On Board Diagnostic (OBD), function
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The electronic anti-theft immobilizer has extensive On Board Diagnostic (OBD) capabilities. If malfunctions occur in any of the system components, corresponding Diagnostic Trouble Codes (DTC) are stored in the DTC memory of the anti-theft immobilizer.
Before performing any troubleshooting or inspection, always begin by checking for DTCs using the On Board Diagnostic (OBD) program. DTCs stored in memory are retrieved/checked with VAG 1551 scan tool or VAS 5051 in mode "Self Diagnosis". See ANTI-THEFT IMMOBILIZER, ON BOARD DIAGNOSTIC .
Where applicable, also use VAS 5051 tester in mode "Guided Fault Finding".