Geely Emgrand EV Pro Electric Drive System Fault Diagnosis and Replacement Guide

Fault Background

The electric drive system of the Emgrand EV Pro consists of an integrated power unit (IPU), a permanent magnet synchronous motor, and a single-speed reducer: the IPU uses field-oriented control (FOC) to invert the DC bus voltage into three-phase symmetrical current, and the motor output shaft is coaxial with the reducer input shaft, directly connected to the half shafts. Maintenance of this system follows two main lines: power faults follow the "three-fuse check" (CF27/EF32/EF19), internal faults follow DTC trigger conditions—the manual lists the trigger thresholds (temperature range, current threshold, voltage window) for each fault code. This article compiles the working principle, power diagnosis routine, DTC key points, and replacement torque into a field guide.

System Working Principle Overview

• Motor controller (IPU): Based on the detected motor speed and reference speed, the speed regulator obtains the target torque; the stator phase current is transformed to a two-phase coordinate system via Clarke transformation and to the d-q rotating coordinate system via Park transformation, compared with the reference current, and the current controller outputs the control quantity, which is then sent to the SVPWM inverter via inverse Park transformation to control the three-phase symmetrical winding current of the stator.
• Permanent magnet synchronous motor: Three-phase AC current is applied to the stator three-phase windings to generate a rotating magnetic field. Relying on the attraction of opposite poles and repulsion of like poles, the stator rotating magnetic poles drag the permanent magnet rotor to rotate synchronously.
• Reducer: The motor speed-torque characteristics suit vehicle drive requirements; pure electric mode no longer needs a multi-gear transmission; the reducer is between the drive motor and the drive half shafts, with the motor power output shaft coaxial with the reducer input shaft.

Routine Checks and Diagnostic Preparation

Before diagnosis, perform four routine checks: ①Check for aftermarket add-on devices that may affect the electric drive system; ②Check easily accessible or visible components for obvious damage; ③Check the exterior of the electric drive system for water or foreign objects; ④Check high-voltage wiring harness connectors for looseness and internal corrosion signs.

Diagnostic system key points: OBD regulations require that when a component fault is detected, the instrument fault lamp illuminates and the DTC is recorded; if the fault does not recur within 3 consecutive drive cycles, the fault lamp goes out automatically, but the DTC remains stored in the control module memory. If the diagnostic scan tool communication is abnormal, first verify whether it is a vehicle diagnostic interface issue or a scan tool issue by testing on another vehicle. Before troubleshooting, read the live data stream and perform actuator function tests (check relay and actuator status without disassembling parts), and compare reference values with a normal vehicle under the same conditions.

Integrated Power Unit Power Fault Diagnosis

DTC setting conditions: No low-voltage sensor fault detected, or low-voltage ≤5.26V / ≥5.29V.

Diagnostic steps:

1. Visually inspect the integrated power unit (damage, deformation, stains, looseness) and wiring harness connectors (damage, poor contact, aging, looseness);
2. Measure battery voltage: with ignition ON, use a multimeter, standard 9~16V; if abnormal, replace the battery or repair the charging system;
3. Three-fuse check: with ignition OFF, remove interior fuse CF27 (15A), front compartment fuses EF32 (15A) and EF19 (7.5A); if any is blown, repair the fuse circuit and replace with a fuse of the same rated capacity;
4. Check controller power circuit: with ignition OFF, disconnect the integrated power unit wiring harness connector BV45; with ignition ON, measure terminal voltages per the table;
5. Check controller ground circuit: with ignition OFF, disconnect BV45, measure terminal-to-ground standard resistance less than 1Ω;
6. Replace the integrated power unit, reprogram and configure (refer to module programming and setup);
7. Clear DTCs with the diagnostic scan tool → road test the vehicle for at least 10 minutes → read fault codes again to confirm no output.

DTC List and Key Trigger Conditions

General diagnostic routine for internal faults: Use the diagnostic scan tool to confirm the DTC is stored again (road test in READY mode for at least 10 minutes, then read codes) → visually inspect the controller and wiring harness → reprogram and configure → if still abnormal, check power/ground, then replace the integrated power unit → reprogram and configure again → clear codes and road test for at least 10 minutes to confirm elimination.

Communication faults have an extra step: first check HB-CAN network integrity; if the network is abnormal, repair the CAN bus or replace the wiring harness; only if the network is normal, replace the controller.

Assembly and Controller Replacement Torque

Disassembly/assembly key points: Electric drive system assembly removal follows the sequence "disconnect DC bus → remove left/right constant velocity drive shafts → water pump/compressor/ground → engine mounts → steering gear/stabilizer bar/control arm/tie rod → subframe"; subframe mounting bolts must be replaced with new ones each removal. For drive motor controller replacement, first remove the electric drive system assembly, then remove the power wiring harness cover, inverter-to-oil-cooler water pipe clamp, vent cover and three-phase copper busbar, and finally remove the controller mounting bolts. For oil cooler replacement, coolant must be drained first, prevent mixing of coolant and lubricating oil; the reducer oil seal left and right sides are similar (special tool numbers 414720088, 4114720089).

Safety Warnings

• This article is for technical reference; high-voltage repairs must be performed by certified personnel according to OEM specifications; readers unfamiliar with the procedures are strictly prohibited from performing operations themselves.
• The electric drive system can only be disassembled/assembled after disconnecting the DC bus assembly; do not perform live operations when checking high-voltage wiring harness connectors for looseness and corrosion.
• Subframe mounting bolts must be replaced with new ones each removal and tightened to the specified torque of 120N·m; mount-type bolts must be tightened in stages (70/90/210N·m).
• After replacing the integrated power unit, reprogramming and configuration are mandatory, and a road test of at least 10 minutes must be performed to confirm fault elimination before returning the vehicle.
• Fuses must be replaced with the same rated capacity (CF27/EF32 15A, EF19 7.5A); never increase the capacity.

Maintenance Insights

The Emgrand EV Pro electric drive system manual's greatest gift to field technicians is turning fault codes into "measurement problems" rather than "guessing games": each DTC comes with trigger conditions—temperature falling in 146.5~151°C indicates IGBT module Level1 over-temperature, 151~155°C indicates Level2; single-phase current zero-drift exceeding 47.24A reports zero-drift fault, exceeding 770.69A reports overcurrent; KL30 voltage must fall within the 8.44~16.9V window for diagnosis to be valid. Understanding these numbers allows you to judge before acting whether it is a sensor false alarm or a real fault. Two process experiences are equally valuable: for power faults, first check the three fuses (CF27/EF32/EF19), then check BV45 terminals and ground resistance less than 1Ω—half of the "controller failures" actually die on fuses; after replacing the controller, "programming + road test for at least 10 minutes" dual confirmation is mandatory—if you return the vehicle without programming, anti-theft (ESK/IMMOCode) will immediately call you back.

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【This article is for reference only】