This study investigates pulse-based diagnostic methods for identifying faulty cells within lithium-ion battery packs in electric and hybrid vehicles. Diagnostic measurements were conducted using a fully electric Volkswagen e-Golf under both dynamic driving (WLTP) and laboratory-based Hybrid Pulse Power Characterization (HPPC) test conditions. Voltage deviations among individual battery cells were analyzed to evaluate system reliability under constant load, peak load, and regenerative braking scenarios. Results revealed that peak load conditions provided the most informative insights for fault detection due to fewer but more significant voltage deviations. In contrast, constant load and regenerative braking conditions frequently exhibited minor deviations. These findings suggest that transient, high-current events are particularly valuable for early identification of cell degradation and faults. Future studies should further investigate the long-term relationships between detected deviations and overall battery health to enhance predictive diagnostics and optimize battery management strategies.