#no start
9 posts in Car Diagnostics blog about "no start" — OBD-II diagnostics, DTC codes, repair. ← All posts
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Starts then dies within seconds: immobiliser, fuel or idle control
An engine that fires and stops within two seconds is telling you something specific, and the timing narrows the cause more than any code.
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Hard to start when hot: the fault that hides on a cold morning
A car that starts perfectly cold and struggles when hot has a specific set of causes, and heat is doing the diagnosis for you.
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P0616 and P0617: starter relay circuit low and high
A click and no crank sends most people to the starter motor. These codes point at the circuit that commands it, which is usually cheaper and easier to reach.
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Push-button start does nothing: brake switch, fob or module
Nothing at all when you press the button is a different fault from cranking and not starting. The list of causes is short and mostly cheap.
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U0109: lost communication with the fuel pump control module
The module that varies pump speed has stopped answering. The car may not start, and the cause is often a connector under the rear of the vehicle.
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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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Will not start in the cold: five causes in the order you should check them
Frost does not create new faults — it finishes off the ones already marginal. Diagnosis by symptom: does not crank, cranks without catching, catches then stalls. Each leads somewhere different.
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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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Car won't start: how OBD-II tells an immobilizer fault from fuel/electrical
Step-by-step algorithm for "no-start": how OBD-II tells in 5 minutes whether the issue is the immobilizer (P1602, B10CC), fuel pump, starter, battery or ECU.