Dongfeng Fengxing S50EV Traction Battery Pack Diagnostics and Removal/Installation Guide

Fault Background

The traction battery assembly of the Dongfeng Fengxing S50EV (manual 1468) is mounted at the bottom of the vehicle, with a battery pack protective cover at the front underneath. The assembly is equipped with an MSD plug (S50EVB-2101401), coolant inlet/outlet ports, a low-voltage connector (TYCO 1-1564526-1), and a high-voltage connector. The three prerequisites for removal/installation discipline: ignition OFF → disconnect the 12V battery negative terminal in the engine compartment → pull the MSD plug; the battery pack is secured to the vehicle floor with 14 mounting bolts (1.5 thread pitch, grade 10.9) plus washers. The BMS has a total of 52 DTCs (B04/B34/U families), all organized as "three-part cause + step-by-step measures," with the core being a set of voltage/insulation dual thresholds: total voltage fault level 260~435.7V, warning level 312~431.6V; cell 3.0~4.2V (fault level) / 3.0~4.16V (warning level); insulation vehicle level 80kΩ (fault)/200kΩ (warning), pack level 2MΩ (GB/T 18384.1-2001 6.1.1). This article is compiled as a diagnostic and removal/installation guide.

Assembly Composition and Removal/Installation

Removal sequence: Rear seat U-shaped support bracket carpet → Open T-shaped support bracket carpet (4 bolts) → Open service access cover to see MSD → Pull MSD (press CPA button while pulling upward → rotate handle 90° to open) → Remove battery pack protective cover → Disconnect coolant inlet and outlet hoses (hoses usually contain coolant; use a container to catch it) → Disconnect high-voltage connector → Low-voltage connector (pry up yellow locking device and pull out harness side) → After lift fixture contacts battery pack bottom, use electric gun/socket to remove 14 mounting bolts and washers.

Installation reverse sequence: Battery pack assembly → Left/right ground copper straps → High/low-voltage harnesses → Coolant inlet/outlet hoses → Traction battery splash shield → Connect MSD (insert plug handle vertically → rotate handle until fully engaged → press CPA button → fully locked) → MSD ground wire bracket.

Storage discipline: Store removed battery assembly in a 10℃~28℃, ventilated, dry, clean indoor area, avoid impact, sunlight, rain; do not stack. Protect MSD plug/socket, water ports, and all interfaces from foreign objects and impact.

Low-voltage connector key points: High-voltage interlock input/output signals, IGN ON power (12V), main positive/main negative/precharge relay grounds (0V), main positive/main negative/precharge relay 12V power positive. Tools: Lift fixture (capacity ≥500kg), multimeter (voltage range ≥500V, error ≤1V), diagnostic scan tool (X431), megohmmeter (500V range).

Voltage and Cell Code Table (Threshold Matrix)

Temperature and Balance Codes

• B041900 / B042000 Temperature too high / too low (fault): Confirm sensor number via snapshot → measure temperature sensor resistance with multimeter: normal replace BMS, abnormal replace temperature sensor;
• B042100 / B042200 Temperature too high / too low (warning): With sufficient coolant and cooling system working, rest 30min and retest; if still reported, proceed with sensor resistance measurement;
• B042300 / B042400 Temperature deviation warning / fault: Park at room temperature for 24 hours (vehicle sleep) then restart and retest—if gone, it's actual temperature difference (areas facing heat/cold sources, insufficient coolant); if not gone, proceed with sensor resistance measurement.

Insulation Dual Thresholds and Relay Codes

Insulation (anode B042700 / cathode B042800, fault level): Disconnect battery pack high-voltage harness, measure vehicle insulation with megohmmeter—<80kΩ → check OBC/MCU/AC and other high-voltage components locate and replace one by one; >80kΩ → remove battery pack and measure per GB/T 18384.1-2001 6.1.1—>2MΩ replace BMS, <80kΩ replace battery pack. Warning level (B340012/013) vehicle threshold is 200kΩ, pack level 2MΩ.

Relay stuck (B340501 positive / B340601 negative): Turn off vehicle, pull out high-voltage connector from battery pack to PDU, measure voltage between positive and MSD positive (or negative and MSD negative) with multimeter—>10V replace high-voltage distribution box, no voltage replace BMS.

12V lead-acid battery (B043500 too high / B043600 too low): Measure lead-acid voltage under hood—>16V or <9V → replace lead-acid battery and check DCDC; 10~15V → replace BMS.

CAN Communication Family and Charging Codes

CAN binary method (U240101 high-voltage acquisition module / U012200 VCM / U011000 MCU / U019B00 slow charger / U240201 current sensor / U029800 DCDC / U240301 slave communication lost): Use CAN communication device to check if corresponding node on EV_CAN sends signal—signal present → BMS internal circuit fault, replace BMS (or master/slave); no signal → check CAN wiring and corresponding controller status; if harness not conductive, replace harness.

Charging types: B043700 slow charging fault (check OBC/VCM); B043800 fast charging fault (retest with another EVSE, if still reported check VCM); B042500/B046300 charging current too high (after unplugging and sleep, retest with portable charger, if still reported replace current sensor); B042600/B046500 discharging current too high (retest with all electrical loads off and high voltage on, do not allow aftermarket high-voltage loads); B043200/3300 overcharge/discharge amount (replace portable charger; monitor voltage and current with oscilloscope, product 1.5 times ≤ max allowable power judge BMS); B043900 collision fault (do not use if appearance has defects); B043400 battery pack degradation (replace within warranty).

Post-Repair · Battery Pack Offline Configuration

Battery heating system is optional: after replacing new battery pack, write "whether battery heating system is configured" into battery pack (program default has heating configuration). Diagnostic scan tool path: "China"→"Dongfeng Fengxing (Special)"→ S50EV EV → Battery Pack Management System (BMS) → Offline Configuration → Battery Cooling Device Configuration—if vehicle has battery heater, click "Yes" to write configuration info; prompt "Configuration Successful" means complete; prompt "Configuration Failed" requires reconfiguration.

Safety Warnings

• This article is for technical reference. Traction battery inspection is high-voltage work; must be performed by qualified technicians (electrician certificate + company training authorization) per OEM specifications.
• Three prerequisites are indispensable: ignition OFF → disconnect 12V negative → pull MSD; wear insulating gloves throughout removal/installation; use container to catch coolant when removing hoses.
• Insulation testing per two-level thresholds (vehicle 80kΩ/200kΩ, pack 2MΩ per GB/T 18384.1-2001); battery with appearance defects after collision must not be used.
• Disposal: major impact (e.g., traffic accident) with deformation return to factory for repair; severe deformation scrap.

Repair Insights

The S50EV battery code table uses "responsibility binary method" to the extreme; the most worth memorizing is insulation dual thresholds: vehicle level 80kΩ (fault)/200kΩ (warning) first cut "external high-voltage components" vs "inside battery pack"—below threshold, locate OBC/MCU/AC one by one, avoiding unnecessary battery pack removal; after passing vehicle level, use GB/T 18384.1-2001 2MΩ pack-level threshold to cut "BMS detection circuit" vs "battery pack itself". Voltage codes use "fault/warning dual level + symmetric window": total voltage 260~435.7V (fault) and 312~431.6V (warning) two windows, cell 3.0~4.2V and 3.0~4.16V two windows—warning level first adjust SOC (charge/discharge to 50%) before acting, fault level directly measure with multimeter to judge BMS or battery pack. Two easily overlooked details: relay stuck judged by "voltage between positive and MSD positive >10V"—no need to disassemble high-voltage box; new battery pack must do "battery cooling device offline configuration"—default has heating configuration, missing configuration will cause false heating fault on non-heated models. Finally, patience with deviation codes: small current repeated charge/discharge + rest 30min (voltage deviation) and room temperature parking 24 hours (temperature deviation) both give system self-healing opportunity first.

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【This article is for reference only】