Inspection Procedure 1

Immobilizer-ECU Power Supply, Ground And ECM <M/T> Or PCM <A/T> Communication Line Circuit:

Connectors:

CIRCUIT OPERATION
Immobilizer-ECU is energized when the ignition switch is turned "ON," and the MFI relay is turned on.

The ECM or PCM 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, ECM or PCM , or a defect in the communication line between the immobilizer-ECU and ECM or PCM . 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 ECM or PCM can determined as normal.

NOTE: If this malfunction appears, MFI system DTC P1610 will be output.

TROUBLESHOOTING HINTS
- Malfunction of immobilizer-ECU
- Malfunction of ECM or PCM
- Damaged harness wires or connectors

DIAGNOSIS
Required Special Tools:
MB991223: Harness Set
MB991502: Scan Tool (MUT-II)

STEP 1. Can scan tool MB991502 communicate with the MFI system? Does MFI system DTC other than P1610 reset?
If scan toot MB991502 cannot communicate with the MFI system, or a MFI system DTC other than P1610 resets, refer to Diagnosis (Computers/Testing).
If scan tool MB991502 can communicate with the MFI system, and a DTC other than P1610 resets, go to Step 2.

STEP 2. Check the immobilizer-ECU power supply circuit.
1. Disconnect immobilizer-ECU connector C-79 and measure at the harness side.
2. Turn the ignition switch "ON" position.
3. Voltage between terminal 7 and ground.
- Voltage should be approximately 12 volts (battery positive voltage).
If not approximately 12 volts, go to Step 3. If approximately 12 volts, go to Step 5.

STEP 3. Check immobilizer-ECU connector C-79 and MFI relay connector A-21X for damage.
If immobilizer-ECU connector C-79 and MFI relay connector A-21X are damaged, repair or replace them. Refer to Harness Connector Inspection.
Confirm that scan tool MB991502 communicates normally.
If these connectors are in good condition, go to Step 4

STEP 4. Check the harness wires between immobilizer-ECU connector C-79 and MFI relay connector A-21X.

NOTE: After checking intermediate connector C-28, check the wires. If intermediate connector C-28 is damaged, repair or replace it. Refer to Harness Connector Inspection.

If the harness wires between immobilizer-ECU connector C-79 and MFI relay connector A-21X are damaged, repair them. Confirm that scan tool MB991502 communicates normally.

STEP 5. Check the immobilizer-ECU ground circuit.
1. Disconnect immobilizer-ECU connector C-79 and measure at the harness side.
2. Resistance between terminal 3 and ground.
- Should be less than 2 Ohms.
If open circuit, go to Step 6.
If less than 2 Ohms, go to Step 8.

STEP 6. Check immobilizer-ECU connector C-79 for damage.
If immobilizer-ECU connector C-79 is damaged, repair or replace it. Refer to Harness Connector Inspection.
Confirm that scan tool MB991502 communicates normally.
If the connector is in good condition, go to Step 6.

STEP 7. Check the harness wire between immobilizer-ECU connector C-79 and ground.
If the harness wire between immobilizer-ECU connector C-79 and ground is damaged, repair it.
Confirm that scan tool MB991502 communicates normally.

STEP 6. Check the harness wires between immobilizer-ECU connector C-79 and ECM or PCM connector.

NOTE: The ECM or PCM connector indicates the following connectors:
- 2.4L engine-M/T ECM connector C-56
- 2.4L engine-A/T: PCM connector C-61
- 3.0L engine-M/T; ECM connector C-62
- 3.0L engine-A/T: PCM connector C-63

If the harness wires between immobilizer-ECU connector C-79 and ECM or PCM connector are damaged, repair them.
Confirm that scan tool MB991502 communicates normally. If the harness wires are in good condition, go to Step 7.

STEP 7. Replace the immobilizer-ECU or ECM or PCM .

CAUTION: Do not register the immobilizer-ECU at this stage, otherwise the immobilizer-ECU must be replaced with new one again if ECM or PCM is replaced due to a malfunction.

1. Replace the immobilizer-ECU.
2. Can scan tool MB991502 communicate with the immobilizer system? If no, replace the ECM or PCM and ignition key.
3. Register the password (secret code) and encrypted code.
Confirm that scan tool MB991502 communicates normally.