1 - Select system test.
2 - Select "Request small lift".
If "Valve lift diagnosis not ready" appears, a fault may have been stored.
1. Erase the fault memory.
3 - Activate the system test with the key F8 immediately before acceleration with wide-open throttle.
The message "Drive link active" then appears.
NOTE: If "Request small lift" appears, the valves remain at small lift, i.e. the performance is reduced dramatically.
4 - Perform acceleration with wide-open throttle in 2nd gear, until "Valve lift diagnosis completed" (max. 4,000 rpm) appears.
At speeds above 4,000 rpm, misfires may be stored. Delete the fault memory and repeat the test.
NOTE:
- If a fault is detected, it is only recorded in the fault memory after 6,000 ignitions (at idling speed approx. 3 minutes waiting time).
- It is important to observe the oxygen sensors during acceleration with wide-open throttle or to record their behaviour with the data logger.
End
On Board Diagnostic
P0303
Misfiring, Cylinder 3
Function
To detect misfiring, the drop in engine speed which results when there is a partial lack of combustion at one or more cylinders is evaluated.
A distinction is made between emission relevant misfiring after start-up, emission relevant misfiring during the journey and misfiring which is
damaging to the TWC. (See fault text table).
The engine speed is measured with an inductive sensor that is located above the ring gear on the flywheel. The ring gear is divided into three
segments. For detection, the time between two segments is measured and the difference calculated. This difference is corrected by a mean value that
is developed over several segments, to compensate for engine speed fluctuations caused by driving conditions. If the corrected value is above a
specified threshold value which is dependent on engine speed and engine load, a misfire is detected. (See also Misfire detection description).
Diagnosis conditions
A cycle of 1,000 crankshaft revolutions is evaluated (for misfire damaging to the TWC, 200 crankshaft revolutions). The misfire rates are compared
with a threshold value. If the misfire rate is greater than the threshold value, a fault is recorded in the memory.
The Check Engine Malfunction Indicator Lamp (MIL) is switched on and stays on when the misfire rate lies above the threshold value at which the
emission limit values are exceeded during two consecutive driving cycles.
If the misfire rate may lead to permanent damage to the TWC, the Check Engine MIL flashes. If this misfire rate is subsequently no longer reached,
the MIL changes to a continuous light.