Misfire Counters

Throttle Position Sensor Connector:

The Misfire Counters graphic illustrates how the misfire diagnosis and the diagnostic executive use the misfire counters (accumulators). When a misfire diagnostic test fails and reports to the diagnostic executive that a misfire condition exist, the diagnostic executive reviews all of the misfire counters in order to store the most current misfire information.

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.