Changan Eado EV Vehicle Fault Classification and Repair Process Guide

Fault Background

The vehicle fault repair manual for the Changan Eado EV classifies faults before troubleshooting: ①High-voltage output fault (no high voltage outside the battery pack, all air conditioning/driving/charging functions fail) ②Power interruption (cannot drive but air conditioning works) ③Power performance abnormality (can drive but power is reduced) ④Charging power limitation ⑤Charging abnormality ⑥Others. Two disciplines: On arrival, read fault codes from each controller and take photos, do not clear codes first; for vehicle diagnostics, read VCU codes first, then refer to component manuals as needed. The instrument cluster lights up in combinations based on fault type (high-voltage fault/power interruption/power performance abnormality/charging power limitation/charging abnormality), with observation timing varying from key ON to charging gun plugged in. This article is compiled as a repair guide.

On-Arrival Diagnostic Discipline and Fault Classification

1. Read codes on arrival: If no current fault but owner reports intermittent fault → read fault codes from each controller and take photos, do not clear codes first;
2. VCU priority: For vehicle fault diagnosis, read VCU controller fault codes first, follow this document; when referring to component troubleshooting, refer to the relevant component repair manual;
3. Six categories: High-voltage output fault / Power interruption / Power performance abnormality / Charging power limitation / Charging abnormality / Other types;
4. Instrument light observation timing: High-voltage fault, power interruption, power performance abnormality – check key ON position; Charging power limitation – check key OFF position; Charging abnormality – check charging gun plugged in state.

High-Voltage Output Fault

Symptom: No high-voltage output outside the battery pack – all high-voltage equipment fails: a) In-vehicle high-voltage equipment unusable (air conditioning cooling and heating); b) Vehicle cannot drive; c) Vehicle cannot charge. Must wear insulating gloves during troubleshooting.

Priority codes (non-charging state): 185 frame / 225 frame / 153 frame CheckSum verification fault / IPU frame / BCU frame verification fault – mostly intermittent in areas with severe electromagnetic interference; if cannot recover by power cycling and persists, request technical support directly; 12V undervoltage fault.

12V undervoltage troubleshooting chain: Recharge or replace auxiliary battery → Check high-voltage fault status at ON position → Measure voltage across auxiliary battery terminals with multimeter → Check whether DCDC output is normal → Check whether DCDC output harness is connected (replace output harness to ensure DCDC output to 12V battery positive is continuous) → After replacing DCDC, is auxiliary battery voltage 14V? → Check whether DCDC input high-voltage harness is properly seated → If still no 14V after reseating, replace connector or check for corrosion/oxidation. Repair verification: Positive and negative terminal voltage 14±0.5V indicates fault resolved.

Referrals: IPU level 3 fault → Read motor controller codes → Refer to "Motor System Fault Repair"; BMS level 4/5 fault → Read BMS codes → Refer to "Battery Management System Fault Repair".

HCU Communication Fault Four Families

BCU to HCU: First check BMS software version (cannot detect version = BMS not flashed) → Measure terminal resistance (if VCU terminal resistance abnormal, replace VCU; if BMS terminal resistance abnormal, replace BMS controller) → Check BMS constant power input (continuity from constant power to BMS pin) → Use multimeter to check continuity between VCU low-voltage connector pin 56 and BMS low-voltage connector pin 11 → Check continuity between VCU pin 37 and BMS pin 18, VCU pin 38 and BMS pin 9 → Clear VCU codes and power cycle → Replace BMS controller. Note: Before checking harness, check for backed-out terminals and ensure low-voltage connectors are secure; BMS controller is inside the battery pack and difficult to replace, so check it last.

IPU to HCU / IPU enable pin short to power: IPU enable relay damaged → Replace relay; VCU powerhold relay damaged → Replace relay; No continuity from relay output to IPU harness → Replace harness. Troubleshooting chain: At ON position, check whether powerhold relay output has 12V → Continuity between VCU pin 58 and powerhold relay enable terminal → IPU relay output 12V (if damaged, replace IPU relay; if still no output, VCU enable relay failed, replace VCU) → Harness from IPU relay to IPU pin 15 → Replace IPU → If still not recovered, request technical support.

SRS to HCU: CAN harness not continuous / SRS power harness not continuous. Troubleshooting chain: At key OFF, check whether OBD pins 6 and 14 resistance is 60Ω → After disconnecting VCU connector, check if 120Ω (BCM internal terminal resistor damaged → replace BCM; harness not continuous → replace harness) → After replacing VCU, resistance returns to 60Ω (if VCU issue, replace VCU) → SRS controller fault, replace SRS controller.

CHM to HCU: With charging gun plugged in, disconnect charger output harness and check → Check AC charging gun function (if the gun charges normally on another vehicle, gun issue can be ruled out) → Check voltage between charger input pins 1 and 3 → If high voltage present at charger input but not awakened → Replace charger → Check continuity between charger low-voltage connector pin 1 and OBD pin 3, and connector pin 2 to corresponding OBD pin.

Vehicle High-Voltage and Other High-Voltage Side Faults

• Vehicle high-voltage fault: First determine BCU software version is correct and corresponding (wrong software flash can cause VCU to misjudge high-voltage power-up failure) → Check short circuit between high-voltage harness positive and negative (if present, replace high-voltage harness) → Check continuity from BCU output to IPU high-voltage harness → Replace IPU → Remove battery pack and check high-voltage relay output inside pack to battery pack high-voltage output to high-voltage distribution box → Repair battery pack;
• BCU enable circuit fault (short to power): Replace VCU → Replace harness; Before replacing harness, use multimeter to check whether VCU connector pin 56 is shorted to power or continuity between pin 56 and BMS pin 11 – short = BMS enable pin short to ground fault (harness issue), open = BMS enable pin open circuit fault (harness issue);
• DCDC output harness short to ground: Check whether resistance between DCDC positive and negative is <1kΩ – if yes, harness short, replace harness → If still abnormal, replace DCDC;
• Collision fault: In a real collision, reading this DTC with a diagnostic scan tool is a necessary and sufficient condition; if code appears without collision – ①SRS controller false trigger (repair SRS per conventional vehicle methods) ②VCU hardwire false trigger (check harness for short to ground or open) ③BMS hardwire false trigger. Troubleshooting: Replace SRS controller → Power on and check if airbag indicator goes off (if not, replace collision detection sensors and related harness) → Check VCU and BMS hardwires receiving SRS collision signal for short/open (e.g., VCU low-voltage connector pin 20) → Clear VCU and BMS fault codes and power cycle.

High-voltage output fault resolution criteria: After clearing VCU codes and power cycling, no fault codes present + key ON, instrument READY indicator flashes green.

Power Interruption / Power Limitation / Charging Abnormality

Power interruption (cannot drive but air conditioning cooling/heating works): IPU level 2 fault → Motor system fault light illuminates, read motor controller codes and repair per manual; Accelerator pedal position sensor 1 short to power fault → Replace accelerator pedal assembly → Replace VCU → Check continuity between accelerator pedal pins and corresponding VCU pins; Gear position fault → Replace gear selector → Replace VCU → Check harness from gear selector to VCU.

Power performance limitation (can drive but power noticeably reduced): BMS level 3 fault → Refer to battery management system manual; HVAC-related fault causing power limitation → Refer to thermal management system manual; If IGBT overtemperature still reported after excluding HVAC → IPU internal IGBT damaged → Replace IPU assembly.

Charger fault or charger power limitation: This falls under high-voltage fault and system level 2 fault, and is also a step in charging abnormality troubleshooting – when customer reports inability to charge, troubleshoot per this table. Special note: Slower charging due to ambient temperature being too high or too low is normal. With key OFF and charging gun plugged in, connect diagnostic scan tool to charger to read current faults, then read VCU current faults and troubleshoot per table.

Key Parameter Quick Reference

Safety Warnings

• This article is for technical reference. For high-voltage troubleshooting, always wear insulating gloves; high-voltage harness measurements must follow high-voltage operation procedures.
• On arrival, take photos of fault codes before clearing – clearing history codes loses the "fault moment" evidence chain.
• Collision fault codes are a necessary and sufficient condition after a real collision – accident vehicles must follow accident repair procedures; strictly forbidden to clear codes and drive.
• Slower charging due to ambient temperature being too high or too low is normal; do not misdiagnose as a fault and replace parts.

Repair Insights

The most valuable part of this vehicle fault repair manual is "classification before troubleshooting": The instrument light observation timing for the five fault types varies (high-voltage/power interruption check ON position, charging power limitation check OFF position, charging abnormality check charging gun state) – first classify by symptom, then look at corresponding codes, avoiding searching for codes in the wrong system. Three measurement values form a vehicle-level rapid localization tool: OBD pins 6/14 60Ω/120Ω (one measurement distinguishes BCM terminal resistor, VCU, and harness issues), 14±0.5V (a one-vote veto indicator for DCDC system health), <1kΩ (threshold for DCDC output short to ground). The pin routing table is also worth copying: VCU 56→BMS 11 (enable), 37→18, 38→9 (CAN pair), VCU 58→powerhold relay, IPU 15 – these are the "point-to-point table" for harness checks; always check for backed-out terminals before measuring continuity. Finally, two disciplines are most easily overlooked: For verification faults in electromagnetic interference areas (185/225/153 frames) that cannot recover after power cycling, request technical support directly – do not repeatedly replace parts on the vehicle; For collision codes, first check "whether it is a real collision" – three paths: SRS false trigger, VCU/BMS hardwire false trigger; the order is always "airbag controller → sensor → hardwire".

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【This article is for reference only】