Roewe Plug-in Hybrid Low-Voltage Wiring Harness and EDU Harness Replacement Guide

Fault Background

The low-voltage wiring harness replacement for the Roewe plug-in hybrid (1012 manual) is essentially a "51 connection points + ground points" work list: the engine compartment harness runs from the right front headlamp all the way to the BCM in the passenger compartment, and each ground point must be operated in pairs as "loosen/tighten"—if you miss a ground point during harness troubleshooting, you are planting a new intermittent fault. Running parallel to the low-voltage harness, the electric drive transmission (EDU) harness is high-voltage peripheral work, and the manual gives high-voltage discipline: Personnel not trained on this vehicle's high-voltage system are prohibited from disassembling high-voltage components; when removing or installing high-voltage parts, the 12V power supply and the manual service disconnect on the traction battery must be disconnected; after turning off the ignition key, wait at least 5 minutes (the high-voltage capacitors in the power electronics box need time to fully discharge). This article organizes the low-voltage harness replacement sequence and high-voltage harness work discipline into a guide.

High-Voltage Work Safety (Around the EDU Harness)

1. Training threshold: Personnel not trained on this vehicle's high-voltage system are prohibited from disassembling high-voltage components (traction battery, electric drive transmission, power electronics box, high-voltage harness, electric A/C compressor, on-board charger, AC charging port, and AC charging cable);
2. Dual power-off: When removing or installing high-voltage parts, the 12V power supply and the manual service disconnect on the traction battery must be disconnected;
3. Personal protective equipment: Wear protective gear before work—insulated gloves, high-voltage insulated shoes; check insulated gloves for damage before each operation to ensure they are not compromised;
4. Fluid protection: Prevent brake fluid, windshield washer fluid, coolant, and other liquids from entering or splashing onto high-voltage components during installation and removal;
5. Wait for discharge: Turn off the ignition key and let the vehicle sit for at least 5 minutes before removal or installation—high voltage remains present after the ignition is off (energy stored in the high-voltage capacitors of the power electronics box), so wait for the capacitors to fully discharge;
6. Installation discipline: Before the high-voltage system is fully installed (including all connector mating), ensure the battery negative cable is disconnected and the manual service disconnect is in the open position.

Engine Compartment Harness Replacement (51-Step Sequence)

Removal sequence (grouped by area):

1. Disconnect negative terminal → remove manual service disconnect → remove front bumper assembly → remove air cleaner → remove air cleaner intake duct;
2. Right front group: Disconnect right front headlamp harness connector → right front horn → right front crash sensor → loosen ground point above right front side member → disconnect harness to engine compartment latch → right front horn → windshield washer pump harness;
3. Remove engine compartment fuse box → remove PEB tray;
4. Left front group: Disconnect left front headlamp → loosen ground point above left front side member → left front crash sensor → pedestrian warning speaker → EDU harness connector → cooling fan motor → rear oxygen sensor;
5. Remove brake modulator valve → remove A/C intake grille;
6. Engine/dash panel group: Disconnect connector to engine harness → loosen ground point below engine fuse box → left front wheel speed sensor → electronic water pump-PEB harness connector → brake light signal switch → brake pedal position sensor → vacuum sensor → front wiper motor → loosen ground point below dash panel → disconnect ECM harness connector → HVAC box harness → A/C pressure switch → right front wheel speed sensor;
7. Passenger compartment group: Remove A-pillar lower trim → center console heater blower cover → driver side instrument panel lower cover → disconnect BCM harness connector → disconnect connector to body harness → loosen ground point below BCM → passenger compartment fuse box harness → instrument panel harness → pedestrian warning module harness → ground point on dash panel → remove accelerator pedal → remove brake pedal → disconnect EPS harness → electric heater harness;
8. Release harness retaining clips and remove engine compartment harness.

Installation reverse order (51 steps): Route harness and secure with clips → restore connectors one by one → tighten all ground points one by one → reinstall pedals/trim/PEB tray/fuse box → install manual service disconnect → connect negative terminal.

Key point: Ground points are paired as "loosen→tighten"—there are 6 ground points: right front side member, left front side member, below engine fuse box, below dash panel, below BCM, and on dash panel. Missing any one will cause new electrical faults.

Electric Drive Transmission (EDU) Harness

Removal (following the high-voltage discipline above, after waiting 5 minutes): Remove underbody deflector → disconnect engine electronic water pump connector → remove PEB tray → disconnect oil pump connector → disconnect valve body harness connector → disconnect two high-voltage interlock connectors → disconnect EDU harness-to-engine compartment harness connector → disconnect output shaft speed sensor connector → remove 1 bolt securing EDU harness ground wire to EDU housing → disconnect electronic vacuum pump harness → disconnect parking mechanism connector → release harness clips and remove EDU harness.

Installation: Secure with clips → parking mechanism connector → vacuum pump → tighten ground wire 1 bolt → speed sensor → engine compartment harness connector → two high-voltage interlock connectors → valve body harness → oil pump connector → PEB tray → engine electronic water pump → underbody deflector.

Other Harness Quick Reference

• Instrument panel harness: Disconnect negative terminal → remove manual service disconnect → remove instrument panel related trim → disconnect connectors → remove; install in reverse order;
• Tailgate harness: Luggage side trim assembly → luggage compartment lid inner liner assembly → connectors → remove; install in reverse order → connect negative terminal;
• 12V power outlet: Disconnect negative terminal → pry open shift panel assembly clips → center console front storage box clips → disconnect USB and 12V power outlet connectors → remove outlet from storage box. Installation: insert cigarette lighter socket from front and secure with clips → install storage box and connect connectors → clips → shift panel clips → connect negative terminal.

Safety Warnings

• This article is for technical reference. Work on the high-voltage system (around the EDU harness) must be performed by personnel trained on this vehicle's high-voltage system; low-voltage harness replacement should be performed by professional technicians per OEM specifications.
• Dual power-off + 5-minute wait are both essential (high-voltage capacitor discharge time); check insulated gloves for leaks each time; prevent fluid splashing onto high-voltage components.
• Keep the negative cable and manual service disconnect open until installation is complete; only restore after all connectors are mated.
• Tighten all 6 ground points one by one; secure harness routing with clips to avoid interference with moving parts or heat sources.

Repair Insights

The harness replacement manual is often treated as "pure physical labor," but these 51 steps hide two key disciplines: "ground points in pairs"—for every ground point removed, you must tighten it at the corresponding installation step; intermittent faults caused by missing ground points (lights flickering, sensor drift, occasional CAN interruptions) are harder to diagnose than the original fault; "high-voltage discipline applies to peripheral harnesses"—the EDU harness is only low-voltage wiring, but it sits next to high-voltage interlock connectors, and the manual still requires training threshold + dual power-off + 5-minute wait, because the moment of plugging/unplugging interlock connectors is a high-voltage system state change. Two common high-frequency error points: Don't start work immediately after ignition off—the PEB high-voltage capacitors need 5 minutes to discharge; verify no voltage with a meter before touching anything; keep the negative terminal and MSD open during installation—this is not conservative; it's protection against "system self-powering mid-installation." Finally, the fluid discipline: brake fluid, washer fluid, or coolant splashing onto high-voltage parts can reduce insulation or cause short circuits—seal nearby pipe openings before replacing harnesses.

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【This article is for reference only】