MULTI-METHOD DIAGNOSIS OF CRANKSHAFT POSITION SENSOR INTERFERENCE IN A THREE-CYLINDER ENGINE FOR AUTOMOTIVE VOCATIONAL TRAINING

Abstract

Crankshaft Position (CKP) sensor interference can disrupt crankshaft synchronization and contribute to asymmetric ignition failure in Electronic Control Unit (ECU)-based engine management systems. This study analyzed CKP parameter deviations in a single Daihatsu Xenia 1.0 non-VVT-i vehicle equipped with an EJ-DE three-cylinder engine and examined a low-cost, multi-method diagnostic sequence for workshop and automotive vocational-training contexts. The study was designed as a single-vehicle diagnostic experimental case comparing operational reference specifications, the faulty condition, and the post-repair condition. Data were obtained through OBD-II scanning, cold and hot coil-resistance measurements, reported signal-amplitude and frequency measurements, and CKP air-gap inspection. In the faulty condition, DTCs P0335 and P0336 were recorded, idle speed fluctuated at 650-710 rpm, STFT reached +18-22%, coil resistance increased to 3,180 Ω at 20°C and 3,740 Ω at 80°C, the reported signal amplitude decreased to 0.3-0.5 Vpp, frequency fell to 410 Hz, and the air gap was recorded at 0.58 mm. After sensor replacement and air-gap adjustment to 0.30 mm, the measured parameters returned to the operational reference ranges. These findings corroborate a diagnosis involving concurrent electrical and mechanical abnormalities in this specific vehicle, but the combined repair does not isolate the independent effect of each abnormality. The diagnostic sequence may support evidence-based troubleshooting practice in automotive vocational education; its instructional effectiveness and transferability require further validation.