DTC Advanced Diagnostics: P0300, P0301, P0302, P0303, P0304
DTC P0300:Random Misfire Detected
DTC P0301:No. 1 Cylinder Misfire Detected
DTC P0302:No. 2 Cylinder Misfire Detected
DTC P0303:No. 3 Cylinder Misfire Detected
DTC P0304:No. 4 Cylinder Misfire Detected

General Description
The basic operating principle of the engine misfire detection monitor is based on the calculated angular acceleration of the engine crankshaft during each individual combustion event. In case of a lack of combustion, or insufficient combustion in any cylinder, the CKP pulse plate which is attached to the crankshaft requires a longer time to pass the crankshaft position (CKP) sensor. The associated acceleration value will overshoot a calibrated threshold (indicating a large deceleration) which will then lead to a misfire event being detected by the system. There are two types of misfire detection:
Catalyst damaging misfire
Misfire events are counted within intervals of 200 crankshaft revolutions. Dependant on the current engine speed and load, a weighted fault counter will increment with each new misfire event. Catalyst damaging misfire events are evaluated bank specifically. A fault entry will occur anytime the weighted misfire counters exceed a calibrated threshold for a given engine bank. With this condition, the powertrain control module (PCM) stores a DTC. A cylinder specific DTC will be recorded for each cylinder that contributes at least 25 % of the total misfire.
Emission relevant misfire
Misfire events are counted during 1,000 crankshaft revolution intervals after engine start. At the end of each 1,000 crankshaft revolution period, the total number of detected misfire events is compared to a fault threshold. If the number of detected events exceeds a threshold, a fault counter will be incremented. After exceeding the emissions relevant fault threshold for the fourth occurrence, the PCM stores a DTC. A cylinder specific DTC will be recorded for each cylinder that contributes at least 10 % of the total misfire.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Continuous
Sequence
None
Duration
–
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Engine coolant temperature [ECT Sensor 1]
-30 °F (-22 °C)
–
Engine speed [Engine Speed]
450 rpm
7,000 rpm
Engine torque
3.13 to 12.89 %
–
Fuel feedback
Other than during fuel cut-off operation
Other
ABS/VSA not active
Test-drive on a flat road to avoid misdetection
[ ]: HDS Parameter

Malfunction Threshold
Catalyst damaging misfire
Misfire rate is more than 5 - 19.84 %*. (A cylinder specific DTC will be recorded for each cylinder that contributes at least 25 % of the total misfire.)
*: Depending on engine speed and load
Emission relevant misfire
If the misfire occurs 100 times during 1,000 crankshaft revolutions, a fault counter is incremented. The condition occurs 4 events. (A cylinder specific DTC will be recorded for each cylinder that contributes at least 10 % of the total misfire.)

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
Ignition system failure
Fuel supply system failure
Intake air system failure

Confirmation Procedure
Operating Condition
1.
Start the engine. Hold the engine speed [Engine Speed] at 3,000 rpm without load (in neutral) until the radiator fan comes on.
2.
Drive the vehicle at constant vehicle speed for at least 2 minutes.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details
Conditions for setting the DTC
Catalyst damaging misfire:
If a catalyst damaging misfire occurs, the MIL will blink in each interval that catalyst damaging misfire is detected. The MIL will cease from blinking after an interval passes where no catalyst damaging misfire is detected. After this point, the MIL will either be extinguished or will remain illuminated. This behavior depends on whether catalyst damaging misfire has been detected in one drive cycle (one occurrence) or in two drive cycles (two occurrences).

Emission relevant misfire:
If an emission relevant misfire occurs during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.
Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive drive cycles in which the engine conditions are similar to the first time the malfunction was detected. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.