Tracker 4WD L4-2.0L VIN C (1999)
to the TWC catalyst.
Extinguishing the MIL
The PCM will turn off the MIL after three consecutive trips that a test passed has been reported for the diagnostic test that originally caused the MIL to
illuminate.
The DTC will remain in the PCM memory and the Freeze Frame record until forty (40) warm-up cycles have been completed and no faults exist.
An MIL that was illuminated by either a fuel-trim DTC or a misfire-related DTC has additional requirements that must be met in order to turn OFF the
MIL. The additional requirements are as follows:
^
The diagnostic tests that are passed must occur within 375 RPM of the RPM data stored at the time the last test failed.
^
The diagnostic tests that are passed must occur within ten percent of the engine load that was stored at the time the last test failed.
^
The diagnostic tests that are passed must occur at engine temperature conditions (warmed up or warming up) that are similar to those stored at the
time the last test failed.
Meeting these requirements ensures that the fault which turned on the MIL has been corrected.
DTC Types
DTCs are categorized by type. The type indicates the action the PCM will take in recording the DTC failure and illuminating the MIL. The following
table indicates what action the PCM takes for the 3 different DTC types when a DTC failure occurs.
In order for a type B DTC to request MIL illumination the DTC must fail in two consecutive drive trips in which the DTC tests.
Refer to Diagnostic Trouble Code (DTC) List for the type of DTC the particular PCM supports.
There are two type C DTCs. The C1 type DTC will illuminate an information lamp or display a message. The CO type DTC DOES NOT illuminate an
information lamp or display a message. Type CO DTCs were formerly referred to as Type D.
Always refer to the diagnostic support information within each DTC to obtain the Action Taken when the DTC sets and the Conditions for Clearing the
DTC. These will indicate any variations from the general type A, B and C actions.
Special Cases of Type B Diagnostic Tests
The PCM has the capability of alerting the vehicle operator to potentially damaging levels of misfire. A misfire condition that may potentially damage
the catalytic converter as a result of high misfire levels will command the PCM to flash the MIL at a rate of once per second. This once per second
flashing of the MIL will occur during the entire time that the catalyst damaging misfire condition is present. This flashing of the MIL is unique to the
misfire diagnostic.
Maintenance Schedule
Refer to the General Motors Maintenance Schedule of the appropriate service category for the maintenance that the owner or the technician should
perform in order to retain emission control performance.
Serial Data Communications
Regulations require that all automobile manufacturers establish a common communications system. The communication between the powertrain control
module and the off-board diagnostic equipment (scan tool) is achieved on a serial communication line. Serial data is sent in linear form, one bit at a time,
over the communication line.
ISO Keyword Protocol 2000
This vehicle utilizes the International Organization for Standardization (ISO) communications protocol Keyword (KW) 2000 message structure. The
KW-2000 protocol allows for the interchange of digital information between the on-board emission-related engine control modules of road vehicles and
the OBD 2 scan tool as specified in SAE J1978. This communication enables the vehicle to be in compliance with the California Code of Regulation.
The KW-2000 protocol is already in use by many automotive manufacturers worldwide.
