Geely Emgrand EV Pro Charging System Tri-Integrated Fault Diagnosis and Replacement Guide

Fault Background

The Emgrand EV Pro's charging system is a "tri-integrated" deep integration structure: OBC (on-board charger), DC/DC, and PDU (power distribution unit) are made into one high/low-voltage charging system assembly, plus an independent high/low-voltage converter (dual-integrated). It manages not only plug-in charging (fast/slow charging) but also three types of "internal charging": low-voltage power charging, smart charging, and regenerative braking energy feedback. When troubleshooting, the manual follows three lines: "power fault → communication fault → internal fault," each with fuses, terminal voltages, and DTC trigger thresholds. This article compiles the working principle, diagnostic approach, DTC thresholds, and replacement torque into a field guide.

System Working Principle (Five Charging Modes)

1. Fast Charging (DC Charging): Charging gun connects to the vehicle's DC charging port → DC charging equipment sends a charging wake-up signal to the BMS → BMS self-check passes and receives charging connection confirmation signal and charging messages → Closes fast-charge relay and main negative relay to start charging → After completion, BMS sends stop command to the charging pile, and after the pile stops, the relays are opened. 153Ah battery can charge 30%~80% in 0.5 hours.
2. Slow Charging (AC Charging): VCU is woken by OBC, receives AC charging connection confirmation signals (CC, CP) from OBC, BMS high-voltage interlock status is closed, SOC<100%, and vehicle EPB or P gear is locked → Sends charging permission signal to BMS → BMS closes main positive relay and main negative relay to start charging → After OBC receives VCU AC charging command, its internal DC/DC charges the battery → After completion, VCU stops DC/DC and commands BMS to open main relays.
3. Low-Voltage Charging: After high-voltage power-on, the built-in DC/DC in the high/low-voltage charging system converts the traction battery's high-voltage DC to low-voltage DC, charging the 12V lead-acid battery and serving as auxiliary low-voltage power supply.
4. Smart Charging (Smart Replenishment): When low-voltage battery voltage drops below set value, BMS sends smart replenishment request to VCU; VCU receives power mode OFF and confirms four doors and two covers closed, then commands BMS to close main relays; after main positive and negative relays close, DC/DC starts charging the battery—preventing low-voltage battery drain and no-start after long-term parking.
5. Energy Regeneration: During coasting or braking, VCU calculates required braking torque and sends to motor controller; motor switches to generator mode to charge the battery pack; motor converts wheel kinetic energy to AC, then motor controller converts to DC to charge the traction battery.

Interface locations: AC charging port is on the left front side of the vehicle, DC charging port is on the left rear side, both mechanical unlock, push-push type; after connection, a detection loop is formed, and connection faults can be detected by the system.

Fault Symptom Table and Diagnostic Approach

All items share the same ending: Replace module → Reprogram and set up → Clear codes with diagnostic scan tool → Road test at least 10 minutes → Read codes again to confirm no output. For communication faults, there is an extra step before replacement: Check HB-CAN network integrity; if network abnormal, repair CAN bus or replace wiring harness.

Power Fault Diagnosis

High/low-voltage charging system power fault (tri-integrated):

1. Visual inspection of assembly and harness connectors (damage, deformation, dirt, looseness);
2. Measure battery voltage, standard 9~16V, if abnormal replace battery or repair charging system;
3. Fuse check: In OFF state, remove front compartment fuses EF18 (7.5A), EF33 (10A); if blown, repair circuit and replace with same rated fuse;
4. Disconnect high/low-voltage charging system harness connectors CA273, CA272a, in ON state measure power terminal, standard voltage 14V;
5. Disconnect BE16 (DC-DC negative harness connector) and measure ground terminal, standard resistance less than 1Ω;
6. Replace high/low-voltage charging system → Reprogram and set up → Clear codes, road test at least 10 minutes to confirm.

High/low-voltage converter power fault (dual-integrated) (DTC trigger: controller supply voltage low/high; U300617 voltage >16.2V for 500ms; charger handle wake-up detected—CC/CP connection or NM or KL15):

1. Visual inspection of converter and harness connectors;
2. Battery voltage 9~16V;
3. Fuse check: EF48 (150A), EF33 (10A), EF18 (7.5A);
4. Disconnect CA292, CA293, in ON state measure power terminal, standard voltage 11~14V;
5. Disconnect BE16 and measure ground <1Ω;
6. Replace high/low-voltage converter → Reprogram and set up → Clear codes, road test at least 10 minutes.

DTC List and Key Trigger Conditions

High/low-voltage charging system internal fault (tri-integrated):

High/low-voltage converter internal fault (dual-integrated):

Communication DTCs: U012187 lost BMS (ID=0x21) message for 1000ms; U11487 lost VCU (ID=0x161) information for 250ms; U007300 bus off (CAN bus disconnected)—detection conditions are CAN bus node power 9~16V, ignition on.

Replacement Points and Torque

Safety Warnings

• This article is for technical reference only; high-voltage repairs must be performed by certified personnel per OEM specifications; readers unfamiliar with such work are strictly prohibited from attempting it themselves.
• When replacing the tri-integrated assembly or dual-integrated converter, always disconnect the battery negative, disconnect the DC bus, and drain/fill the traction battery coolant.
• Fuses must be replaced with same rated capacity (EF18 7.5A, EF33 10A, EF48 150A); never increase capacity.
• After module replacement, reprogramming and setup are mandatory, and a road test of at least 10 minutes is required to confirm fault elimination before returning the vehicle.
• When temperature-related DTCs for charging port or gun (e.g., gun temp >110°C) appear, first inspect charging equipment and interface contact; avoid continuing charging while hot.

Repair Insights

The Emgrand EV Pro charging system hardwires the "charging routes": external fast/slow charging and internal low-voltage charging, smart replenishment, and energy regeneration—five routes share one relay logic—fast charging only closes fast-charge relay + main negative; slow charging closes main positive + main negative; smart replenishment requires dual conditions of "OFF mode + four doors and two covers closed." The three most useful numbers for troubleshooting: the 9~16V and <1Ω baselines for power diagnosis (tri-integrated and dual-integrated each have their own fuse set: EF18/EF33 for tri-integrated, EF48/EF33/EF18 for dual-integrated); PFC bus 450V overvoltage shutdown + 5-second self-recovery (this distinguishes real faults from grid fluctuations); DC/DC power level defined by external resistor (2kΩ=3.3kW, 1kΩ=6.6kW; if power is wrong after replacement, check this first). Also, don't forget the old rule: after module replacement, programming + 10-minute road test are both essential.

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【This article is for reference only】