Description & Operation

A drive cycle is a pattern of driving in which the PCM will execute all OBD-II diagnostic monitors. A drive cycle can be used to cause a fault to set or to verify a fault will not return after a repair has been done.

The drive cycle consists of 3 modes. In Mode 1, the PCM learns air/fuel ratio, idle speed and other driveability characteristics. This information is called the fuel table. Fuel table information is stored in the PCM in Keep Alive Memory (KAM). KAM will lose all information if battery runs down or is disconnected. Use drive cycle Mode 1 to restore KAM memory.

Mode 2 drive cycle exercises the EGR and fuel system diagnostic monitors. Mode 3 drive cycle exercises oxygen sensor and catalyst diagnostic monitors. Before performing Modes 2 and 3, ensure Mode 1 drive cycle has been completed or testing results may be incorrect.

To verify that all 3 Modes have been successfully completed, access DTCs. If a DTC P1000 is received, all drive cycles have not been successfully completed. See CIRCUIT TEST QC.

DTC P1000 could be caused by drive cycle not properly performed or a mechanical or electrical fault in the vehicle. The completion of Modes 2 and 3 can be verified by checking diagnostic monitors on scan tool. See ON-BOARD SYSTEM READINESS (OSR) TEST MODE  under ADDITIONAL SYSTEM FEATURES.