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Inspection Info - Description of the Tests

ASM / Idle Test Procedure

  1. The dynamometer horsepower (hp) setting is determined from a look-up table. Typical values range from 6.0 to 22 hp. The hp calculation is performed by the lane computer and is transmitted to a second PC which controls the dynamometer. The hp setting is applied at the test speed of 40 km/hr (25 mph).
  2. A sample probe(s) is inserted in the tailpipe(s). If the vehicle has dual exhaust, two probes with a "Y" fitting are used such that the sample represents a combination of both exhaust pipes. The system will automatically check for the presence of a combined carbon monoxide(CO) + carbon dioxide(CO2) level of at least six per cent for gasoline vehicles and four per cent for natural gas vehicles. Lower values indicate an exhaust leak or major misfire and the vehicle is rejected. A satisfactory sample may be obtained by using a boot or repositioning the probe to an accessible upstream hole in the tailpipe, provided it is safe to do so. If there is an adequate sample, the analyzers will undergo an auto-zero calibration that resets the zero reading based on the room air in the analyzer enclosure. If the system detects more than 21 ppm hydrocarbon (HC), a "hang up check in progress" message appears and the system pumps fresh air out of the tailpipe probe (i.e. reverse direction to sampling) to purge any HC accumulations in the sample line. Testing cannot proceed unless the sample dilution and auto zero conditions are complied with.
  3. The vehicle speed is set to 40 km/hr (+/- 1.6 km/hr). After the speed reaches the target range, the system allows 10 seconds for the vehicle to stabilize before collecting sample from the tailpipe. The readings for HC, CO, NOx, CO2 and O2 are monitored once per second during sample collection.

    In order for the test mode to terminate prior to the maximum mode time (Fast-Pass), the following conditions must be satisfied:

    1. the stable HC, CO and NOx readings must be less than a pre-determined percentage of the maximum allowable,
    2. the vehicle must have operated in the target speed range for at least 30 seconds.
  4. Conditions 3(i) and 3(ii) must be satisfied to "Fast Pass" a vehicle. The values printed on the inspection report for a "fast passed" vehicle are the average of the last 10 seconds of readings.
  5. A vehicle which never achieves stable readings or that has emissions above the allowable maximum will continue to operate on the loaded mode test until the maximum mode time of 90 seconds is reached. At this point, the 10 second average of the HC, CO and NOx readings will be printed on the inspection report. If the vehicle fails the test, a Diagnostic Trace Report is generated showing the HC, CO, NOx, CO2 and O2 readings for each of the 90 seconds of the test.
  6. Following termination of the driving portion of the test, the idle measurement is performed. The idle mode requires that the dynamometer speed be zero km/hr and that the engine rpm be less than 1150 rpm. The inspector is instructed to place the gear selector in PARK or NEUTRAL. Although vehicles with automatic transmissions tend to idle in DRIVE most of the time, the test procedure requires that idle emission samples be taken in PARK or NEUTRAL. (This has the minimal effect on emissions.) On 1988 and later technology vehicles, idle speed is often not adjustable.
  7. Once the computer has established the conditions described above, the system will wait 10 seconds in order to allow the vehicle's idle emissions to stabilize. When the system is ready, the sample is drawn from the tailpipe. The maximum mode time for the idle test is 30 seconds. A vehicle may "fast pass" at any time between 10 seconds and 30 seconds provided that the sample readings meet stability criteria and are less than the applicable maximum allowable.
  8. If the vehicle passed the driving portion of the test, the exhaust measurement process is stopped after the vehicle fast passes on the idle test or at the termination of the 30 second maximum mode time. The HC and CO readings printed on the inspection report are the 10 second average. NOx emissions are not monitored during the idle phase since it is unusual for vehicles to produce any significant quantity of NOx at idle.

Watch a video describing the ASM/Idle test procedure.