P159600 - P159600 CP Duty Cycle Fault

Fault Definition

P159600 CP Duty Cycle Fault refers to an abnormal determination of communication parameters for the Control Pilot (CP) signal when the On-Board Charger (OBC) or Power Supply Unit identifies AC Charging Status. In the handshake protocol between electric vehicles and AC charging piles, the CP signal is typically used to transmit voltage and current limit information, with its core carrier being a duty cycle signal in Pulse Width Modulation (PWM) form. This DTC indicates that during real-time monitoring, the vehicle's internal control unit failed to detect a CP Duty Cycle Signal conforming to preset communication specifications.

From a system architecture perspective, this DTC marks an interruption or distortion in the "communication feedback loop" within the charging control logic. When the on-board power supply unit exchanges parameters with external energy supply equipment (EVSE), if the level width ratio returned by the CP pin exceeds the safety window set internally by the controller, the system judges the communication handshake as failed. This definition excludes pure mechanical locking issues, focusing instead on the abnormal response of the Electronic Control Unit (ECU) to analog/digital signal processing logic, belonging to the high-level fault diagnosis category of charging system electrical communication.

Common Fault Symptoms

Based on the system behavior triggered by this DTC, owners and technicians can observe the following specific manifestations in driving experience and instrument feedback:

• No Charging Operation Possible: After entering the charging mode, the BMS (Battery Management System) or OBC rejects power transmission instructions.
• Abnormal Charging Indicator Status: Charging indicator lights on the dashboard or external vehicle body ports may display "Fault", "Charging Prohibited", or extinguish directly, unable to establish normal fast/slow charging connection indicators.
• AC Pile Recognition Failure: When connecting to a public charging pile, the charging pile display may prompt "Vehicle Not Supported" or "Communication Timeout", causing the handshake process to get stuck in the initial stage.
• Fault Code Storage and Lighting: The vehicle's self-diagnostic system (OBDII) will record this historical fault code. If not repaired, relevant indicator lights may remain lit and cannot be reset.
• Charging Interface Protection State Activated: Some models may automatically cut off the high-voltage interlock circuit to prevent forced power supply without confirming the charging protocol.

Core Fault Cause Analysis

According to the diagnosis data model, this fault is caused by hardware or logic anomalies in the following three dimensions, requiring comprehensive judgment combining physical connections and electronic architecture:

• Hardware Component End: Mainly involves Integrated Charging Port Fault or On-Board Power Supply Unit Internal Fault. This may include aging of CP detection circuit components inside the charging module, signal amplifier gain drift, or abnormal operation of dedicated detection chips on the OBC mainboard, causing it to fail in correctly parsing external analog voltage changes received.
• Wiring and Connectors End: Focus on investigating External Charging Connection Device Faults and Harness or Connector Faults. Since CP signals belong to high-frequency PWM signal transmission, damage to the cable's shielding layer, oxidation corrosion of pins, excessive contact resistance or loose connections (Loose Connection) will all cause voltage waveform distortion transmitted to the control unit, resulting in non-compliant duty cycle values at the sampling end.
• Controller Logic End: Involves the logical operation part inside the on-board power supply unit. If the controller's software calibration deviates, causing it to misjudge normal signal fluctuation range as "Beyond Threshold", or incorrectly triggers protection mechanisms under specific operating conditions (e.g., battery SOC near full), this fault code may be generated.

Technical Monitoring & Trigger Logic

The system's judgment of this DTC follows a strict Dual Monitoring Principle in Time Domain and Amplitude Domain, with the specific logic as follows:

• Monitor Target Parameters: Core indicator is the pulse width proportion of the CP signal, i.e., CP Duty Cycle. This parameter is continuously sampled during AC charging handshake.
• Fault Judgment Threshold Conditions: The system has clear electrical safety windows set. When the monitored CP Duty Cycle is outside the specified threshold, the logic judge will output a fault trigger signal. Here, "specified thresholds" are the upper and lower limits defined by the manufacturer's protocol communication standards to ensure the integrity of the charging handshake protocol.
• Dynamic Trigger Conditions: Monitoring mechanisms are activated only under Vehicle AC Charging Status. When a user inserts the charging gun and closes the grounding switch, if the system detects that the CP duty cycle signal continuously deviates from the specified range within preset sampling cycles, and the duration exceeds the diagnostic confirmation time set by the controller (usually several seconds to minutes), the OBC or Power Supply Unit will immediately interrupt the charging request and generate the fault code in the data stream.
• Trigger Logic Chain: Vehicle Power On -> Insert AC Charger -> Activate CP Signal Read Module -> Real-time Calculate Duty Cycle Ratio -> Compare with Specified Threshold -> Judge Result Abnormal -> Store Fault Code P159600.