The following procedure is designed to satisfy the enable criteria necessary to execute all of the I/M readiness diagnostics, and complete the trips for those particular diagnostics. When all diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform this test when more than one or all of the I/M System Status indicators are set to NO.
Rough road conditions may prevent some of the tests from running. Extreme high or low ambient temperatures may prevent tests such as Heated Oxygen Sensor (HO2S) heater and Evaporative Emission (EVAP) system from initiating. If a step is interrupted before completion, perform the remaining portion of the set procedures. Any portion of the set procedure that requires the engine at operating temperature may be repeated. This allows most of the diagnostics to run and the remaining tests can be performed using the individual System Set Procedures.
If the vehicle has recently run, start the Drive Cycle Procedure at step 3. This will allow the tests that require the engine at operating temperature to run. Using this method allows shorter cool down periods if the tests requiring a cold start do not initiate.
The scan tool can be used to monitor each of the I/M System Status indicators during the Drive Cycle Procedure. When all of the indicators for a test step have updated to YES, testing can move on to the next step even if the remaining portion of the test is not complete. For example, step 3 is designed to run the Evaporative Emission (EVAP), Secondary Air Injection (AIR), and Heated Oxygen Sensor (HO2S) tests. The procedure instructs the technician to operate the vehicle in the enable conditions for 6 minutes. If all 3 tests have updated to YES within 4 minutes, it is not necessary to continue with the enable conditions and testing can advance to the next step.
NOTE: It may not be necessary to meet all conditions below to enable specific monitors to run an individual diagnostic test. For more information on enable conditions for running specific monitors, see SELF DIAGNOSTIC SYSTEM in appropriate SELF DIAGNOSTICS article.
Barometric Pressure (BARO) is greater than 74 kPa.
Engine Coolant Temperature (ECT) is less than 75 F (24 C).
Intake Air Temperature (IAT) is less than 75 F (24 C).
The difference between the IAT and the ECT is 11 F (6 C) or less.
The battery voltage is 9-18 volts.
The fuel level is between 1/4 and 3/4.
Inspection/Maintenance (I/M) System Check
Any DTCs set may prevent the required monitors from running. In most cases, anytime a control module is reprogrammed or the DTCs are cleared as part of a repair procedure, all the I/M system status indicators will reset to NO. Prior to performing Drive Cycle Procedure (Inspection/Maintenance Complete System Set Procedure), perform Inspection/Maintenance System Check. See Fig. 1.
Fig. 1: Inspection/Maintenance System Check (2001-03 GM Vehicles - Except Metro, Firefly (Canadian), Prizm, Saturn & Tracker)
Courtesy of GENERAL MOTORS CORP.
Inspection/Maintenance (I/M) Complete System Set Procedure
The step numbers below refer to the step numbers in Fig. 2 on 2001-03 GM vehicles, except Metro, Firefly (Canadian), Prizm, Saturn & Tracker.
Ensure you perform Inspection/Maintenance (I/M) System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
This step is to run the HO2S Heater Tests and initiate the EVAP System Test. Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria. The Engine Control Module (ECM) considers the engine to be cold if the following conditions are met: ECT less than 95 F (35 C), ECT and IAT are within 11 F (6 C) of each other at start up.
This step is to run the EVAP, AIR and the Oxygen Sensor Tests. The EVAP Test begins once the engine coolant reaches a calibrated temperature. The AIR Test, if equipped, begins shortly after Closed Loop and the indicated speed is achieved. The Oxygen Sensor Tests begin once the engine is at operating temperature, in Closed Loop fuel control, and a calibrated amount of time has elapsed.
This step is to run the Exhaust Gas Recirculation (EGR) Tests. The EGR Tests are run during a gradual deceleration with a closed throttle. The vehicle speed is required in order to maintain a high, steady Manifold Absolute Pressure (MAP) signal.
This step is to run the Catalyst Tests. This test runs during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
Perform the individual system test for any of the systems that do not update to YES.
The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis. See appropriate SELF DIAGNOSTICS article.
Tuesday, March 29th, 2011 AT 10:46 PM