Chevrolet Equinox Service Manual: Inspection/Maintenance System Check Engine Control

Diagnostic InstructionsPerform theDiagnostic System Check - Vehicleprior to using thisdiagnostic procedure.ReviewStrategy Based Diagnosisfor an overview of thediagnostic approach.Diagnostic Procedure Instructionsprovides an overview ofeach diagnostic category.Description

Several states require that a vehicle pass on-boarddiagnostic (OBD) system tests and the inspection/maintenance (I/M)emission inspection in order to renew license plates. This isaccomplished by viewing the I/M System Status display on a scantool. Using a scan tool, the technician can observe the I/M SystemStatus in order to verify that the vehicle meets the criteria thatcomplies with the local area requirements. While testing in the I/MSystem Status mode, some DTCs may occur that are called I/M TestDTCs. An I/M Test DTC is defined as a fault code that is currentlycommanding the MIL ON, and is stored in non-volatilememory. The intended use of this data is to prevent vehicles frompassing I/M inspection without proper repair to the vehicle. Thesefault codes are not erasable from any scan tool command or erasableby disconnecting power to the controller. The I/M Test DTCs will besupported by all emissions related ECUs such as ECMs, TCMs, FPCMs,etc. An I/M Test DTC will not be stored or erased from the ECUexcept at the end of trip processing which occurs 5-safter ignition OFF.

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 adiagnostic trouble code (DTC). A system monitor is complete wheneither all of the DTCs comprising the monitor have Run and Passed,or any one of the DTCs comprising the monitor have illuminated themalfunction indicator lamp (MIL) . Once all of the tests arecompleted, the I/M System Status display will indicate YES in theCompleted column.

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

The vehicle is new from the factory and has not yet beendriven through the necessary drive conditions to complete thetests.The battery has been disconnected or discharged belowoperating voltage.The control module power or ground has beeninterrupted.The control module has been reprogrammed.The control module DTCs have been cleared as part of aservice procedure.Conditions for Clearing I/M Test DTCsOnly the OBD-II System can erase the I/M Test DTC.The OBD-II system must determine that the malfunctionthat caused the I/M Test DTC to be stored is no longer present andis not commanding the MIL. Each of the following represents ways toclear an I/M Test DTC:If the MIL goes out due to 3-passing drive cycles,scan tool code clear is not used, the I/M Test DTC is erased atpower down of the last drive cycle.If a scan tool code clear is used to turn OFF the MIL, theI/M Test DTC is not erased, the DTC must PASS and not FAIL. The I/MTest DTC is erased at power down of the drive cycle.If the controller is reflashed/reprogrammed, all I/M TestDTCs are erased.For the OBD-II System to run a single drive cyclefor clearing an I/M Test DTC, all of the following conditions mustoccur:Cumulative time of engine run time is greater than600-s.Cumulative vehicle operation above 40-km/h(25-mph) for over 300-s.Continuous vehicle idle for greater than30-s.Turn ignition OFF for 5-s and allow the code toclear.Monitored Emission Control Systems

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

The air conditioning systemThe catalytic converter efficiencyComprehensive component monitoring—Emission relatedinputs and outputsThe evaporative emission (EVAP) systemThe fuel delivery systemHeated catalyst monitoringMisfire monitoringThe oxygen sensor system (O2S or HO2S)The oxygen sensor heater system (HO2S heater)

For the specific DTCs required for each system, refer toInspection/Maintenance (I/M) System DTC Table. Systems such as misfireand comprehensive components may not be listed in a system statuslist. These tests run continuously and do not require an I/M SystemStatus indicator.

Diagnostic Aids

The I/M System Status display provides an indication of whenthe control module has completed the required tests. This does notnecessarily mean that the test has passed, only that a decision wasmade. If the diagnostic fails, a DTC will indicate the failure. Ifa failure indication is present for a DTC associated with one ofthe I/M regulated systems, it may prevent other required tests fromrunning. For example, a DTC for the control circuit of the EVAPpurge solenoid may not be listed in the Inspection/MaintenanceSystem DTC Table because it is a continuous test. If this DTC isset, the Active Tests for the EVAP system may not run.

The I/M System Status information may be useful for atechnician to determine if diagnostics have run when verifyingrepairs.

Circuit/System Verification

Review the I/M System Status indicators. All I/M SystemStatus indicators should report YES, and no I/M Test DTCs should bepresent.

Circuit/System Testing

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

Observe the Engine DTC information with a scan tool. Verifyno DTCs are present.If a DTC is set that would prevent the I/M System Statustests from completing, diagnose that DTC before continuing. RefertoDiagnostic Trouble Code (DTC) List - Vehicle.Review applicable service bulletins for software updates thatwould prevent the I/M System Status tests from completing.If a control module re-program or other repair isrequired, perform theInspection/Maintenance Complete System Set Procedure.Observe the I/M System Status indicators.If any I/M System Status indicators report NO, perform theInspection/Maintenance Complete System Set Procedure.Observe the I/M Test DTC information with a scan tool. Verifythere are no I/M Test DTCs present.If an I/M Test DTC is set and all of the I/M System Statusindicators are Yes, there is no need to perform the Complete SystemSet Procedure. Diagnose the DTC using theDiagnostic Trouble Code (DTC) List - Vehicleand refer to Conditions forClearing the I/M Test DTCs.If an I/M Test DTC is set and the I/M System Statusindicators are NO, diagnosis the DTC and perform theInspection/Maintenance Complete System Set Procedure.