#ignition
10 posts in Car Diagnostics blog about "ignition" — OBD-II diagnostics, DTC codes, repair. ← All posts
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Engine keeps running after you switch off: what causes run-on
An engine that shudders on for a few seconds after the key is out was a common fault decades ago. On a modern car it means something quite different.
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Engine cranks but will not fire: spark, fuel or timing
A healthy-sounding crank with no start narrows the problem to three systems. Knowing which one to test first, and what OBD can tell you before you open anything, saves the whole afternoon.
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Key stuck in the ignition: causes and safe fixes
On an automatic this is usually the gear selector, not the lock. On a manual it is usually the steering lock. Both are free to fix if you try them before forcing anything.
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P0316: misfire detected on startup — the cold-start-only fault
P0316 only counts misfires in the first seconds after cranking. That narrow window points at a specific short list of causes that a warm-engine test will never reproduce.
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Steering wheel locked and the key will not turn
Nine times out of ten this is not a fault at all, and the fix takes five seconds. The other one time is a lock cylinder, and it is worth knowing which you have before calling anyone.
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Spark plugs: when to change them and why "still working" is not an argument
A plug does not fail abruptly — it degrades, and the coil degrades with it. Types, intervals, and why a dearer plug is not always better.
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Ignition coils: the symptoms people mistake for spark plugs
Coils and plugs produce similar symptoms but are tested differently. How swapping separates them, and why coils die in groups.
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P0335: the crankshaft position sensor — the one the engine cannot start without
The car cranks and never catches. No spark, no fuel, and possibly no codes stored. The sensor without whose signal the control module will not even begin to try.
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P0340: camshaft position sensor — why the car only starts on the second try
The engine will not start first time, occasionally stalls and restarts immediately. That is the camshaft sensor signature: it does not stop the engine permanently, it makes it unpredictable.
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Spark Plugs and Ignition Coils: OBD-II Diagnostics — P030X Misfires
How to diagnose faulty spark plugs and ignition coils with OBD-II: P0300–P0308 codes, Live Data Misfire Count, cylinder elimination method — no oscilloscope needed.