5-Volt Pulse on value. If the voltages between spikes (on Pulses) has decreased by .157 volts. The O2 Heater
monitor passes and all testing is stopped this trip. Secondly, the voltage difference between the Pulse on voltage
is compared to next Pulse on voltage and is less than the prior voltage Pulse on, for 10 out of the 30 Pulses
(33%), this indicates a Heating Trend and the O2 Heater Passes. If neither a Heating Trend nor the Absolute
voltage is reached, the O2 Heater monitor fails 1 trip and the Freeze Frame Data is stored.
Misfire Monitor
Misfire monitor is continuously running during engine operation. For the Misfire monitor to be enabled, the
Adaptive Numerator must be learned since battery disconnect and every Key on there after (known as Power-on
learning). The Adaptive Numerator is a software learning routine that tells the PCM where the crankshaft slots
are. Since every crankshaft is different, the PCM must learn exactly where its particular crankshaft slots are;
otherwise its RPM calculations would be wrong. After a battery disconnect and then a power-up of the PCM,
the Adaptive Numerator is set to a value which it would be at if everything were perfect (crankshaft slots,
sensors, PCM hardware, etc.). If the Adaptive Numerator is equal to the default value, no learning has happened
and the Misfire Monitor will not run. To allow the PCM to learn the Adaptive Numerator, the following must
happen:
z
Open Throttle.
z
Engine Cool Temp Above 100°F; Or if below 100°F, Wait For ECT Rise Of 59°F.
z
More Than 10" Vacuum.
z
Above 1200 RPM.
z
Below 3000 RPM - A/T.
z
Below 3488 RPM - M/T.
Once the PCM has learned the Adaptive Numerator, the Misfire Monitor will run.
Fuel System Monitor
Fuel System monitor is continuously running during engine operation.
1995-2002 JTEC
OBD-II Monitor Enabling Criteria RWD/4WD JTEC PCM Equipped Vehicles
The following procedure has been established to assist technicians in the field with enabling and running OBD-
II Monitors on RWD/4WD trucks and Jeep models equipped with Jeep/Truck Engine Controller (JTEC). The
order listed in the following procedure is intended to allow the technician to effectively complete each monitor
and to set the CARB Readiness Status in the least time possible.
NOTE:
Once the monitor run process has begun, do not turn off the ignition. By
turning the ignition key off the monitor enabling conditions will be lost. Only the
O2 Heater Monitor runs after key off.
NOTE:
By performing a battery disconnect, or erasing diagnostic trouble codes, the
1998 Chevrolet Pickup C1500
DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors