Tracker 4WD L4-2.0L VIN C (1999)
Catalyst Monitor (Good Catalyst)
A good TWC catalyst will show a very active output voltage on the pre-catalyst heated oxygen sensor (1). A good catalyst, 95 percent hydrocarbon
conversion, will show a relatively flat output voltage on the post-catalyst heated oxygen sensor (2).
Bad Catalyst
Catalyst Monitor (Bad Catalyst)
A degraded, or bad, TWC catalyst, 65 percent hydrocarbon conversion, will show greatly increased activity in the output voltage from the post-catalyst
heated oxygen sensor (2). The degraded catalyst post-catalyst HO2S output voltage will therefore appear similar to the typically active output voltage of
the pre-catalyst heated oxygen sensor (1).
Misfire Monitor Diagnostic Operation
The misfire monitor diagnostic is based on crankshaft rotational velocity (reference period) variations. The PCM determines the crankshaft rotational
velocity using the crankshaft position sensor and the camshaft position sensor. When a cylinder misfires the crankshaft actually slows down momentarily.
By monitoring the crankshaft and the camshaft position sensor signals, the control module can calculate when a misfire occurs.
For a non-catalyst damaging misfire, the diagnostic will be required to report a misfire that is present within 1,000 to 3,200 engine revolutions.
For a catalyst damaging misfire, the diagnostic will respond to a misfire that is within 200 engine revolutions.
Rough roads may cause a false misfire detection. A rough road will cause torque to be applied to the drive wheels and the drive train. This torque can
intermittently decrease the crankshaft rotational velocity and cause a false misfire detection.
