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Car: 2005 CHRYSLER 300C 5.7 HEMI (83W)
Join Date: May 2007
Location: Stafford UK
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Fault Code: P0300
EOBD / ISO Description
Random / Multiple Cylinder Misfire Detected
Component / System Description
A common method of detecting misfires is to monitor the signal from engine speed sensor to check crankshaft acceleration / speed during each power stroke; this provides an indication of the power / torque contribution provided by the cylinder (compared to the other cylinders). Any fault with the cylinder, including mechanical faults, fuelling, ignition (petrol engines) or other faults affecting combustion, will affect the power / torque produced by the cylinder. Misfires can also be detected by the oxygen / lambda sensor, due to high oxygen content (unburned oxygen) in the exhaust gas. Also note that there is reference to manufacturers monitoring the strength of exhaust pressure pulses (which will be weak if a misfire exists); a weak pressure pulse is then linked to an individual cylinder by using cylinder identification sensors (cam shaft sensor etc).
Meaningful description and quick check
The fault code is indicating that there is a random misfire but it is not identifiable to specific cylinders. It is likely that the fault is causing erratic fluctuations of the crankshaft speed (or exhaust pressure pulses) which are not consistent to any one cylinder or group of cylinders. The fault could be related to any aspect of the engine operation including: fuelling, ignition (petrol engines), air leaks, mechanical condition etc. Also check (as applicable) for faults with variable valve timing, EGR and other emission control systems. It is also possible that there could be an engine position / speed sensor related fault.
NOTE 1. Check for other fault codes that could provide additional information. NOTE 2. If a fault cannot be located with the applicable components or wiring, it may be necessary to check operation of the control unit (ECU). NOTE 3. Communication between control units / modules can pass through a CAN-Bus system; check for CAN-Bus related faults and fault codes.
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