DIAGNOSING THROTTLE POSITION SENSOR SIGNAL INTERFERENCE IN ELECTRONIC CONTROL UNITS: EXPERIMENTAL EVIDENCE AND IMPLICATIONS FOR AUTOMOTIVE VOCATIONAL EDUCATION

Abstract

Accurate sensor signals are essential for reliable Electronic Control Unit (ECU) operation in modern automotive systems; however, Throttle Position Sensor (TPS) degradation may generate intermittent signals that are difficult to detect through visual inspection alone. This study aimed to identify the mechanism of TPS interference, examine its effects on ECU signal processing and engine performance, and evaluate corrective measures with implications for automotive vocational diagnostics. An experimental diagnostic approach was conducted on a Daihatsu Xenia 1.0 Non-VVT-i equipped with an EJ-DE engine. Data were obtained through physical inspection, TPS output-voltage measurements across different throttle-opening angles, OBD-II Diagnostic Trouble Code (DTC) analysis, ECU live-data observation, and post-repair verification. The results revealed wear on the TPS resistive track and mild connector corrosion, producing unstable voltage fluctuations of 0.3–4.8 V within the 45°–55° throttle-opening range. The anomalies were associated with DTCs P0121, P0122, P0300, and P0171, unstable idle speeds of 550–950 rpm, acceleration hesitation, and ECU fail-safe operation. Replacing the TPS, cleaning the connector, recalibrating the system, and clearing the DTCs restored linear voltage output, stabilized idle speed at approximately 750 rpm, and normalized acceleration response. The study concludes that TPS interference disrupts ECU functional accuracy without causing permanent internal ECU damage. These findings provide an evidence-based diagnostic sequence that can strengthen troubleshooting competencies in automotive vocational education. Future research should validate the diagnostic framework across different vehicle models, sensor technologies, and vocational learning environments.