I/M Readiness
The readiness function is implemented based on the SAE J1979/ISO 15031-5 format. Clearing codes using a scan tool results in the various I/M readiness bits being set to a "not-ready" condition. As each non-continuous monitor completes a full diagnostic check, the I/M readiness bit associated with that monitor is set to a "ready" condition. This may take one or two driving cycles based on whether malfunctions are detected or not. The readiness bits for comprehensive component monitoring and misfire monitoring are immediately considered complete since they are continuous monitors. Because the evaporative system monitor requires ambient conditions between 40 and 100 oF and BARO > 22.5 " Hg (< 8,000 ft.) to run, special logic can "bypass" the running the evap monitor for purposes of clearing the evap system I/M readiness bit due to the continued presence of these extreme conditions. The table below shows which monitors must complete for I/M readiness.
| I/M Readiness Bit | Bank 1 | Bank 2 |
| Catalyst monitoring | P0420 | P0430 |
| Heated catalyst monitoring | Not Supported | Not Supported |
| Evaporative system monitoring (0.040"/0.150" monitor used for I/M readiness) |
P0442 (0.040") P0455 (0.150 for HD OBD) |
|
| Secondary air system monitoring | P0491/P0410/P2448 | P0492/P2449 |
| Oxygen sensor monitoring | ||
| Upstream response test | P0133 | P0153 |
| Upstream lack of movement test | P2195/P2196 | P2197/P2198 |
| Upstream heater | P0053/P0030 | P0059/P0050 |
| Downstream functional test | P0136/P2270/P2271 | P0156/P2272/P2273 |
| Downstream heater | P0054/P00D2 | P0060/P00D4 |
| Downstream response test | P013A/P013E | P013C/P014A |
| Post catalyst fuel trim monitor | P2096/P0297 | P013C/P014A |
| Oxygen sensor heater monitoring | Same as O2 sensor above | Same as O2 sensor above |
| EGR and/or VVT system monitoring | ||
| Stepper Motor EGR DPFE EGR |
P0400 P1405/P1406/P0401/P0402 |
|
| VVT supported | P0011/P0012/P0014/P0015 | P0021/P0022/P0024/P0025 |
| Misfire monitoring | Always ready | Always ready |
| Fuel system monitoring | Fuel trim always ready | Fuel trim always ready |
| A/F ratio imbalance monitor | P219A | P219B |
| Comprehensive component monitoring | Always ready | Always ready |
Evap bypass logic for new 1999 MY, 2000 MY, and beyond vehicles:
If the evaporative system monitor conditions are met with the exception of the 40 to 100 °F ambient temperatures or BARO range, a timer is incremented. The timer value is representative of conditions where the Evap monitor could have run (all entry conditions met except IAT and BARO) but did not run due to the presence of those extreme conditions. If the timer continuously exceeds 30 seconds during a driving cycle in which all continuous and non-continuous monitors were evaluated, the evaporative system monitor is then considered complete. If the above conditions are repeated during a second driving cycle, the I/M readiness bit for the evaporative system is set to a "ready" condition.
Power Take Off Mode
While PTO mode is engaged, the I/M readiness bits are set to a "not-ready" condition. When PTO mode is disengaged, the I/M readiness bits are restored to their previous states prior to PTO engagement. During PTO mode, only CCM circuit checks continue to be performed.