Changan BenBen EV Vehicle Electronic Control System Fault Diagnosis Guide

Fault Background

The Changan BenBen EV (1781 manual) vehicle electronic control system consists of three major components: IPU (integrated motor controller and DCDC), on-board charger (OBC), and thermal management system controller, with VCU for overall coordination. The manual classifies vehicle faults into three levels: Level 1 faults (e.g., P1841) linearly reduce power and can recover automatically; Level 3 faults (e.g., P1842) directly result in no output power, complete vehicle high-voltage power-down, and require repair. The core diagnostic weapons are a set of hard thresholds: high-voltage components to chassis ground insulation ≥20MΩ, battery pack voltage window 220~430V, grid voltage window 80~273VAC, auxiliary battery 9~16V, wiring harness open circuit <1Ω / short circuit ≥10MΩ. This article organizes fault codes and troubleshooting paths in the order of "motor system → DCDC → OBC → thermal management".

Motor System (IPU) Fault Classification and Troubleshooting

Fault levels: P1841 = IPU Level 1 fault (linear power reduction, can recover automatically, no repair needed); P1842 = IPU Level 3 fault (no output power, complete vehicle high-voltage power-down, repair required).

Level 2 fault code table (common items): CAN communication timeout, P094C motor overspeed, P094D motor over-temperature, P1908 motor temperature too low, IGBT over-temperature, bus voltage under-voltage, bus voltage over-voltage, motor torque error, discharge fault, IGBT temperature sensor rationality error, A-phase/C-phase AC sensor rationality error.

Troubleshooting path (shared for power-type faults: power module fault/motor overcurrent/DC current sensor rationality error):

1. Re-power on and read codes to reproduce the fault;
2. Check whether the IPU three-phase power line quick connectors and high-voltage connectors are loose;
3. Use an insulation tester to measure insulation resistance between the three-phase power line terminals and chassis ground: <20MΩ replace IPU; ≥20MΩ proceed to next step;
4. Lift the vehicle, open the motor three-phase power line junction box cover to check for water ingress, and measure insulation to ground for the harness side and motor U/V/W terminal block separately: harness side <20MΩ replace the three-phase power harness, motor side <20MΩ replace the motor.

Resolver and temperature type: Unplug the IPU 39-pin and motor end 8-pin connectors to check for backed-out or bent pins; use a multimeter to measure at the motor end pins 1-2 = 27±2.7Ω, pins 3-4 = 60±6Ω, pins 5-6 = 64±6.4Ω (three resolver windings); pins 7-8 = 1±0.2kΩ (motor temperature sensor).

Over-temperature type (motor over-temperature/IGBT over-temperature): First check the water pump (hand vibration) and coolant level (above the scale line), run for 10 minutes and re-observe; if water pump fault, check the pump; if low on coolant, refill; if water pump and coolant are normal but still over-temperature → replace IPU.

Bus voltage type: Under-voltage—read vehicle live data stream, if voltage below 240V first charge the vehicle, otherwise replace IPU; Over-voltage—if code appears during charging, stop charging, clear codes and re-test; if code appears during driving, first check whether DCDC input or battery management system reports over-voltage; if battery system over-voltage, first troubleshoot battery side, otherwise replace IPU.

DCDC Module (Built into IPU) 12 Faults

All fault levels are Level 1, total 12 items: output over-temperature, recoverable fault (no troubleshooting needed), unrecoverable fault, input under-voltage (refer to bus under-voltage), input over-voltage, output under-voltage, output over-voltage, output short circuit, output overcurrent, output over-temperature, over-power output, hardware fault, no vehicle CAN communication received.

Key points: Output under-voltage/short circuit/overcurrent—disconnect the auxiliary battery positive cable and the DCDC output connector, measure for short circuit between positive and negative lines; if short circuit, find the short point; if no short circuit, replace IPU; Output over-temperature—water pump/coolant check same as IPU over-temperature; if water pump and fan are normal and coolant is full but still reports over-temperature → replace IPU; Input over-voltage—if code appears during charging, stop charging, clear codes and re-test; if code appears during driving, first check IPU input or battery management system over-voltage; most other items directly replace IPU.

Fuse configuration: DCDC fuse 10A, air conditioning compressor fuse 30A, PTC fuse 30A.

Charger (OBC) Fault Troubleshooting

Fault levels: P1841 = OBC recoverable fault (no repair needed); P1842 = OBC unrecoverable fault (repair required). Total 19 troubleshooting items, core is "change charging station and re-test + threshold boundary determination":

Low-voltage connector key points: Low-voltage input positive KL30 (12V/1A), indicator light output LED (12V/50mA), hardwire wake-up output HW_WAKEUP, control pilot CCP, high-voltage interlock HVIL-; AC input connector model 1587973-1, high-voltage DC output connector 2103124-4.

Thermal Management System B140x Code Table (Air Conditioning System)

Universal five-step diagnosis: ①Visual inspection of related harness connectors (damage/poor contact/aging/loose); ②Use diagnostic scan tool to clear codes, then re-read after ignition operation; if no codes, it is an intermittent fault; ③Open circuit check (resistance standard between related terminals <1Ω); ④Short circuit check (resistance standard between terminals ≥10MΩ); ⑤Power short circuit check (signal terminal to reliable ground voltage standard 0V; water pump power terminal to ground 12V). If harness abnormal, replace corresponding harness; if harness normal, replace sensor/actuator (for water pump type, replace water pump); if still abnormal, finally replace thermal management system controller assembly (connector E23).

Safety Warnings

• This article is for technical reference only. High-voltage system (IPU/OBC/traction battery) repair must be performed by qualified professional technicians (electrician certificate + company training authorization) according to OEM specifications. Before operation, ensure complete vehicle power-down and confirm no residual voltage on the high-voltage bus.
• Insulation tester measurements, three-phase power line removal/installation, and other high-voltage operations require insulated gloves and qualified insulated tools.
• For lifting operations, confirm the lift safety locks; after disconnecting the auxiliary battery negative cable, begin harness measurements.
• If voltage-related faults occur during charging, stop charging first before troubleshooting; strictly prohibit disassembling high-voltage connectors while powered.

Maintenance Insights

The most valuable code table for the BenBen EV is the "20MΩ three-segment positioning method": for power-type faults, measure all the way—IPU side <20MΩ replace IPU, harness side <20MΩ replace harness, motor side <20MΩ replace motor, with clear boundaries and no disputes. For OBC, it is "change charging station and re-test + threshold boundary determination": for CP-type abnormalities, first change charging station to rule out external factors; for voltage-type, directly use the three windows of 220/430V, 80/273VAC, 9~16V to assign responsibility—if outside the window, first check battery/grid/auxiliary battery; only if within the window, replace OBC, avoiding unnecessary replacement of expensive parts. Thermal management B140x all follow the same template: <1Ω for continuity, ≥10MΩ for open circuit, 0V for power short circuit, and only as the last step replace the thermal management system controller assembly. Remember the fault level discipline: Level 1 recoverable faults can be observed; only Level 3 unrecoverable faults require repair—first classify, then troubleshoot.

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【This article is for reference only】