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Functional & Technical Overview
Yazaki Pune — Product Categories at a Glance
A reference module covering Wiring Harness (WH), Electronics & Instrumentation (EI), and CDDC-LV / HV components — what they do, how they vary by customer, the engineering and warranty challenges they face, the design-approval steps for variants, and the typical manufacturing process flow.
WH
~30%
Wiring Harness (LV / HV) — the vehicle’s electrical nervous system. Routes power and signals between sources, controllers, sensors, and loads.
EI
~45%
Electronics & Instrumentation — AR HUD, instrument clusters, sensors, driver-monitoring and HMI electronics. The “brains and dashboard” of the cabin experience.
CDDC
~25%
CDDC-LV / HV components — connectors, terminals, fuse / junction / relay boxes, grommets, protectors, BMS, PDU, BFT and HV components. The “joints, switches and gatekeepers” of the harness ecosystem.
How to use this module
Each product category below is broken into five collapsible sections — Function, Customer variation, Technical & warranty challenges, Design & approval steps, and Manufacturing process. A 10-question knowledge check at the end consolidates the key concepts. Click any section header to expand or collapse it.
1. Wiring Harness (WH) — LV & HV
~30% of mix
Core Yazaki product since 1941
12 V LV & 400–800 V HV
1.1 Functions of a Wiring Harness
A wiring harness is a pre-assembled, branched bundle of insulated conductors, terminals, connectors, grommets, protective tape, conduits and clips that delivers power, ground return, signals and data across the vehicle in a single, fitted assembly. It is the vehicle’s nervous system.
Primary functions
- Power distribution (LV): route 12 V / 24 V / 48 V battery power from the source through fuses to lights, motors, ECUs, infotainment, switches.
- Power distribution (HV): route 400–800 V DC from the traction battery to the inverter, motor, on-board charger and DC-DC converter, with EMI shielding and HV-safety interlocks.
- Signal transmission: carry analog sensor signals (temperature, position, current) and digital network traffic (CAN, LIN, FlexRay, automotive Ethernet) between ECUs.
- Ground return path: provide low-resistance return to chassis / battery negative for every active circuit.
- Mechanical packaging: hold conductors in fixed routes through tight engine bays, doors, dashboards and underbody zones without chafing, pinching, or interfering with moving parts.
- Protection: insulate against abrasion, vibration, heat, fluids (oil, coolant, salt spray), moisture and EMI.
- Service interface: provide standardised mating points (connectors) so that ECUs, sensors and sub-systems can be replaced in the field without re-wiring.
Typical harness families in a modern car
| Harness | Where it runs | Notable loads / nets |
|---|---|---|
| Engine / E-motor harness | Engine bay or e-axle | Injectors, sensors, alternator / inverter, starter |
| Main / dashboard harness | Behind IP, A-pillar to A-pillar | Cluster, HUD, HVAC, infotainment, BCM, fuse box |
| Body / floor harness | Under carpet, sill to sill | Seats, airbags, door triggers, lighting |
| Door harness | Through grommet into door | Window motor, mirror, speakers, lock, switches |
| Roof harness | Headliner | Map lamps, sunroof, antenna, microphones, e-call |
| Rear / tailgate | Boot floor & gate | Tail lamps, parking sensors, camera, defogger |
| HV harness (EV/HEV) | Battery → inverter → motor; OBC → charge port | Traction power, fast-charge, e-compressor, PTC heater |
1.2 How functions vary from customer to customer
Every OEM (Tata, Mahindra, M&M, MG, Renault-Nissan, Stellantis, Toyota, etc.) writes the harness against its own platform architecture and Customer-Specific Requirements (CSRs). Even when the function is “the same”, the realisation is rarely interchangeable.
| Dimension | How it can differ between OEMs |
|---|---|
| Electrical architecture | Distributed ECUs vs. domain controllers vs. zonal (zone-ECU) — changes harness topology and trunk length. |
| Network protocols | CAN-FD, FlexRay, LIN, automotive Ethernet (100/1000Base-T1), shielded twisted pair, optical — mix and ratio differs per OEM. |
| Voltage class | 12 V only (ICE), dual 12 V + 48 V mild-hybrid, full HV 400 V / 800 V EV. |
| Connector standards | Each OEM specifies approved connector families (USCAR, JASO, customer-proprietary) and terminal types. |
| Wire material | Copper, copper-alloy, aluminium for weight saving; cross-sections from 0.13 sq mm to 95 sq mm+. |
| Insulation grade | PVC, XLPE, ETFE, silicone — driven by temperature zone (T2 +85 °C → T5 +175 °C) and chemical exposure. |
| Protection style | PVC tape, fleece tape (cabin acoustic), corrugated tube, woven sleeve, heat-shrink — per OEM “wrap matrix”. |
| Length & weight target | Premium OEMs push for lightest harness (Al wires, 0.13 sq); cost-focused programmes prioritise cheapest BOM. |
| Label / marking | Customer-specific labelling, 2D barcodes, traceability rules (PPAP Level 3, IMDS). |
| Variant complexity | One OEM may have 50 trim variants per model; another runs 4. Drives modular vs. monolithic harness design. |
| Validation matrix | Different OEM-specific test specs (e.g. Renault 32-00-001, Toyota TSC, Mahindra MES) layered on top of LV 214 / ISO 6722 / USCAR-2. |
Practical implication
A harness for a Mahindra BE 6 and a harness for a Tata ICE sedan share almost no common part numbers even though both “deliver power and signals”. Tooling, layout boards, test programs and packaging are platform-specific.
1.3 Technical & warranty challenges
Short-term (during production / launch)
- Crimp quality variation: crimp height, pull-force and cross-section must stay within Cpk targets. Most production rejects originate here.
- Cavity loading errors: a single terminal in a wrong connector cavity causes electrical test failures or worse, undetected mis-wires.
- Seal & grommet insertion: missing or mis-seated seals lead to leak rejects.
- Layout board fidelity: branch length / break-out angle errors cause fit-in-vehicle issues at the OEM line.
- Engineering churn: late ECN (Engineering Change Notice) from the OEM forces in-flight changes to BOM, board, and test program.
- Material availability: connector or specialty wire shortages disrupt JIT supply.
- Operator skill: harness is labour-intensive; new operators have a learning curve before First-Time-Right reaches target.
Long-term (vehicle in use, 8–15 year service life)
- Vibration fatigue: repeated flex breaks conductor strands, especially at branch breakouts and connector entries.
- Fretting corrosion: micro-motion at terminal contacts (driven by thermal cycling) raises contact resistance over time.
- Chafing & abrasion: contact with sharp body panels or moving parts wears through insulation, causing shorts.
- Moisture ingress: failed seals → corrosion of copper → open circuits or intermittent faults.
- UV / heat ageing: insulation embrittlement, especially under-bonnet and on underbody runs.
- Connector unlatching: partial-mate connectors loosen under vibration, leading to intermittent / no-fault-found warranty cases — among the costliest defects to diagnose.
- Rodent damage (field reality, not a design defect, but a frequent warranty conversation).
Industry data point
Wiring harness defects have been cited as the cause of the large majority of automotive electrical recalls. In 2021, wiring harness defects accounted for 84% of automotive electrical recalls in China alone, affecting 8.73 million vehicles. Even small defect rates translate to large warranty exposure at OEM volumes.
1.4 Typical design & approval steps for a variant
For any harness — whether a brand-new platform or a variant of an existing one — a Tier-1 like Yazaki follows the APQP (Advanced Product Quality Planning) framework under IATF 16949, culminating in a PPAP (Production Part Approval Process) submission to the OEM.
- RFQ & concept study: OEM shares vehicle architecture, load list, routing CAD; Yazaki responds with feasibility, weight/cost estimate, and timing plan.
- Electrical design: circuit diagram (E/E schematic) is built from the OEM load list — wire colour, cross-section, fuse rating, splice positions, ground points.
- Physical / 3-D routing: using CATIA / NX with packages like CHS, Capital Harness or VeSys, the harness is routed in 3-D against vehicle CAD; clip and grommet positions are fixed.
- BOM & KSK / module split: the harness is divided into manufacturable sub-modules (KSK = Kunden Spezifischer Kabelbaum / customer-specific harness).
- DFMEA: Design Failure Mode & Effects Analysis — vibration, chafe, EMI, thermal, mis-mating risks are scored and mitigated.
- 2-D flattening & formboard drawing: the 3-D harness is flattened into a layout-board drawing with all branch lengths.
- Prototype build & vehicle trial: hand-built samples for the OEM’s engineering prototype build (mule, alpha, beta).
- DV (Design Validation): environmental, electrical, mechanical tests per ISO / OEM specs.
- PFMEA & control plan: Process FMEA, control plan, work instructions, error-proofing.
- Tooling & jig design: formboard, applicators, EOL test stand programming.
- PV (Production Validation): off-tool production samples; full test matrix.
- PPAP submission: Level 3 typically — drawings, IMDS, capability studies, crimp cross-sections, hi-pot reports, etc.
- SOP (Start of Production): ramp-up curve, safe-launch quality gates.
- Variant management: for each new variant, an engineering-change run-through (steps 2–12 in reduced form) is repeated.
Note on PPAP
A standard Level 3 PPAP for a wire harness includes 18 elements, such as dimensional layouts, material certifications, and Statistical Process Control charts demonstrating a high Cpk/Ppk capability for critical terminal crimps. A manufacturer cannot ship production volumes without an approved PPAP warrant.
1.5 Manufacturing process flow
Wiring harness is labour-intensive and quality-gate intensive. The flow below is the typical sequence at a Yazaki-style plant. Yellow blocks are dedicated quality / inspection gates; the navy block is dispatch.
WH — Manufacturing Process Flow
01 QCIncoming Material Inspection
→
02Wire Cutting (auto cut-strip)
→
03Stripping & Marking
→
04Terminal Crimping
↓
07Sub-assembly (splices, sleeves)
←
06Twisting & Shielding (CAN / Eth)
←
05 QCCrimp Cross-section & Pull-force
↓
08Connector / Cavity Loading
→
09Formboard Assembly (layout)
→
10Taping / Tubing / Clipping
↓
11 QCEOL Continuity Test (100%)
→
12 QCHi-Pot / Insulation (HV)
→
13 QCVisual / Dimensional
→
14Labelling & Packaging
→
15JIT Dispatch to OEM
Key controls at each stage
| Stage | Critical control |
|---|---|
| Cutting | Length tolerance (±2 mm typical); spool-end / batch traceability. |
| Crimping | Crimp Force Monitoring (CFM) on every cycle; periodic cross-section / pull-force test. |
| Twisting | Lay length, shield continuity for data nets. |
| Cavity loading | Poka-yoke fixtures; image-vision check for correct terminal & orientation. |
| Formboard | Branch length to drawing, clip positions, taping wrap-ratio. |
| EOL test | 100% continuity + short-to-short + diode/component check. |
| Hi-Pot | For HV harnesses, dielectric withstand at typically 2× rated voltage. |
| Packaging | Anti-damage cradles, route-specific bags, label / barcode for JIS sequencing. |
2. Electronics & Instrumentation (EI) — AR HUD, Sensors, HMI
~45% of mix
Highest-growth, highest-tech category
AR HUD shipped on Mahindra BE 6 / XEV 9e
2.1 Functions of EI products
EI products are the user-facing and perception-facing intelligence of the vehicle. They sense the world, present information to the driver, and increasingly merge the two via Augmented Reality.
Major EI sub-categories
| Sub-category | Primary function |
|---|---|
| AR HUD | Project navigation, ADAS, speed and warning graphics into the driver’s forward field of view, overlaid on the real-world road scene. |
| Conventional HUD (W-HUD / C-HUD) | Project basic info (speed, turn-by-turn) on windshield or combiner glass. |
| Instrument cluster | Display vehicle state (speed, fuel/SoC, gear, warnings) — analogue, hybrid or full TFT. |
| Driver Monitoring System (DMS) | Camera + processor to detect drowsiness, distraction, gaze. |
| Sensors (Yazaki domain) | Fuel-level senders, current sensors, oil temperature sensors, contactless senders. |
| HMI integrated control units | Combine cluster, HUD and infotainment control in a single ECU. |
| Charging inlets with illumination | EV charge port assembly with status lighting. |
What an AR HUD actually does — the function chain
- Receives data over CAN / Ethernet — speed, navigation, ADAS objects, lane info.
- A Picture Generation Unit (PGU — DLP, LCoS or laser-based) creates the source image.
- Optics (mirrors, freeform aspheric, fold mirror) project the image onto the windshield.
- The windshield acts as a combiner — the driver sees a virtual image at a far virtual distance (typically 7–15 m for AR-HUD vs. 2–3 m for W-HUD).
- The image is rendered in spatial registration with the real road: arrows curve along the lane, hazard markers stick to objects.
Why AR over conventional HUD
AR HUDs can display information in the context of the current driving situation, merging the information with the real-world environment — for example, navigation instructions can be overlaid onto the road ahead, highlighting the correct turns or exits in the field of view of the driver.
2.2 How EI functions vary from customer to customer
| Variation axis | Range across OEMs |
|---|---|
| HUD type | Combiner HUD (small plastic glass) → Windshield HUD → AR-HUD (large virtual image, eye-box matched to driver). |
| Field of View (FoV) | Small (~5°×1°) for basic HUD → large (10°×4°+) for AR. |
| Virtual image distance (VID) | 2 m (W-HUD) to 15 m+ (AR-HUD). |
| PGU technology | TFT-LCD, DLP, LCoS, MEMS laser scanning — each with brightness / contrast / cost trade-off. |
| Brightness target | Indian sun-load is higher than European; OEMs in tropical markets demand higher nits. |
| Compute architecture | Dedicated HUD ECU vs. rendered by a central HMI / cockpit SoC. Defines what Yazaki supplies — hardware only, hardware + firmware, or full hardware + software + UX. |
| UX / graphics | Each OEM brands its HUD graphics — typeface, colour, motion, ADAS cues — uniquely. |
| Cluster type | Analogue + LCD insert (entry) → full TFT 12.3″ (mid) → curved & multi-screen (premium). |
| Sensors | Fuel sender resolution, type (rheostat vs. contactless); current-sensor accuracy class. |
| Functional safety class | ASIL-A to ASIL-B for cluster / HUD warnings; defines redundancy and diagnostic coverage. |
| Software lifecycle | FOTA (firmware over-the-air) updateable HUD vs. fixed firmware. |
Real-world example
The AR HUD that Yazaki India supplies for the Mahindra BE 6 / XEV 9e (“Vision X”) is tuned to Indian glare, Indian roads, Mahindra’s UX brand — a different SKU from any other OEM AR HUD even if the optical engine is reused.
2.3 Technical & warranty challenges
Short-term (production / launch)
- Optical alignment: AR-HUD requires sub-arc-minute mirror alignment over the eye-box — every unit must be calibrated and EOL-tested for distortion, ghost, double-image.
- Windshield tolerance pairing: windshield curvature varies; HUD must either compensate digitally or be paired/coded to the vehicle.
- SMT / PCB yield: high-density boards with FPGAs / SoCs require strict reflow process control and X-ray BGA inspection.
- EMI / EMC: high-current EV environment + sensitive imaging electronics → shielding and ground design is hard.
- Software integration: harmonising HUD graphics with navigation, ADAS and cluster on the OEM’s network is iterative and time-pressured.
- Component obsolescence: semiconductors with 18–36 month lifecycles vs. 5–7 year vehicle programmes force LTBs (Last Time Buys) and re-qualifications.
Long-term (in-use)
- LED / laser source degradation: brightness drop-off over 10–15 years; must be specified with adequate headroom.
- LCD / TFT clouding, dead pixels: thermal cycling on top of dash exposes display to extremes.
- Capacitor & solder-joint fatigue: classic root cause of intermittent cluster / HUD faults.
- Thermal stress: dashboard temperatures in parked vehicles reach 85 °C+ in India; HUD optics and electronics must survive.
- UV degradation of optical films and adhesives in the optical path.
- Calibration drift: AR registration accuracy can drift; vehicles may need re-calibration after windshield replacement.
- Software defect tail: graphics glitches, freezes, “no-fault-found” warranty cases — these are often the largest cost in EI long-term.
2.4 Typical design & approval steps for an EI variant
EI design is a mechatronics + software activity, layered on top of the same APQP / PPAP rhythm. ISO 26262 (functional safety) and Automotive SPICE (software process) typically apply.
- Customer requirement capture: OEM provides Statement of Work (SOR), HMI styleguide, ADAS interface, mechanical package, ASIL target.
- System architecture: partition into PGU, optics, electronics, software, harness interface; allocate ASIL decomposition.
- Optical design: ray-trace simulation, eye-box mapping, sun-load and back-reflection analysis (CodeV / Zemax / LightTools).
- Mechanical & thermal design: housing, mirror mounts, motorised mirror (for adjustable virtual image), thermal simulation.
- Electrical design: schematic, PCB layout, power tree, EMC pre-compliance.
- Software design: Autosar-Classic / Autosar-Adaptive stack, graphics framework, FuSa software unit per ISO 26262.
- DFMEA + safety analysis: FTA, FMEDA for ASIL parts.
- Alpha / Beta prototypes: vehicle integration, customer evaluation drives.
- DV testing: optical (luminance, contrast, ghosting), environmental (thermal shock, salt spray, vibration), EMC, ESD, functional safety.
- Tooling & SMT line setup: stencil, pick-and-place programs, AOI / X-ray, EOL test rig with collimator & camera for AR-HUD optical EOL.
- PV build & capability study.
- PPAP + software release (per ASPICE): dossier including IMDS, FuSa case, software release notes.
- SOP & safe-launch: tighter EOL gates and field-monitoring during the first months.
- Variant management: windshield variants, RHD/LHD, market-specific graphics, SW patches — each managed as a controlled change.
2.5 Manufacturing process flow (AR HUD / Cluster)
EI — Manufacturing Process Flow (representative — AR HUD)
01 QCIncoming Inspection (PCB, optics, housing)
→
02SMT Line (paste, place, reflow)
→
03 QCAOI + X-Ray (BGA)
→
04Through-hole / Press-fit
↓
07Optical Sub-assembly (mirrors, PGU)
←
06Software Flashing & ICT
←
05 QCPCBA Functional Test
↓
08Final Assembly (housing + optics + PCBA)
→
09 QCOptical Calibration & EOL (image, distortion, luminance)
→
10 QCRun-in / Burn-in (thermal)
↓
11 QCFinal Visual / Cosmetic
→
12Serialisation & Labelling
→
13Packaging (ESD-safe)
→
14Dispatch to OEM
Key difference from WH manufacturing
EI lines are cleanroom-grade, low-volume, high-mix, high-capex. WH lines are labour-grade, high-volume, configurable. Yield economics, capacity planning and quality systems differ fundamentally even within the same plant.
3. CDDC — Connectors, Terminals, Boxes & HV Components
~25% of mix
Sold as components & consumed internally in WH
Spans LV connectors to 800 V HV interlocked systems
3.1 Functions of CDDC products
CDDC components are the discrete electromechanical building blocks that, with wire, make up a harness — plus the protection and distribution boxes that consolidate circuits, plus the high-voltage units that govern EV power flow.
| Component family | Function |
|---|---|
| Connectors | Mate / unmate two wires or a wire to a device; provide retention, polarisation, environmental sealing and (for HV) safety interlock. |
| Terminals | The metallic contact crimped onto the wire end; deliver low-resistance, gas-tight electrical contact to the mating terminal. |
| Fuse boxes / Junction boxes | Centralise power distribution, fuse / relay protection and circuit splitting. |
| Relay boxes | Switch high-current loads (motors, lights) using low-current control signals. |
| Grommets | Seal the harness passage through body panels (firewall, door); prevent water and dust ingress. |
| Protectors | Moulded plastic shells that guide and protect harness branches at routing-critical points. |
| BMS (Battery Management System) | Monitors cell voltage, temperature, current; balances cells; manages contactors and safety states. |
| PDU (Power Distribution Unit) | HV switching, fusing and distribution from the battery pack to inverter, OBC, DC-DC, e-compressor. |
| BFT (Battery Front Terminal) / battery posts | Heavy-current termination on the battery — typically forged or cast. |
| HV connectors & service plugs | Disconnect HV circuits safely for service; provide HVIL (interlock) signalling. |
What HV connectors specifically have to do
- Carry tens to hundreds of amps at 400–800 V continuously.
- Survive short-circuit fault current until upstream protection clears.
- Provide EMI shielding (360° shield termination) — critical for inverter / motor noise.
- Provide HVIL (High-Voltage Interlock) — a low-current loop that signals “connector mated” to the BMS.
- Provide “last-mate / first-break” sequencing so HV power is never live during mate / unmate.
- Withstand thermal cycling, vibration, and (for charge inlets) thousands of mating cycles.
Yazaki’s heritage in HV
Yazaki has been a leader in high-voltage connection system development since 1990, drawing on extensive experience in wire harnesses, connectors and battery posts/terminals. Yazaki technologies include EMI shielded connection systems, “last-mate/first-break” safety features, high voltage/low current systems, and conductive and inductive charging systems.
3.2 How CDDC functions vary from customer to customer
| Variation axis | Range |
|---|---|
| Connector “family” | Each OEM has approved families (USCAR, JASO, MQS/AMP, MCON, YESC etc.); cross-acceptance is limited. |
| Sealing class | Unsealed (IP00) for cabin → IP67 / IP6K9K for under-bonnet / underbody. |
| Current / voltage rating | 0.5 A signal connectors → 400 A HV power connectors at 800 V. |
| Plating | Tin for LV cost-driven; silver / gold for HV / data / low-level signals. |
| HVIL implementation | Shorting pin, dedicated 2-pin loop, optical loop — OEM choice. |
| Fuse-box architecture | Centralised single-fusebox vs. distributed mini-boxes vs. e-fuse (semiconductor fusing). |
| BMS architecture | Centralised, distributed (slave + master), wireless BMS — OEM-driven, cell chemistry-driven (LFP vs. NMC vs. solid-state). |
| PDU integration level | Standalone PDU vs. integrated with OBC + DC-DC in a “3-in-1” or “Power Electronics Box”. |
| Charge inlet standard | CCS2 (India / EU), CCS1 (NA), CHAdeMO (legacy JP), GB/T (China), NACS / J3400 (NA emerging) — different mechanicals, signalling, current ratings. |
| Diagnostic data | OEMs differ on which BMS signals are reported, at what rate, and over which network. |
3.3 Technical & warranty challenges
Short-term (production)
- Injection moulding consistency: shrinkage, short-shots, sink marks in connector housings; require tight tool control.
- Terminal plating uniformity: tin / silver / gold thickness within spec across the reel.
- Stamping burr & spring force: female terminal spring force directly drives contact resistance.
- Box / PDU assembly: bus-bar tightening torque, leak test (for sealed boxes), HV insulation withstand.
- HV PDU functional test: contactor make/break, pre-charge timing, isolation resistance — every unit, every time.
- BMS PCB calibration: cell-voltage sense channels must be calibrated within mV; current sensor zero-offset trimmed.
Long-term (in-use)
- Fretting corrosion at terminal contacts from thermal cycling and micro-vibration.Fretting wear occurs under small-amplitude oscillations of 1 to 100 μm, often induced by temperature fluctuations and background vibration; thermal expansion differences between materials can generate micro-motions that compromise contact integrity over millions of cycles.
- Seal compression set: rubber seals harden over 10+ years, losing IP rating.
- HV insulation ageing: XLPE / silicone cable insulation degrades with heat and partial discharge.
- Contactor weld / arc wear in PDU: contactors that switch under load wear; degradation must be monitored by BMS.
- BMS sensor drift: shunt-based current sense and voltage references can drift, affecting SoC accuracy.
- EMI gasket / shield ageing: conductive elastomers oxidise, raising shield impedance.
- Field-replacement quality: service technicians can mis-mate connectors, omit seals, damage HVIL pins — generating warranty issues that look like product defects.
Safety-critical for HV
A single HV connector failure (loss of shielding, partial mate, melted contact) can create thermal runaway risk, EMI failures, or hazardous voltage exposure. This is why HV CDDC products are typically designed to a higher safety target (ASIL-C / ASIL-D involvement for BMS and PDU) than LV components.
3.4 Typical design & approval steps for a variant
For most CDDC components there are two flavours of design effort:
- Catalogue product (e.g. a standard YESC sealed connector) — already tested to USCAR / JASO; variant work is mostly cavity / colour / keying changes plus customer-specific labelling and PPAP.
- Application-specific product (e.g. a PDU, a BMS slave board, a customer-unique HV connector) — full new-development flow.
Full design & approval flow
- Voice of customer: current, voltage, temperature class, mating cycles, packaging space, target cost.
- Concept selection: off-the-shelf vs. variant vs. new platform; cost / risk trade-off.
- Mechanical design: housing, terminal, seal, latch, polarisation — 3-D CAD + mould-flow / tolerance stacks.
- Electrical design (for PDU / BMS / fuse-box): schematic, bus-bar design, derating analysis, fault-current calculation.
- Thermal design: FEA / CFD for high-current parts; conductor heat-rise simulation.
- DFMEA + DV plan: per USCAR-2 / -25 / -38 for connectors; ISO 6469 for HV; LV 124 for electronics.
- Prototype tool (soft tool): rapid steel inserts, short-run mouldings for DV samples.
- Design Validation: mechanical (insertion / withdrawal force, terminal retention, vibration, drop), environmental (thermal shock, salt spray, immersion), electrical (current cycling, voltage drop, dielectric withstand, HVIL function).
- Production tool release: hardened steel tools, automated assembly cells.
- PV samples + capability study.
- PPAP submission.
- SOP, run-at-rate, safe-launch.
- Variant management: for each customer-specific colour, cavity arrangement or label, a sub-PPAP / “delta” approval is run.
3.5 Manufacturing process flow
(a) Connectors & terminals (component-level)
CDDC — Connector / Terminal Manufacturing
01 QCResin / Strip Incoming
→
02Stamping (terminal)
→
03Plating (Sn / Ag / Au)
→
04 QCPlating Thickness / Visual
↓
07Sub-assembly (seal / lever / TPA)
←
06 QCMould Dimensional Check
←
05Injection Moulding (housing)
↓
08 QCMating Force / Function Test
→
09Packaging (reel / tray)
→
10Dispatch (to WH plant / OEM)
(b) Junction box / PDU / BMS (assembly-level)
CDDC — JB / PDU / BMS Assembly
01 QCIncoming PCBA / Bus-bar / Housing
→
02Bus-bar Assembly & Torque-down
→
03PCBA Mount + Fuses / Relays / Contactors
↓
06Software Flash & Calibration (BMS / PDU)
←
05 QCHi-Pot / Insulation Resistance
←
04Cover / Seal Assembly
↓
07 QCFunctional Test (contactor, current, comm.)
→
08 QCLeak Test (sealed)
→
09Serialise & Package
→
10Dispatch
100% test on HV product
For BMS, PDU, HV junction boxes and HV connectors, every single unit goes through Hi-Pot / IR / functional test — there is no sampling, because a single field failure can be a safety event.
Knowledge Check
10 questions covering the three product categories. Click an answer to see the feedback. Your running score appears at the bottom.
Q1. The wiring harness category (WH) is approximately what share of the example product mix discussed in this module?
A. ~15%
B. ~30%
C. ~45%
D. ~60%
Correct — WH ≈ 30%, EI ≈ 45%, CDDC ≈ 25%.
Q2. Which is NOT a primary function of an automotive wiring harness?
A. Power distribution
B. Signal & data transmission
C. Generating regulated DC supply
D. Ground return path
Correct — generating regulated DC supply is the job of a DC-DC converter, not the harness. The harness only routes power.
Q3. The “last-mate / first-break” feature on an HV connector exists primarily to:
A. Reduce mating force for the technician
B. Ensure the HV circuit is never live during mate / unmate
C. Improve EMI shielding
D. Allow underwater operation
Correct — it is an HVIL-related safety feature ensuring power is opened before contacts separate.
Q4. Which production-stage defect is the single biggest contributor to harness rejects?
A. Tape colour mismatch
B. Wire spool changeover
C. Label printing errors
D. Crimp quality variation (height, pull-force)
Correct — crimp variation is the most common manufacturing reject source and the focus of CFM (Crimp Force Monitoring).
Q5. Compared with a conventional Windshield HUD, an AR HUD typically has a:
A. Larger field of view and farther virtual image distance
B. Smaller field of view but higher pixel density
C. Same FoV but mounted on a combiner glass
D. No optical system — direct projection only
Correct — AR-HUD typically targets 10°×4° FoV with virtual image distance of 7–15 m so graphics can be registered with the real road.
Q6. Which long-term failure mode is most associated with thermal-cycling-induced micro-motion at a terminal contact?
A. Conductor work-hardening
B. UV embrittlement
C. Fretting corrosion
D. Tin whiskering
Correct — fretting wear from micro-motion (1–100 μm) is a classic long-term cause of rising contact resistance.
Q7. Under IATF 16949, the formal customer-approval dossier required before serial shipment of a new harness is called the:
A. DFMEA
B. PPAP
C. CSR
D. APQP
Correct — PPAP (Production Part Approval Process); APQP is the planning framework, DFMEA is one element, and CSR = Customer Specific Requirements.
Q8. Functions of a Power Distribution Unit (PDU) in an EV include all EXCEPT:
A. HV switching with contactors
B. HV fusing
C. Distributing power to inverter, OBC and DC-DC
D. Generating navigation graphics for the HUD
Correct — HUD graphics are an EI function, not a PDU function.
Q9. Why does CDDC manufacturing of HV products use 100% (not sample) Hi-Pot and functional testing?
A. Any single field failure can be a safety event
B. To keep test equipment busy
C. Because HV products are cheaper than LV
D. To comply with ISO 9001 alone
Correct — HV failure can lead to thermal runaway, shock or shield breach, so every part is screened.
Q10. Which one of the following best explains why variants of “the same” product cannot be reused across two different OEMs without re-design?
A. Indian OEMs use different voltage levels for the same function
B. There is no standardisation in the automotive industry
C. Each OEM imposes its own Customer-Specific Requirements (architecture, connector families, network protocols, validation specs, UX)
D. Tier-1s deliberately differentiate to lock in customers
Correct — OEM CSRs (architecture, approved connectors, validation specs, branding) drive variant-level differentiation even when the underlying function is identical.