Fault Conditions

P0300

Random Misfire Detected.










Fault symptoms
- CHECK ENGINE.
- Running unevenly and misfiring.

On-Board Diagnostics

Type of diagnosis:
- Continuous. But interrupted when fault criteria fulfilled and will not restart until next driving cycle.

Enable criteria:
- General conditions for this trouble code: Atmospheric pressure must exceed 72 kPa and the engine coolant and intake air temperature must exceed -7 degree C.
- Engine running. Main relay voltage exceeding 10 V. Ignition discharge module combustion signals registering. The number of missing combustion signals is accumulated for each cylinder every 1000 engine revolutions. The total number of accepted misfires during 1000 engine revolutions is specified in a load and engine speed-dependent matrix.

Fault criteria:
- Number of missing combustions exceeding number of accepted misfires.

Dependents:
- P1312 and P1334.

System reaction to a fault:
- Under high engine loads, closed loop will be blocked while misfiring occurs.

OK report:
- Provided fault criteria are not fulfilled during the driving cycle, the OK report will made when the ignition is turned off and before the engine stops.
Two other types of OK report can also be made:
Type 1: If a diagnostic trouble code has already been stored for the diagnosis and the same running conditions have occurred (coolant temperature above or below 71 degree C, engine speed ±375 rpm and load ±10%).
Type 2: If there is no diagnostic trouble code stored for the diagnosis or the same running conditions have not occurred.

Fault handling: (For more information, Fault Handling II, Emission-Related Misfiring or Fault In Fuel System)

- Type II.

Diagnostic help
If any other trouble codes have been generated, check whether fault diagnosis should be started on any of them first. Read Freeze Frame and change spark plugs.

Then make a general inspection of connectors and hoses and subsequently a thorough check of compression, ignition and fuel system.

Functions in the diagnostic tool related to the fault:
- Diagnostic status for the diagnosis.
- Misfire Cyl 1.
- Misfire Cyl 2.
- Misfire Cyl 3.
- Misfire Cyl 4.
- Multiplicative Adaptation, unit %
- Additive adaptation, unit mg/c.
- Closed loop, unit %.
- Purge Adaptation, unit %.
- Air mass deviation from calculated, unit %.
- Activating misfire counter reset.
- Activating ignition triggers.
- Activating injector test.
- Activating pump test.

For more information, refer to scan tool testing. Menu Read Values

Checking the wiring
Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short circuits. Observe the multimeter, diagnostic tool or test lamp during the check.

Proceed to Diagnostic Procedures Check Additional Diagnostic Trouble Codes In the Trionic System