P0300

P0300 00

Random Misfire Detected.







Fault symptom
Check Engine
(Check Engine lamp flashes if diagnostics has detected a misfire that is harmful to the catalytic converter).
Uneven running and misfiring.

On-board diagnosis

Type of diagnosis:
Continuous
Each misfire is registered and evaluated two different ways depending on the type of misfire.

Test 1
- Affects emissions.

Test 2
- Harmful to the catalytic converter.


Enable criteria:
General conditions for this DTC
- Positive engine torque (negative torque = engine breaking).
- Combustion signals from CDM are registered.

Test 1
- Number of combustions is registered.

Test 2
- The number of times no combustion signal is sent is tallied per cylinder every 200 engine revolutions. The total number of permissible misfires per 200 revolutions is indicated in a load and rpm-dependent matrix.

Fault criteria:
Test 1
- The number of times there was no combustion exceeds 3%.

Test 2
- The number of times no combustion signal was sent exceeds the number of permissible misfires. More than one cylinder has misfired.

Dependent:
P1312, P1315, P1341, P1342, P1343, P1344

System reaction to a fault:
None

OK report:
OK-report takes place at ignition OFF if no fault report is generated during the driving cycle.

Fault handling:
Test 1
- Type II
- (See Description of On-Board Diagnostics/Fault handling II, "Emission-related misfiring or fault in fuel system" for more information.)

Test 2
- Type I
- (See Description of On-Board Diagnostics/Fault handling I, "Catalyst damaging misfiring" for more information).

Checking the wiring harness
Move the wiring harness at several spots and in several directions to reveal intermittent breaks and short circuits. Check switches, connectors and crimp connections for oxidation, retracted pins and pin clamping force.

Diagnostic help
A cursory check is carried out on connectors and hoses. Then a through check is carried out on compression, ignition timing and fuel system.