How does a fault code arise in the Ignition System group?
The ignition group covers everything to do with igniting the mixture reliably and on time: spark plugs, coils, ignition driver circuits, the knock sensor and misfire counting.
There is no dedicated misfire sensor. The control unit watches the instantaneous crankshaft speed using pulses from the crankshaft position sensor; every combustion event accelerates the crank slightly, and in a cycle without combustion that expected acceleration does not happen, so the crank measurably stumbles. The module counts those stumbles. This has an important consequence: if the crank signal itself is faulty, the module can “see” misfires that are not there.
Whether the misfire is concentrated in one cylinder completely changes the diagnostic path. With a single-cylinder code a coil swap test is meaningful; with a random misfire there is no code to move, so you go straight to the common causes.
Fault codes in this group
The database holds 27 codes in this group. Each code has its own page with the meaning, possible causes and diagnostic steps:
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Data source: the CarCoding fault code database. Code definitions follow the SAE J2012 standard; manufacturers may use different wording for their own codes. Everything on this page is generated from the code-specific database records.