P0300

SYSTEM DESCRIPTION
The Powertrain Control Module (PCM) uses information from the Ignition Control (IC) module and the Camshaft Position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring the variations in the crankshaft rotation speed for each cylinder the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the three-way catalytic converter to overheat under certain conditions. The Malfunction Indicator Lamp (MIL) will flash ON and OFF when the conditions for three-way catalytic converter overheating are present.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0125, P0336, P0341, P0502, P0503, P1106, P1107, P1114, P1115, P1121, P1122, P1336, P1351, P1352, P1361, P1362, or P1374 are not set.
^ The engine speed is at least 525 RPM, and is no more than 5,900 RPM.
^ The system voltage is between 9-18 volts.
^ The ECT is at least -7°C (21°F), and is no more than 125°C (255°F).
^ The throttle angle is steady.

CONDITIONS FOR SETTING THE DTC
The PCM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed the mandated standard.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
^ The scan tool will indicate if a test has failed since the codes have been cleared. Misfire history will be stored and displayed for each of the cylinders at the time of the failure.
^ Incorrect rough road received from the EBCM or the EBTCM.
^ The Crankshaft Position (CKP) system variation learn procedure must be performed if any of the following conditions are true:
- The PCM has been replaced.
- DTC P1336 is set.
- The engine has been replaced.
- The crankshaft has been replaced.
- The crankshaft balancer has been replaced.
- The crankshaft position sensor has been replaced.
^ If the condition is intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-8:

Steps 9-15:

Steps 16-19:

The numbers below refer to the step numbers on the diagnostic table.
4. Depending on the cause of the misfire, the Misfire History Cyl # counter will display a large number for the misfiring cylinders. Values for the non-misfiring cylinders will be less than 1/2 as great as the misfiring cylinders. When investigating a misfire, always start with items associated with the cylinders that has the largest number of counts stored in the Misfire History Cyl # counter.
5. If the misfiring cylinders are companion cylinders, the condition is most likely linked to the ignition system.
9. Inspect for poor terminal connections, grooves, corrosion, pitting, and loose fit.
17. Inspect for the following conditions that may contribute to the engine misfire, including engine oil pressure, a damaged accessory drive belt or pulley, and damaged driven accessory, such as a generator, a water pump, or a drive belt tensioner. Inspect for loose or broken motor mounts.