Emission inspection and maintenance (I/M) programs
Some states have vehicle
emission inspection programs
which include OBD
(On Board Diagnostics)
checks. The OBD system
monitors the operation of
the emission control system.
If the malfunction indicator
lamp comes on
The OBD system determines
that a problem exists somewhere
in the emission control
sy ...
Diagnosis system
Description
When troubleshooting obd ii (on-board diagnostics)
vehicles, the intelligent tester (complying with sae
j1987) must be connected to the dlc3 (data link
connector 3) of the vehicle. Various data in the vehicle's
ecm (engine control module) can be then read.
Obd ii regulations ...
Air-fuel ratio (a/f) and heated oxygen (ho2) sensor
monitors (active air-fuel ratio control type)
Preconditions
The monitor will not run unless:
2 Minutes or more have elapsed since the engine
was started.
The engine coolant temperature (ect) is 75°c
(167°f) or more.
Cumulative driving time at a vehicle speed of 48
km/h (30 mph) or more exceeds 6 minutes.
Air-fuel rat ...