C 3500 Truck 2WD V8-454 7.4L VIN J SFI (1999)
In the example illustrated by the Misfire Counters graphic, a misfire DTC has been set and the misfires are stored in more than one History Misfire
counter (accumulator). The cylinder number 1 History Misfire and Current Misfire counters indicates a far greater number of misfires than the other
cylinders. The misfires stored in the cylinder number 2 and the cylinder number 4 History Misfire counters (accumulators) indicate the erratic rotation of
the crankshaft caused by the misfire of number 1 cylinder.
In this example, viewing the Current Misfire and History Misfire counters indicate that a true misfire is present and the malfunction is located at cylinder
number 1.
Use a scan tool in order to monitor the misfire counters data. Identify which cylinder or cylinders are misfiring. Inspect the systems and components
common to the cylinders if multiple cylinders indicate a misfire is present.
Fuel Trim System Monitor Diagnostic Tests
The fuel trim monitor diagnostic tests monitor the fuel trim values. When the diagnostic tests indicate that the fuel trim system has reached the limits of
fuel control at certain engine operating conditions, a fuel trim DTC will set.
Component Diagnostics
The component diagnostics are tests that monitor and evaluate the emission related input components and output components related to the control
module. The control module tests the components, the components circuits, and the performance of these components.
