P157897 - P157897 CC Signal Abnormal (Euro Standard)

P157897 CC Signal Anomaly (Euro Standard) Technical Analysis

P157897 CC Signal Anomaly (Euro Standard) refers to the onboard charging management system detecting that physical signal parameters at the Control Circuit (CC, Control Circuit/Combination Current) pin exceed preset safety boundaries during direct current charging processes. This fault code belongs to the core definition of communication and connection detection faults, aiming to ensure that the charging interface can correctly identify handshake signals between the vehicle end and the AC grid when in a physical connection state, preventing electrical safety accidents or energy charging logic interruption caused by signal misjudgment.

Common Fault Symptoms

When the P157897 code is written into the control unit log, users and onboard systems typically experience the following perceptible phenomena:

• Charging Function Loss: The vehicle cannot enter direct current fast charging state, and the instrument panel charging indicator light shows no display or displays an error warning icon.
• Connection Recognition Failure: After inserting an external charging device, BMS (Battery Management System) or OBC (Onboard Charger) cannot confirm the charging pile readiness signal, causing the handshake process to interrupt.
• System Log Recording: The fault code persists, even if disconnected and reconnected without automatic reset, requiring clearing via diagnostic tools.

Core Fault Cause Analysis

According to Euro Standard definitions and electrical architecture logic, the triggering mechanism of this fault can be summarized into abnormalities in the following three dimensions:

• Hardware Component Failure: Mainly involves aging or physical damage of the external charging connection device (Charging Connector) itself, as well as failure of detection circuit components inside the onboard charger (OBC).
• Line and Connector Failure: Includes wire harness damage from vehicle end to OBC internal, poor contact at CC pins, short circuits or open circuits caused by aging insulation skin, and unstable signal transmission caused by oxidation and loose connector pins.
• Controller Logic Operation Failure: Involves control unit (Control Unit) internal algorithm misinterpretation of CC resistance value signals, leading to false reporting of threshold exceedance within normal ranges.

Technical Monitoring and Trigger Logic

The determination of this fault code relies on real-time dynamic monitoring by the onboard charger of physical layer connection signals. Specific trigger mechanisms are as follows:

• Monitoring Target: System monitors resistance value signals at CC (Combination Current/Control Circuit) pins in DC charging interfaces in real time.
• Numerical Judgment Logic: Control units continuously calculate the matching between currently detected $R_{\text{CC}}$ and specified thresholds. When satisfying the following inequality relationship, the fault is determined to be present: $$ R_{\text{CC}} \notin [\text{Threshold}{\text{min}}, \text{Threshold}{\max}] $$
• Trigger Operating Condition: Only when the vehicle is in DC Charging State (Vehicle DC Charging State) and during the system initial connection handshake period, if CC resistance value is detected to be outside specified thresholds, fault code P157897 is generated immediately and relevant data flows are recorded. This process aims to protect high-voltage loop safety, preventing unintended conduction on the high-voltage side caused by misjudgment of plug insertion.