For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provide an overview of each diagnostic category.

### Description

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 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 requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a diagnostic trouble code (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:

• | The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.

• | 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 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:

• | The air conditioning system

• | The catalytic converter efficiency

• | Comprehensive component monitoring--Emission related inputs and outputs

• | The evaporative emission (EVAP) system

• | The fuel delivery system

• | Heated catalyst monitoring

• | Misfire monitoring

• | The oxygen sensor system (O2S or HO2S)

• | The oxygen sensor heater system (HO2S heater)

For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table. Systems such as fuel delivery, 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.

### Diagnostic Aids

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.

### Circuit/System Verification

Review the I/M System Status indicators. All I/M System Status indicators should report YES.

### Circuit/System Testing

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 Engine DTC information with a scan tool. Verify no DTC is set that would prevent the I/M System Status tests from completing.

⇒ | If a DTC is set, diagnose that DTC before continuing. Refer to Inspection/Maintenance (I/M) System DTC Table.

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 (I/M) Complete System Set Procedure.

3. Observe the scan tool I/M System Status parameters. Verify the I/M System Status parameters report YES.

⇒ | If any I/M System Status parameters report NO, perform the Inspection/Maintenance (I/M) Complete System Set Procedure.