Changan Eado EV Power Supply System Assembly OBC Fault Diagnosis and Disassembly Guide

Fault Background

The power supply system assembly of the Changan Eado EV (C211-EV) is a two-in-one unit combining the OBC and DCDC: after power-on initialization, it charges the traction battery according to CAN bus charging parameter commands (charging mode), or supplies power to AC loads according to CAN bus discharging parameter commands (discharging mode). Internally, it contains a 2kW DCDC auxiliary power supply and DSP control. The assembly interfaces are divided into four categories: AC input, high-voltage DC output 1 (PTC positive/negative + air conditioning compressor positive/negative), high-voltage DC output 2 (high-voltage DC positive/negative + high-voltage interlock), and low-voltage connector (OBC/DCDC low-voltage input, HVIL, hard-wire wake-up, indicator light output). Fault codes are concentrated in the P1A8x family (12V voltage, CP internal 6V/9V/frequency/duty cycle, charge/discharge voltage shutdown). The troubleshooting routine is fixed: reconnect slow charging → VCU clears history DTCs and reads current DTCs → live data/connector/wiring harness → replace assembly. This article is organized as a maintenance guide.

Working Principle and Interfaces

Dual modes: ① Charging mode—charges the traction battery according to CAN charging parameter commands; ② Discharging mode—supplies power to AC loads according to CAN discharging parameter commands. Internally, the assembly consists of OBC + 2kW DCDC auxiliary power supply + DSP control.

Interface layout:

• AC input connector: phase line / neutral line / ground (PE);
• High-voltage DC output connector 1: PTC positive / PTC negative / air conditioning compressor positive / air conditioning compressor negative;
• High-voltage DC output connector 2: high-voltage DC output positive (A high-voltage interlock) / high-voltage DC output negative (B high-voltage interlock);
• Low-voltage connector: OBC low-voltage input positive ×2, DCDC low-voltage input positive, high-voltage interlock positive HVIL+ / high-voltage interlock negative, DCDC hard-wire wake-up, indicator light output LEDI-12V, wakeup hard-wire wake-up output, OBC/DCDC low-voltage input negative, indicator light output GND.

Torque specifications: Assembly mounting bolts 4×M8 (hex flange); wiring harness fixing bolts 2×M6.

P1A8x Code Family (OBC Side)

General troubleshooting process: Correctly connect the slow charging device and recharge → use diagnostic scan tool to enter VCU, clear history DTCs, and read current DTCs → if not reproduced, no action; if reproduced → use diagnostic scan tool to read live data (related to power supply system assembly) → vehicle power-down, check assembly connector → replace wiring harness and retest → if still reproduced, replace power supply system assembly.

Disassembly and Assembly Discipline

Three safety disconnections: ① High voltage must be disconnected before disassembly/assembly; ② Ensure charging gun is in non-connected state; ③ Turn key to OFF position and remove service disconnect switch before operation.

Prohibition: Do not disassemble the upper cover of the power supply system assembly (internal is a non-serviceable unit).

Assembly sequence: Assembly is fixed to bracket with 4 hex flange bolts → 1 hex flange bolt connects ground wire → 1 hex flange bolt connects low-voltage DC output positive wire → fix coolant hose → fix wiring harness. Disassembly is reverse order; after all installation is complete, perform bleeding and replenish coolant. During disassembly/assembly, bolts must be tightened to specified torque to ensure assembly reliability.

Key Parameter Quick Reference

Safety Warnings

• This article is for technical reference. The power supply system assembly is a high-voltage component; disassembly/assembly should be performed by technicians trained in high-voltage procedures, wearing insulating gloves.
• Before disassembly/assembly, high voltage must be disconnected, charging gun confirmed non-connected, key OFF, and service disconnect switch removed.
• Do not disassemble the assembly upper cover—the internal OBC/DCDC is a sealed service unit; opening the cover voids warranty and safety rating.
• After installation, bleeding and coolant replenishment are mandatory to avoid localized air pockets causing overheating shutdown.

Maintenance Insights

The most distinctive feature of this power supply chapter is "assembly-level repair": the diagnostic trees for the 12 P1A8x codes almost all converge to "replace the power supply system assembly"—CP internal 6V/9V/frequency/duty cycle abnormalities (P1A82~P1A85) directly indicate board-level damage with no repair path, and the manual uses "two rounds of clearing and retesting" to rule out intermittents before replacement. The only codes truly worth troubleshooting are the charging output/input shutdown family (P1A86~P1A8A): read live data to determine whether the issue is on the input or output side, then perform vehicle power-down and check the assembly connector and wiring harness—among these four codes, intermittent connection in the harness is genuinely repairable. The most easily overlooked of the three safety disconnections is "charging gun non-connected state": disconnecting high voltage but not the gun leaves CP/CC levels at the port, potentially allowing operation with voltage present during assembly removal. Finally, note assembly details: ground wire and low-voltage DC output positive wire each use 1 bolt—incorrect torque on the positive wire bolt can cause voltage drop and heat generation, making it one of the two hottest points at the assembly end.

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【This article is for reference only】