Compression vs leak-down: COMPRESSION TEST: measures cylinder pressure during cranking. Tells you: are all cylinders healthy? Relative differences. Cheap and quick — can DIY. Limitations: does not tell you WHERE compression is lost. LEAK-DOWN TEST: introduces pressurized air into cylinder at TDC. Measures percentage of air that leaks out AND tells you WHERE: air from oil filler = rings and cylinder walls. Air from exhaust = exhaust valve leaking. Air from intake = intake valve leaking. Air from radiator = head gasket. Air from adjacent cylinder = head gasket between cylinders. Leak-down = more information. Compression = initial screening. Use both for complete picture.
Compression test vs leak-down test — which gives more information?
Mechanic wants to do leak-down test. What is the difference from compression test? This fault code is stored when the engine control unit detects a specific fault condition. Common causes include sensor failures, wiring faults, and component wear. Always read additional fault codes before replacing parts — multiple codes together provide a clearer diagnosis. Clear the code after repair and test drive to confirm the fault does not return.
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⚙️ Possible Causes
Onarım / Çözüm
Based on 76 driver confirmations
⚠️ Yanlış Teşhis mi?
No commonly reported misdiagnoses for this fault yet. If you have replaced a part that did not fix this problem, submit a wrong diagnosis report — it helps other drivers avoid the same costly mistake.
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