Transcript Document

Triggers for OBDII I/M Programs
Rob Klausmeier
dKC
1
What Are Triggers?
• Triggers are reports to identify stations
performing fraudulent or inaccurate
inspections.
• Triggers can be grouped into the following
categories:
– High Probability Clean-Scanning Triggers,
– Triggers to Identify Facilities with out-ofrange inspection results
2
High Probability Clean-Scanning
Triggers
• Mismatch between expected and actual
OBDII parameters.
• Questionable Retests – Short time
between failing and passing tests
• Questionable Retests – Mismatch
between initial test OBDII parameters
and retest OBDII Parameters
3
OBD Parameter Mismatch
• Report can identify mismatches between OBDII
parameters for vehicle entered into inspection
record and parameters downloaded from OBDII
system
• % of vehicles with different OBDII parameters:
– Monitors supported – 100%
– Communication protocol – 100%
– PID Count – 100%
– PCM ID – 100%
– PCM VIN – 16.8%
– Calibration ID (CAL ID) – 34.9%
– Calibration Verification number (CVN) – 34.6%
4
% of Vehicles Reporting
CAL ID, CVN and PCM VIN
Model Year
CAL ID
CVN
PCM VIN
1996-1999
0.00%
0.00%
0.00%
2000
46.25%
43.00%
13.13%
2001
77.52%
79.65%
42.58%
2002
91.39%
90.38%
47.43%
ALL
34.93%
34.59%
16.82%
5
OBD Parameter Mismatches
• Currently, the only parameter that can positively
identify clean scanning on initial tests is PCM
VIN.
• A look-up table should be developed to identify
the following for specific years, makes and
models.
–
–
–
–
–
–
Monitors supported,
Communication protocol,
PID Counts,
PCM IDs,
CAL IDs,
CVNs
6
PCM VIN Mismatches
• Identify mismatches between entered VIN and PCM
VIN. Inspectors may be attempting to pass vehicles with
OBDII faults by scanning problem free vehicles instead
of vehicles that should be inspected.
– If the vehicle has an electronic VIN available through
the vehicle’s OBDII system, clean scanning cases can
be identified by comparing entered VIN with VIN
provided by vehicle’s OBDII system.
– PCM VINs need to be manipulated to accurately
identify mismatches.
• For example, dKC recommends comparing last 5 VIN digits.
7
High Probability Clean-Scanning
Triggers – Questionable Retests
• Trigger reports can identify questionable
“fail previous test” / “pass next test” pairs.
– Short-Time between failing and passing tests
– OBD Parameter mismatches on retest passes
8
Short Time Between
Failing and Passing Inspections
• It is difficult to repair OBD failures and get
failing vehicles to pass in a short time
period:
– MIL-On Fails – It takes time for the MIL to go off or
readiness monitors to reset if codes are cleared
– Readiness Fails – It takes time for readiness
monitors to set to ready.
• Stations that often show short time periods
between initial test failures and retest passes
could be performing fraudulent inspections.
9
10
Questionable Retests
Mismatch in OBDII Parameters
• Mismatch between initial test OBDII
parameters and retest OBDII Parameters:
–
–
–
–
–
–
Supported readiness monitors
COM Protocol
PID/PCM identifiers
CAL ID
CVN
PCM VIN
• Mismatches between initial tests and retests
could indicate that the inspector clean-scanned
vehicles on retests.
11
Readiness Monitor Mismatch
12
Triggers To Identify Facilities With OutOf-Range Inspection Results
• Too low or too high normalized
failure rates
• Too low or too high KOEO failure
rates
• Too low or too high DLC failure
rates
13
Too Low or Too High
Normalized Failure Rates
Too low or too high failure rates indicate
possible fraudulent activities or equipment
problems. Normalized fail rates can be
calculated as follows:
• Compute overall initial test OBDII failure rate (all
facilities) by model year.
• Tabulate percentage breakdown of initial OBDII
tests by facility by model year.
• Weight the overall failure rate by model year by the
percentage breakdown for each facility by model
year.
• Compute the differences by facility between the
actual failure rate and the normalized failure rate.
• Adjust differences by standard deviation.
14
Normalized Fail Rates
Normalized vs Actual Fail Rates -- OBDII Inspections
25.00%
20.00%
Actual
Normalized
15.00%
10.00%
5.00%
0.00%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
15
Out-Of-Range Inspection Results
High KOEO or DLC Fail Rates
• Stations/Inspectors with a high
percentage of failures due only to MIL
not on during KOEO.
• Stations/Inspectors with a high
percentage of DLC not found or
damaged.
16
Triggers Summaries
• Triggers should be tabulated by station.
• Stations with more than one minor trigger
or any major trigger, e.g. Large emission
reductions in a short time period, should
be visited more frequently.
• Many stations have >1 Trigger. About ¾ of
the trigger incidences are in stations that
had >1 Trigger.
17
Conclusions
• Trigger reports are being generated
frequently to identify stations performing
improper inspections.
18