DTC P1638: Immobilizer Information Mismatched: Troubleshooting

Step	Action	Yes	No
1	Diagnostic Trouble Code (DTC) confirmation Clear DTC(s) referring to DTC CLEARANCE . Turn the ignition switch to OFF position. Check if any DTC is detected referring to DTC CHECK . Is DTC P1638 still detected?	Go to Step 2.	The troubleshooting is completed.
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 . Is DTC P1638 still detected?	Go to Step 3.	The troubleshooting is completed.
3	Check ECM specification 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?	Go to Step 4.	Replace ECM with the correct one and recheck if DTC P1638 is still detected by ECM.
4	DTC check in ECM Is any DTC other than P1638 detected in Step 1?	Perform the troubleshooting referring to the corresponding flowchart.	Go to Step 5.
5	DTC check in BCM Check BCM for DTC referring to DTC CHECK . Is any DTC detected?	Perform the troubleshooting referring to the corresponding flowchart, refer to BODY ELECTRICAL CONTROL SYSTEM .	Go to Step 6.
6	Replacement of BCM Replace BCM with new one referring to BCM REMOVAL AND INSTALLATION . Check ECM for DTC referring to DTC CHECK . Is DTC P1638 still detected?	Go to Step 7.	The troubleshooting is completed.
7	Replacement of ECM Replace ECM with new one referring to ECM (ENGINE CONTROL MODULE) REMOVAL AND INSTALLATION . Check ECM for DTC referring to DTC CHECK . Is DTC P1638 still detected?	Recheck CAN communication wire circuits and poor connection at ECM, ABS control module and BCM connectors.	The troubleshooting is completed.