P1638

DTC P1638: Immobilizer Information Mismatched

Wiring Diagram

Refer to Immobilizer Control System Wiring Circuit Diagram Immobilizer Control System Wiring Circuit Diagram.

DTC Detecting Condition and Trouble Area






Troubleshooting



1.
Was "Immobilizer Control System Check" performed?
YES
Go to Step 2.
NO
Go to Immobilizer Control System Check.

2. Diagnostic Trouble Code (DTC) confirmation

Disconnect negative (-) cable from battery for more than 5 seconds.
Connect negative (-) cable to battery.
Check if any DTC is detected referring to DTC Check DTC Check.

Is DTC P1638 still detected?
YES
Go to Step 3.
NO
Intermittent trouble check for intermittent referring to Intermittent and Poor Connection Inspection.

3. ECM specification check

Check ECM part number to see if ECM is applicable to the vehicle in service.

Is a correct ECM used for the vehicle in service?
YES
Go to Step 4.
NO
Replace ECM with the correct one and recheck if DTC P1638 is still detected by ECM.

4. DTC check of ECM

Check ECM for DTC referring to DTC Check DTC Check.

Is DTC U0073, U0101, U0121, U0140 and/or U0155 detected?
YES
Go to applicable DTC troubleshooting.
NO
Go to Step 5.

5. DTC check of BCM

Check BCM for DTC referring to DTC Check DTC Check.

Is DTC U0073, U0100, U0101, U0144, U0151 and/or U0155 detected?
YES
Go to applicable DTC troubleshooting.
NO
Go to Step 6.

6. CAN communication circuit check

Check for open, short and high resistance in CAN communication circuits between ECM and BCM.

Is each CAN communication circuit in good condition?
YES
Go to Step 7.
NO
Repair circuit.

7. Replacement of BCM

Replace BCM with new one referring to Service and Repair BCM Removal and Installation.
Check ECM for DTC referring to DTC Check DTC Check.

Is DTC P1638 still detected?
YES
Substitute a known-good ECM and recheck.
NO
BCM faulty.