System Readiness Test Status

Purpose
The Readiness function also referred as I/M Readiness or I/M Flags indicate if a full diagnostic check has been "Completed" (is "Ready") for each non-continuous monitor. Enhanced I/M State Emission Programs will use the Readiness status (Codes) to see if the vehicle is ready for OBD II testing. "Incomplete" (Not Ready) codes will be one of the triggers for I/M failure.

Overview
The engine control module (ECM) or powertrain control module (PCM) monitors the following main diagnosis items and records whether the evaluation was completed or is incomplete. The Readiness Codes are established for the I/M programs, thereby confirming that the vehicles have not been tampered with by erasing the diagnostic trouble code(s) (DTCs) before I/M testing. The Readiness Codes and DTCs can be reset by disconnecting the battery or by erasing the codes with a scan tool MB991958 (MUT-III sub assembly). For this reason, all the Readiness Codes must be displayed "Complete" before I/ M testing. When the monitors run and complete, the scan tool MB991958 (MUT-III sub assembly) will display the Readiness Codes as "Complete" (General Scan Tools display as "Ready"). When the vehicle is operating normally and the OBD-II Drive Cycle is carried out, the Readiness Codes will be set as "Complete" on the first drive cycle. For DTCs requiring two drive cycles to detect a fault, the second drive cycle is required to set the Readiness Codes as "Complete" if a fault is detected during the first drive cycle. If the fault is still there after the second drive cycle, a DTC will be set.

- Catalyst: P0421, P0431
- Evaporative system: P0441, P0442, P0455, P0456
- Heated oxygen sensor: P0130, P0131, P0132, P0133, P0134, P0136, P0137, P0138, P0139, P0150, P0151, P0152, P0153, P0154, P0156, P0157, P0158, P0159
- Heated oxygen sensor heater: P0135, P0141, P0155, P0161
- EGR system: P0401

After all the Readiness Codes are displayed as "Complete", the technician is assured that any DTCs related to the monitor will be displayed if the system has a problem. That is why some State's I/M programs require the Readiness Code as "Complete" before they check for DTCs.

NOTE: After a repair is made for a DTC, the technician should drive the OBD-II Drive Cycle checking that the scan tool MB991958 (MUT-III Sub Assembly) displays all the Readiness Codes as "Complete".