Chang'an Plug-in Hybrid On-Board Charger (OBC) Fault Diagnosis and Removal/Installation Guide

Fault Background

The on-board charger (XCHA02) of the Chang'an plug-in hybrid (777 manual) uses the same topology as the CS15EV—Inrush current limiting (thermistor + resistor) → EMI filter → continuous interleaved PFC → full-bridge isolated conversion → high-voltage output—with DSP master control coordinating PFC/full-bridge isolated conversion/current control, communicating with the BMS via isolated optocoupler CAN, and featuring a battery detection circuit to prevent charger faults when the battery is not connected. However, the thresholds differ from the CS15EV: output overvoltage shutdown at 455±5V, output undervoltage shutdown at 165±5V, input overload at 16A, output overload at 12A—due to the different battery pack voltage platform of the plug-in hybrid. The low-voltage connector has an additional pair of high-voltage interlock HVIL+/HVIL- pins compared to the CS15EV. DTCs P1A80~P1A92 plus U12B0~B2 total 21 codes, with a unified handling mode. This article is organized as a diagnostic and removal/installation guide.

Connector and Torque Specifications

Low-voltage connector: control pilot CP, indicator light output LED×2 (+12V/50mA), low-voltage input positive KL30 (+12V/1A), hard-wire wake-up output HW_WAKEUP, high-voltage interlock HVIL+/HVIL-, indicator light output ground LED_GND, low-voltage input negative KL31_GND. High-voltage DC output terminals are divided into positive and negative poles (B terminal is negative).

Torque specifications: charger upper cover mounting bolts (No. 3 star hex) ×11; lower cover mounting bolts (No. 3 star hex) ×23—non-professionals are not allowed to remove the charger upper cover.

DTC Quick Reference (21 Codes)

Unified handling mode: correctly connect the slow charging device and recharge → use the diagnostic scan tool to enter the VCU and clear history DTCs → read current DTCs → judge according to the table.

Key points: P1A89/P1A8A check the charging voltage window (455V/165V), P1A8B/P1A8C check the grid window (80VAC/273VAC), P1A90/P1A91 check current (16A/12A)—outside the window, replace the charger; inside the window, first check the corresponding external system, then clear codes and retest.

Removal/Installation Procedure (Subassembly + Tray Assembly)

Safety prerequisites: ① Cut off high voltage; ② Charging gun not connected; ③ Key in OFF position + remove the service disconnect switch, then proceed.

Installation four steps (subassembly structure):

1. Secure the charger assembly to the charger bracket with 4 hex flange bolts; secure the charger ground wire to the charger ground point with 1 hex flange bolt to complete the subassembly;
2. Install the subassembly onto the charger tray—the bracket snaps into the tray's retaining slot, then secure with 2 hex flange bolts;
3. Secure the coolant hoses firmly;
4. Secure all connectors firmly.

Removal: Reverse the procedure; after all installation is complete, bleed the cooling system and top up coolant.

Tools: diagnostic scan tool, digital multimeter, insulating gloves, megohm meter, torque wrench.

Safety Warnings

• This article is for technical reference only. Charger removal/installation involves high voltage and coolant, and must be performed by qualified technicians (electrician certification + company training authorization) in accordance with OEM specifications.
• All three prerequisites are mandatory: high voltage off, charging gun not connected, key OFF + service disconnect switch removed; after reassembly, bleed and top up coolant.
• The 11 upper cover / 23 lower cover bolts are No. 3 star hex, operate with specified torque; non-professionals are not allowed to remove the upper cover.
• When measuring grid voltage, take precautions against live parts; check insulating gloves for leaks before use.

Maintenance Insights

The plug-in hybrid's OBC DTC table shares the same origin as the CS15EV but with different thresholds. When repairing, first confirm the vehicle platform, then consult the table: the CS15EV is 430V/220V, 12A/12A, while the plug-in hybrid is 455V/165V, 16A/12A—the output window is nearly twice as wide, indicating the PHEV battery pack has a higher voltage platform and a higher slow-charge input current limit. The method of memorizing the windows remains the same: voltage codes check charging voltage, grid codes check outlet voltage, overload codes check current—outside the window, decisively replace the charger; inside the window, first check the battery/grid/harness, then fall back to the logic of "clear codes and retest still reports → replace charger." Two new details: the low-voltage connector has an additional pair of HVIL+/HVIL-—the plug-in hybrid's charger is integrated into the vehicle's high-voltage interlock loop; an open interlock will directly prevent charging, so when troubleshooting charging faults, first confirm these pins; the removal/installation uses a "subassembly" structure—the charger + bracket + ground wire are first assembled as a subassembly, then the whole unit snaps into the tray's retaining slot; when removing, do not pry the tray's retaining slot, just reverse the procedure. The temperature code P1A8E troubleshooting chain (coolant level → water pump → live data) is consistent with the CS15EV and can be applied directly.

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【This article is for reference only】