool MB991958 communicates normally.
NO: There is no action to be taken.
STEP 5. Check the immobilizer-ECU ground circuit by backprobing.
1. Do not disconnect immobilizer-ECU connector C-79.
2. Measure the resistance between terminal 3 and ground by backprobing.
- The measured value should be 2 ohm or less.
Q: Does the measured resistance value correspond with this range?
YES: Go to Step 6.
NO: Go to Step 8.
STEP 6. Check immobilizer-ECU connector C-79 for damage.
Q: Is immobilizer-ECU connector C-79 in good condition?
YES: Go to Step 7.
NO: Repair or replace the connector. Refer to Harness Connector Inspection. Confirm that scan tool MB991958 communicates normally.
STEP 7. Check the wiring harness between immobilizer-ECU connector C-79 (terminal 3) and ground.
Q: Is the wiring harness between immobilizer-ECU connector C-79 (terminal 3) and ground damaged?
YES: Repair the wiring harness. Confirm that scan tool MB991958 communicates normally.
NO: There is no action to be taken.
STEP 8. Check the wiring harness between immobilizer-ECU connector C-79 (terminal 5) and ECM connector C-56 (terminal 51) <2.4L M/T>, C-62 (terminal 98) <3.0L M/T> or PCM connector C-61 (terminal 111) <2.4L A/T>, C-63 (terminal 111) <3.0L A/T>.
Q: Are the wiring harness between immobilizer-ECU connector C-79 and ECM connector C-56 (terminal 51) <2.4L M/T>, C-62 (terminal 98) <3.0L M/T> or PCM connector C-61 (terminal 111) <2.4L A/T>, C-63 (terminal 111) <3.0L A/T> damaged?
YES: Repair the wiring harness. Confirm that scan tool MB991958 communicates normally.
NO: Go to Step 9.
STEP 9. Replace the immobilizer-ECU.
Q: Did the communication with MUT-II become possible after replacing the immobilizer-ECU?
YES: Register the password (secret code) and encrypted code (Refer to How To Register Encrypted Code). Confirm that scan tool MB991958 communicates normally.
NO: Go to Step 10.
STEP 10. Recheck for malfunction
Q: Is a malfunction eliminated?
YES: Go to Step 11.
NO: Replace the immobilizer-ECU.
STEP 11. Replace the ECM
Q:
YES: Register the password (secret code) and encrypted code (Refer to How To Register Encrypted Code). Confirm that scan tool MB991958 communicates normally.
NO: Go to Step 12.
STEP 12. Recheck for malfunction
Q: Is a malfunction eliminated?
YES: This diagnosis is complete. (If no malfunction are not found in all steps, an intermittent malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.)
NO: Replace the ECM