DTC P1638: Immobilizer Information Mismatched: Troubleshooting

TROUBLESHOOTING CHART

Step	Action	YES	NO
1	Diagnostic Trouble Code (DTC) confirmation Clear DTC(s) referring to DIAGNOSTIC TROUBLE CODE (DTC) CLEARANCE . Turn the ignition switch to OFF position. Check if any DTC is detected referring to DIAGNOSTIC TROUBLE CODE (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 DIAGNOSTIC TROUBLE CODE (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 2.	Replace ECM with the correct one and recheck if DTC P1638 is still detected by ECM.
4	Diagnostic Trouble Code (DTC) check in ECM Is any DTC other than P1638 detected in Step 1?	Perform the troubleshooting. Refer to appropriate DTC diagnostics.	Go to Step 3.
5	Diagnostic Trouble Code (DTC) check in BCM Check BCM for DTC referring to NO DTC DETECTION AFTER PERFORMING DTC CHECK . Is any DTC detected?	Perform the troubleshooting. Refer to appropriate DTC diagnostics.	Go to Step 5.
6	Replacement of BCM Replace BCM with new one referring to BCM REMOVAL AND INSTALLATION . Check ECM for DTC referring to DIAGNOSTIC TROUBLE CODE (DTC) CHECK . Is DTC P1638 still detected?	Go to Step 6.	The troubleshooting is completed.
7	Replacement of ECM Replace ECM with new one referring to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION . Check ECM for DTC referring to DIAGNOSTIC TROUBLE CODE (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.