ACTRON Accumulated Misfire Counter (SI B12 31 18)

Publication date: 2018-12-01
Reference number: SI B12 31 18

ACTRON ACCUMULATED MISFIRE COUNTER

TECHNICAL SERVICE BULLETIN

Reference Number(s): SI B12 31 18, Date of Issue: December 01, 2018

BMW:	All vehicles equipped with OBDII systems
GROUP:	Engine Electrical Systems

SITUATION

In certain rare situations, intermittent drivability issues may not be severe enough to induce faults and require a very specific conditions to be observed.

CAUSE

Limitations if the diagnostic systems

CORRECTION

To aid in these situations, the accumulated misfire function is now available as an expanded capability for the Actron Scan tool. The Actron Scan tool (CP9670) was initially distributed through the automatic tool shipment program (SI B04 18 15 ) and is now available in the aftermarket. This supplemental diagnostic tool may be utilized in instances when no faults are stored and specific dynamic driving conditions are needed to reproduce the complaint. The Accumulated Misfire function will provide a live aggregate count of misfires detected in each cylinder. The misfire counter is incremented when the crankshaft speed fluctuates thus may occur when the engine speed changes. The misfire counts will reset to zero after the key is cycled and the engine is started.

NOTE: Misfire counts may be present in normal engine operation and do not necessarily indicate a fault. Further analysis and diagnostics will be needed to determine if the observed counts are caused by an underlying issue.

PROCEDURE

Update the Actron scan tool with the procedure outlined in "Actron Misfire Detection Update Procedure.pdf" .
Start the Accumulated Misfire function as described in the table below:
- Connect to the vehicle
- Complete the error code readout and emission system monitor readout
- Select Vehicle Diagnostics from the Main Menu
- Select Accumulated Misfire from the Diagnostic Menu
- Observe that some misfire counts may already be stored.
  NOTE: This does not indicate a fault and is caused by changes in crankshaft speed during normal engine operation.
- As the Misfire counts accrue, a bar graph will appear as a visual aid.
  NOTE: Depicted left, the most likely cause of the driveability complaint only affects cylinder three.
Test drive the vehicle in a manor to induce the complaint
Evaluate the results and continue diagnostics

WARRANTY INFORMATION

Further information about the Actron Scan tool can be found in SI B04 18 15

ATTACHMENTS

View PDF attachment Actron Misfire Detection Update Procedure