Description
Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the I/M emission inspection in order to renew license plates. This is accomplished by viewing the I/M System Status display on a scan tool. Using a scan tool, the technician can observe the I/M System Status in order to verify that the vehicle meets the criteria that complies with the local area requirements.
Conditions for Updating the I/M System Status
Each system monitor requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a DTC. A system monitor completes when either all DTCs comprising the monitor have run and passed, or any DTC comprising the monitor has illuminated the malfunction indicator lamp (MIL). Once the monitor completes, the I/M System Status display will indicate YES in the Completed column. For example, when the Misfire Monitoring System Status display indicates YES, all of the misfire components have been diagnosed. The I/M System Status will indicate NO in the Completed column when any of the required DTCs for that system have not run. The following is a list of conditions that would set the I/M System Status indicators to NO:
| • | The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the system monitor. |
| • | The battery has been disconnected or discharged below operating voltage. |
| • | The control module power or ground has been interrupted. |
| • | The control module has been reprogrammed. |
| • | The control module DTCs have been cleared as part of a service procedure. |
Monitored Emission Control Systems
The OBD II System monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following:
| • | Comprehensive component monitoring -- Emission related inputs and outputs |
| • | EGR system |
| • | Misfire monitoring |
For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table .
Step | Action | Yes | No |
|---|---|---|---|
1 |
Important: Any DTCs set, even those not listed in the Inspection/Maintenance system DTC table, may prevent the required DTCs from running. Did you find and repair a DTC or driveability concern? | Go to Step 3 | Go to Step 2 |
2 |
Was a reprogramming or repair service required? | Go to Inspection/Maintenance (I/M) Complete System Set Procedure | Go to Step 3 |
3 | Observe the I/M System Status display, with a scan tool. Is more than one system indicating a NO status? | Go to Inspection/Maintenance (I/M) Complete System Set Procedure | Go to the I/M System Set Procedure for the indicated system that did not update to YES |
