Diagnosis Information DME

P0303

Misfire, cylinder-selective

NOTE 1:
The fault types have special significance for misfires:
- Fault type "Implausible signal": exhaust-related fault after engine start-up
- Fault type "Below limit value": exhaust-related during the journey
- Fault type "Above limit value": fault damaging to catalytic converter

NOTE 2
- The totals error P0300 is always entered in addition to any other misfires. The misfires may have occurred in one or several cylinders.
- The misfire detection function can block the fuel injection for the remainder of the driving cycle after a permanent misfire is detected on the cylinder in question. Misfire detection remains active.

Diagnostic conditions
- Engine running
- Engine load > 4 to 25% depending on engine speed
- Intake air temperature > -30 °C (-22 °F)
- No fault in crankshaft sensor
- Testing for misfires while driving: smooth road surface conditions (= no bumpy track)

Possible fault causes
- If a misfire only occurs on one cylinder:
--> Electric fault in control line between DME and ignition coil
--> Spark plug connector faulty
--> Ignition coil faulty
--> Spark plug faulty
--> Secondary air
--> Mechanical or electrical fault in injection valve
--> Valve seat or valve faulty
--> Valve lift control faulty
--> Exhaust system blocked/narrowed
--> Foreign bodies in intake tract, this can lead to sporadic misfires on changing cylinders.

- When misfires occur on the banks:
--> Electric fault or loose contact in the control line to solenoid valve of camshaft adjustment
--> Solenoid valve of camshaft adjustment electrically/mechanically faulty or clogged
--> Hall sender rotor (sensor wheel) faulty/kinked
--> Secondary air
--> Intake camshaft adjustment too slow
--> Intake camshaft timing incorrect
--> Exhaust camshaft timing incorrect
--> Fault in the valve lift control
--> Oxygen sensor faulty (also: loose contact in wiring harness)
--> Exhaust system blocked/narrowed
--> Foreign bodies in intake tract, this can lead to sporadic misfires on changing cylinders.

- When misfires occur on both banks:
--> Incorrect/low-grade fuel
--> Tank empty
--> An engine-block heater is used
--> Secondary air
--> Exhaust system blocked/narrowed
--> Foreign bodies in intake tract, this can lead to sporadic misfires on changing cylinders.