Monitored Emission Control Systems

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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 toInspection/Maintenance (I/M) System DTC Table .

Inspection/Maintenance (I/M) System Check

Step	Action	Yes	No
1	Perform the Diagnostic System Check - Engine Controls . IMPORTANT: Any DTCs set, even those not listed in the Inspection/Maintenance system DTC table, may prevent the required DTCs from running. Repair any DTCs or driveability concerns. Did you find and repair a DTC or driveability concern?	Go to Step 3	Go toStep 2
2	Review any service bulletins for software updates that may prevent the required DTCs from running. Perform any reprogramming or repairs indicated by the service bulletins. 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