This bulletin applies to Audi A8 vehicles, where DTC P0300 (random/multiple cylinder misfire) or P0301 – P0312 (cyl 1 – cyl 12 misfire) is detected. The engine may have reduced performance without significant loss of power or stalling.
Misfire faults causing MIL illumination can occur for a number of different reasons not directly related to ignition coil operation. Proper GFF misfire diagnosis must be followed before replacing any ignition coils. In order to repair the vehicle correctly, try to obtain as much information as possible from the customer about the symptoms of the condition and when it occurred.
- In what situation (turning, etc.) does the condition occur?
- Under what environmental conditions (road conditions, weather, temperature. Start conditions, etc.) does the condition occur?
- What is the operating situation of the vehicle (activated electrical equipment, gear selection, etc.) when the condition occurs?
- Can the complaint be reproduced?
1. Read out the data memory of all engine control units, and note the environmental conditions on the DTC log. If there are other entries in addition to combustion misfires, address these other entries before addressing the cylinder misfires. If DTC P0301 – P0312 is accompanied by P1250 (fuel level too low), it is likely the faults occurred due to low fuel level and not a coil malfunction.
2. Try to duplicate the complaint based on the environmental conditions at the time the DTC was set. The freeze frame data gives important indicators for the traceability of the complaint.
3. Review the vehicle repair history for previous misfires or maintenance service that could be related to the current complaint.
4. Observe the requirements of GFF (guided fault finding) Perform GFF in full according to the test plan sequence. Do not skip any steps.
5. In the case of single cylinder misfires, before replacing components, determine whether the complaint migrates to the other cylinders after exchanging the coils. If the misfire migrates to the cylinder the coil moves to, replace the affected coil.