General Information

Engine Control

P2502 Battery Voltage Rationality - General Information

Component Location





General Description

Many control units have applied to vehicle as it becomes more electronical. These units control their own system based on information from diverse sensors. Therefore necessity of common use of diverse sensor information and importance of stable power supply are gathering strength. Battery sensor is mounted on battery (-) terminal. It transmits battery voltage, current, temperature information to ECM. ECM controls generating voltage by duty cycle based on these signals.

DTC Description

ECM sets this code when there is difference between battery voltage at power supply terminal of ECM and ECM commend voltage.

DTC Detecting Condition





Diagnostic Circuit Diagram





Signal Waveform & Data
















Fig.1) Normal waveforms of COM, FR terminal of alternator at idle.
Fig.2) Normal waveforms of COM, FR terminal of alternator under high electronic load condition
Fig.3) Normal waveforms of COM, FR terminal of alternator at ig on under connector disconnected condition.
Fig.4) Normal waveforms of COM, FR terminal of alternator at idle under connector disconnected condition.