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Inspection/Maintenance System Check

Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the inspection/maintenance (I/M) emission inspection in order to renew number 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. While testing in the I/M System Status mode, some diagnostic trouble codes (DTCs) may occur that are called I/M Test DTCs. An I/M Test DTC is defined as a DTC that is currently commanding the MIL ON, and is stored in non-volatile memory. The intended use of this data is to prevent vehicles from passing I/M inspection without proper repair to the vehicle. These DTCs are not erasable from any scan tool command or erasable by disconnecting power to the controller. The I/M Test DTCs will be supported by all emissions related control modules. For example, Engine Control Modules (ECMs), Transmission Control Modules (TCMs), and Fuel Pump Control Modules (FPCMs). An I/M Test DTC will not be stored or erased from the control module except at the end of trip processing which occurs 5 s after vehicle OFF.

Each system requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a DTC. A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed, or any one of the DTCs comprising the monitor have illuminated the malfunction indicator lamp (MIL). Once all of the tests are completed, the I/M System Status display will indicate YES in the Completed column.

For example, when the HO2S Heater Status indicates YES, either all of the oxygen sensor heater tests have passed or one of the tests has illuminated the MIL. If the vehicle has four heated oxygen sensors, either all four heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO:

1. Only the OBD II System can erase the I/M Test DTC. The OBD II system must determine that the malfunction that caused the I/M Test DTC to be stored is no longer present and is not commanding the MIL. Each of the following represents ways to clear an I/M Test DTC:

•	If the MIL goes out due to 3 passing drive cycles and the scan tool code clear is not used, the I/M Test DTC is erased at power down of the last drive cycle.

•	If a scan tool code clear is used to turn OFF the MIL, the I/M Test DTC is not erased, the DTC must PASS and not FAIL. The I/M Test DTC is erased at power down of the drive cycle.

•	If the controller is reflashed/reprogrammed, all I/M Test DTCs are erased.

2. For the OBD II System to run a single drive cycle for clearing an I/M Test DTC, all of the following conditions must occur:

•	Vehicle ON, engine run time is greater than 600 s.

•	Cumulative vehicle speed is greater than 41 km/h (25 mph) for greater than 300 s.

•	Continuous engine running, and vehicle speed is 0 km/h (0 mph) for greater than 30 s.

•	Vehicle OFF for 5 s.

The OBD II system monitors all emission control systems that are on-board. Not all vehicles need every possible emission control system. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following; if equipped:

For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) Test DTC Table . Systems such as misfire and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.

The I/M System Status display provides an indication of when the control module has completed the required tests. This does not necessarily mean that the test has passed, only that a decision was made. If the diagnostic fails, a DTC will indicate the failure. If a failure indication is present for a DTC associated with one of the I/M regulated systems, it may prevent other required tests from running. For example, a DTC for the control circuit of the EVAP purge solenoid may not be listed in the Inspection/Maintenance System DTC Table because it is a continuous test. If this DTC is set, the Active Tests for the EVAP system may not run.

The I/M System Status information may be useful for a technician to determine if diagnostics have run when verifying repairs.

Vehicle in Service Mode, observe the scan tool I/M System Status indicators, and the I/M Test DTCs. All I/M System Status indicators should display YES, and no I/M Test DTCs should be present.

Note: Many DTC related repairs will instruct the technician to clear the DTC information. Clearing the DTC will reset the I/M System Status indicators to NO. Performing the I/M Complete System Set Procedure will set each of the I/M System Status indicators to YES.

1. Observe the ECM DTC information with a scan tool. Verify no DTCs are present.

⇒	If a DTC is set that would prevent the I/M System Status tests from completing, diagnose that DTC before continuing. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Review applicable service bulletins for software updates that would prevent the I/M System Status tests from completing.

⇒	If a control module re-program or other repair is required, perform the Inspection/Maintenance Complete System Set Procedure .

3. Observe the scan tool I/M System Status indicators. The I/M System Status indicators should display Yes.

⇒	If any I/M System Status indicators display NO, perform the Inspection/Maintenance Complete System Set Procedure .

4. Observe the I/M Test DTC and I/M System Status information with a scan tool. There should be no I/M Test DTCs, and there should be no I/M System Status indicators displaying NO.

⇒	If an I/M Test DTC is set and all of the I/M System Status indicators are Yes, there is no need to perform the Complete System Set Procedure. Diagnose the DTC using the Diagnostic Trouble Code (DTC) List - Vehicle and refer to Conditions for Clearing the I/M Test DTCs.

⇒	If an I/M Test DTC is set and the I/M System Status indicators are NO, diagnosis the DTC and perform the Inspection/Maintenance Complete System Set Procedure .