On-Board Diagnostics (OBD-II)

Federal Test Procedure (FTP) sets maximum allowable emission standards. A Malfunction Indicator Light (MIL) must illuminate if a system or component either fails or deteriorates to a point where the vehicle emissions could increase to more than 1 1/2 times FTP standards. Self-diagnostic system is used to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring efficiency of emission control system, and improving diagnosis and repair when system failures occur. Engine Control Module (ECM) monitors engine operation and contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTC) and complies to On-Board Diagnostics Generation II (OBD-II) standards.

If malfunction does not reoccur in 3 consecutive trips, MIL goes off, but DTCs remain recorded in ECM memory. DTCs may only be retrieved using an On-Board Diagnostic-II (OBD-II) scan tool that complies with SAE standard J-1978 or Volvo hand-held tester connected to Data Link Connector (DLC). See Figure. Scan tool also provides freeze frame data and can be used to clear DTCs.

To properly diagnose vehicle, vehicle manufacturer recommends use of Volvo Scan Tool. Generic scan tools may not be capable of performing all diagnostic functions. See DIAGNOSTIC FUNCTIONS . All voltage tests should be performed with a Digital Volt-DVOM (DVOM) with a minimum 10-megaohm input impedance, unless specifically stated differently in testing procedures. Ensure ignition switch is in OFF position when performing resistance tests.