P0300

Wiring Diagram:

Engine Misfire Detected:

P0300- ENGINE MISFIRE DETECTED
The crankshaft position (CKP) sensor sends 58 pulses per crankshaft revolution to determine the position and RPM of the engine at various degrees of rotation. The crankshaft reluctor wheel contains 20 notches for every 1200 of crankshaft rotation except for two missing notches used to detect cylinder #1 TDC. The ECM bases misfire diagnostics on the principal that at a given speed and load, the time to pass 20 notches on the crankshaft between firing events should be below a certain threshold. If the time to pass 20 notches exceeds a calibrated time, a misfire is detected on the previous cylinder. Under certain conditions, the ECM will monitor misfires in both 200 (catalyst damaging counter) and 1000 (emission related counter) crankshaft revolution tests. If a certain number of misfires (greater than 30 out of a 1000 revolution test, or greater than 45 out of four consecutive 1000 revolution tests) occur over a certain number of engine revolutions, DTC P0300 will set. The MIL will then be commanded On after two consecutive drive cycles if DTC P0300 fails again. The MIL will turn Off after three consecutive passed drive cycles meeting the same criteria or 80 passed drive cycles if the criteria could not be met. DTC P0300 sets if specific or random cylinder misfires have occurred for a certain length of time.

DTC PARAMETERS
DTC P0300 will set if specific or random cylinder misfires have been detected after a 1000 revolution test(s) when:
^ Sum of the misfire counts are greater than 30 in a 1000 engine revolution test or greater than 45 in four consecutive, 1000 engine revolution tests
^ Engine speed is between 520 and 6520 rpm
^ Engine run time is greater than 5 seconds (2000 and 2001 only)
^ Traction control is not active
^ IAT is greater than -8°C (17°F)
^ EVAP diagnostics are not running
^ No CKP or TP sensor DTCs have been set

NOTE: The ECM must complete the entire 1000 revolutions before DTC P0300 will set. DTC P0300 diagnostic runs continuously once the above conditions have been met.

P0300 is a type B DTC

DIAGNOSTIC AIDS

IMPORTANT: If an EGR, EVAP purge solenoid, fuel injector, HO2S sensor 1 or MAF sensor DTC is also set. diagnose that DTC first.

IMPORTANT: The ECM will set DTC P0300 even if a specific cylinder is misfiring. If a specific cylinder misfire is also set, diagnose that DTC first.

IMPORTANT: If a specific cylinder misfire occurs for longer than 15 seconds, the ECM will command that cylinder fuel injector Off for the rest of the ignition cycle even if the fault is corrected.

IMPORTANT: The ECM automatically and continuously learns the crankshaft variation between notches under all engine speeds and loads. No manual procedure is required.

Use Scan tool to monitor MISFIRE CURRENT CYL. 1-6 while simulating different engine load conditions in the stall. The Scan tool active misfire counter should pick up intermittent misfire conditions.
^ Fuel pressure: 269-338 kPa (39-49 psi)
^ EGR SENSOR closed position value range: 0.5-1.0 volts
^ Spark plug gap: 0.045 in., not adjustable

NOTE: The misfire history counters will only be erased when DTCs are cleared using Scan tool.