Inspection Procedure 1
Communication with Scan Tool MB991502 is ImpossibleImmobilizer-ECU Power Supply, Ground And PCM Communication Line Circuit:
Connector:
CIRCUIT OPERATION
Immobilizer-ECU is energized when the ignition switch is turned "ON", and the engine control relay is turned on. The powertrain control module transmits a signal from scan tool MB991502 to the immobilizer-ECU as it is. In the same way, a signal from the immobilizer-ECU is also transmitted to scan tool MB991502 as it is.
TECHNICAL DESCRIPTION (COMMENT)
- This malfunction may be caused by a defective immobilizer-ECU, powertrain control module, or a defect in the communication line between the immobilizer-ECU and powertrain control module. If this malfunction appears when the MFI system and scan tool MB991502 can communicate each other, MFI system DTC P1610 will reset.
- If the MFI system is normal, the MFI relay can be determined as normal. In addition, if the MFI system and scan tool MB991502 can communicate each other; the circuits between the data link connector and the powertrain control module can determined as normal.
NOTE: If this malfunction appears, MFI system DTC P1610 will be output.
TROUBLESHOOTING HINTS
- Malfunction of immobilizer-ECU
- Malfunction of powertrain control module
- Damaged harness wires or connectors
DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
- MB991502: Scan Tool (MUT-II)
STEP 1. Check that scan tool MB991502 can communicate with the MFI system and that the MFI system DTC other than P1610 resets.
Q: Can scan tool MB991502 communicate with the MFI system? Does MFI system DTC other than P1610 reset?
YES: Go to Step 2.
NO: Refer to Diagnosis.
STEP 2. Check the immobilizer-ECU power supply circuit by backprobing.
1. Do not disconnect immobilizer-ECU connector C-107.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 7 and ground by backprobing.
Q: Is the voltage approximately 12 volts (battery positive voltage)?
YES: Go to Step 5.
NO: Go to Step 3.
STEP 3. Check immobilizer-ECU connector C-107 and engine control relay connector C-59 for damage.
Q: Are immobilizer-ECU connector C-107 and engine control relay connector C-59 damaged?
YES: Repair or replace them. Refer to Harness Connector Inspection. Confirm that scan tool MB991502 communicates normally.
NO: Go to step 4.
STEP 4. Check the harness wires between immobilizer- ECU connector C-107 and MFI relay connector C-59.
NOTE: After checking intermediate connector C-72 and joint connector C-14, check the wires. If intermediate connector C-72 and joint connector C-14 are damaged, repair or replace them. Refer to Harness Connector Inspection.
Q: Are the harness wires between immobilizer-ECU connector C-107 and MFI relay connector C-59 damaged?
YES: Replace them. Confirm that scan tool MB991502 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-107.
2. Measure the resistance between terminal 3 and ground by backprobing.
Q: Is the resistance less than two Ohms?
YES: Go to Step 6.
NO: Go to Step 8.
STEP 6. Check immobilizer-ECU connector C-107 for damage.
Q: Is immobilizer-ECU connector C-107 in good condition?
YES: Go to Step 7.
NO: Repair or replace it. Refer to Harness Connector Inspection. Confirm that scan tool MB991502 communicates normally.
STEP 7. Check the harness wire between immobilizer-ECU connector C-107 and ground.
Q: Is the harness Wire between immobilizer-ECU connector C-107 and ground damaged?
YES: Repair it. Confirm that scan tool MB991502 communicates normally.
NO: There is no action to be taken.
STEP 8. Check the harness wires between immobilizer- ECU connector C-107 and powertrain control module connector C-92.
Q: Are the harness wires between immobilizer-ECU connector C-107 and powertrain control module connector C-92 damaged?
YES: Repair them. Confirm that scan tool MB991502 communicates normally.
NO: Go to Step 9.
STEP 9. Replace the immobilizer-ECU or powertrain control module.
Replace the immobilizer-ECU or powertrain control module.
Q: Did the communication with MUT-II become possible after replacing the immobilizer-ECU or the power train control module?
YES: Register the password (secret code) and encrypted code. Confirm that scan tool MB991502 communicates normally
NO: Go to Step 10.
STEP 10. 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 immobilizer-ECU or powertrain control module.