• Electrical Manuals: EM30K6E, EM30K5E
• Chassis Code: AVE30L
• Engines: 2AR-FSE

Get the same comprehensive level of information that your Lexus local dealer technicians have in a simple PDF format. It’s simple, and straightforward with only the manufacturer’s authorized service and repair procedures which you can follow and do yourself.

Contents: 2014-2020 Lexus IS 300h Wiring Diagram

Electric Manual: EM30K5E

1. Overall Electrical Wiring Diagram
2. Relay Locations
3. Electrical Wire Routing
4. System Wiring Diagram

Electric Manual: EM30K6E

1. Overall Electrical Wiring Diagram
2. Relay Locations
3. Electrical Wire Routing
4. System Wiring Diagram

Sample Pages

2014–2020 Lexus IS 300h: Comprehensive Guide

Overview

The Lexus IS 300h is a compact luxury sport sedan that combines performance with hybrid efficiency. It represents Lexus’s entry into the hybrid sport sedan segment, offering a sophisticated alternative to traditional gasoline-powered luxury compacts.

Generation: Third generation (XE30)
Production Years: 2013–2020 (2014+ for most markets)
Body Style: 4-door sedan
Market Position: Compact luxury sport sedan with hybrid powertrain

Technical Specifications

Powertrain

• Engine: 2.5L inline-4 (2AR-FSE) Atkinson cycle
• Electric Motor: Permanent magnet synchronous motor
• Combined System Output: 220 horsepower
• Transmission: Electronic CVT (eCVT)
• Drivetrain: Rear-wheel drive (RWD)
• 0-60 mph: ~8.3 seconds
• Top Speed: 124 mph (electronically limited)

Fuel Economy

• Combined: 40-42 mpg (depending on market/year)
• City: 42-45 mpg
• Highway: 38-40 mpg

Dimensions

• Length: 183.7 inches
• Width: 71.3 inches
• Height: 56.3 inches
• Wheelbase: 110.2 inches
• Curb Weight: ~3,700 lbs

Suspension & Brakes

• Front Suspension: Double wishbone
• Rear Suspension: Multi-link
• Brakes: Ventilated discs (front), solid discs (rear)
• Brake System: Regenerative braking with ECB (Electronically Controlled Brake)

Battery

• Type: Nickel-Metal Hydride (NiMH)
• Voltage: 244.8V
• Location: Trunk area (reduces cargo space)
• Warranty: Typically 8 years/100,000 miles

Top 10 Mechanical & Electrical Issues

1. Hybrid Battery Degradation

Symptoms: Reduced fuel economy, battery warning light, decreased power, frequent engine cycling
Root Cause: Natural cell degradation over time, especially in high-mileage vehicles (100k+ miles)
Fix: Battery reconditioning or replacement; individual module replacement sometimes possible
Cost: $2,000–$4,500 (full replacement); $500–$1,500 (reconditioning/module replacement)

2. Inverter Coolant Pump Failure

Symptoms: Hybrid system warning, overheating, reduced power, coolant leaks under vehicle
Root Cause: Pump bearing wear, seal failure, or electrical motor failure
Fix: Replace inverter coolant pump assembly
Cost: $800–$1,500 (parts + labor)

3. 12V Auxiliary Battery Failure

Symptoms: Car won’t start, electrical system errors, “Check Hybrid System” message
Root Cause: Small 12V battery drains quickly if car sits unused; shorter lifespan than conventional batteries
Fix: Replace 12V battery (typically every 3-5 years)
Cost: $200–$400

4. Carbon Buildup on Intake Valves

Symptoms: Rough idle, hesitation, misfires, reduced fuel economy, loss of power
Root Cause: Direct injection engines don’t clean valves with fuel; EGR and PCV blow-by cause deposits
Fix: Walnut blasting or chemical cleaning of intake valves
Cost: $400–$800

5. Electric Water Pump Failure

Symptoms: Overheating, coolant leaks, warning lights, steam from engine bay
Root Cause: Pump motor or impeller failure, seal degradation
Fix: Replace electric water pump
Cost: $500–$1,000

6. Dashboard Rattle/Squeaks

Symptoms: Annoying rattles from dashboard, center console, or door panels
Root Cause: Loose clips, poor panel fitment, material expansion/contraction
Fix: Identify source and apply felt tape, tighten clips, or replace clips
Cost: $0–$300 (DIY to dealer fix)

7. Navigation/Infotainment System Freezing

Symptoms: Touchscreen unresponsive, system crashes, slow response, blank screen
Root Cause: Software bugs, outdated firmware, failing head unit
Fix: Software update/reset; head unit replacement if hardware failed
Cost: $0–$200 (update); $1,500–$2,500 (replacement)

8. Transmission Position Sensor Issues

Symptoms: Gear position display incorrect, car won’t shift, warning lights
Root Cause: Sensor wear or electrical connection corrosion
Fix: Replace transmission range sensor
Cost: $300–$600

9. Brake Actuator Noise (Hybrid Brake System)

Symptoms: Whirring, buzzing, or grinding noise when braking at low speeds
Root Cause: Normal operation of regenerative brake actuator; sometimes excessive wear
Fix: Usually normal; replacement if truly defective
Cost: $0 (normal); $2,000–$3,500 (actuator replacement if faulty)

10. Air Conditioning Compressor Failure

Symptoms: No cold air, unusual noises from compressor, intermittent cooling
Root Cause: Compressor clutch failure, refrigerant leaks, internal compressor damage
Fix: Replace A/C compressor, evacuate and recharge system
Cost: $1,200–$2,000

Top 5 Competitors

1. BMW 330e / 320d (Efficient Dynamics)

• More sporty driving dynamics
• Stronger performance
• Higher maintenance costs
• Plug-in hybrid option (330e)

2. Audi A4 2.0 TFSI ultra

• Quattro AWD available
• More advanced technology
• Better interior materials
• Higher running costs

3. Mercedes-Benz C 300 / C 350e

• More luxurious interior
• Stronger brand prestige
• Plug-in hybrid option (C 350e)
• Less reliable than Lexus

4. Infiniti Q50 Hybrid

• More powerful (364 hp combined)
• Sport-oriented chassis
• Lower resale value
• Less fuel efficient

5. Acura TLX (non-hybrid comparison)

• Similar reliability
• Lower price point
• More standard features
• No hybrid option (but competitive efficiency with V6)

Top 10 Recalls, Advisories & TSB Highlights

Recalls

1. Fuel Pump Recall (2020)

• Low-pressure fuel pump may fail
• Can cause engine stalling
• Affects multiple Toyota/Lexus models

2. Passenger Airbag Inflator Recall (Takata)

• Takata airbag inflators may rupture
• Multiple recall campaigns over several years
• Critical safety issue

3. Fuel Suction Tube Recall (2014-2015 models)

• Fuel suction tube may crack
• Can cause fuel leaks and fire risk
• Tube replacement required

Technical Service Bulletins (TSBs)

4. Dashboard Rattle/Noise TSB

• Interior trim rattles and squeaks
• Revised clips and installation procedures
• Common complaint area

5. Brake Actuator Noise TSB

• Grinding/buzzing noise during regenerative braking
• Software updates and revised actuator in some cases
• Often considered “normal operation”

6. Infotainment System Software Updates

• Touchscreen responsiveness improvements
• Navigation updates
• Bluetooth connectivity fixes

7. Carbon Buildup on Intake Valves

• Service recommendation for cleaning at 60k+ miles
• Preventative maintenance rather than recall
• Common to direct-injection engines

8. Transmission Shudder/Hesitation

• eCVT software calibration updates
• Improved throttle response programming
• Mostly early production vehicles

9. Hybrid System Warning Light (False Alerts)

• Software updates to reduce false warnings
• 12V battery sensitivity improvements
• Sensor calibration updates

10. Climate Control Fan Noise

• Excessive fan noise at high speeds
• Revised blower motor or resistor
• Affected specific production batches

Maintenance Schedule

Every 5,000 Miles / 6 Months

• Engine oil and filter change
• Tire rotation
• Visual inspection of brakes, fluids, hoses

Every 10,000 Miles / 12 Months

• Cabin air filter replacement
• Brake inspection

Every 30,000 Miles

• Engine air filter replacement
• Inspect hybrid battery cooling system
• Inspect inverter coolant level

Every 60,000 Miles

• Replace spark plugs
• Inspect/clean throttle body
• Recommended: Intake valve cleaning (carbon buildup)
• Replace engine coolant (hybrid inverter coolant may differ)
• Inspect drive belts

Every 90,000–100,000 Miles

• Hybrid battery cooling filter replacement
• Inspect/replace hybrid battery if showing degradation
• Replace transmission fluid (eCVT)

As Needed

• 12V auxiliary battery (every 3-5 years)
• Brake fluid flush (every 3 years)
• Brake pad replacement (varies widely due to regenerative braking)
• Wiper blades, bulbs, etc.

Note: Lexus recommends 10,000-mile oil change intervals in some markets, but 5,000 miles is safer for longevity, especially for hybrid systems.

10 FAQs for Buyers

1. Is the IS 300h reliable?

Generally yes. Lexus hybrids have excellent reliability records. Main concerns are hybrid battery longevity after 100k miles and typical maintenance items. The 2.5L engine and hybrid system are proven Toyota technology.

2. What’s the real-world fuel economy?

Expect 38–42 mpg combined in normal driving. City driving favors hybrids more (40-45 mpg), while highway efficiency drops slightly (35-40 mpg) compared to city due to less regenerative braking.

3. How long does the hybrid battery last?

Most hybrid batteries last 150,000–200,000+ miles. Degradation becomes noticeable around 100,000–150,000 miles, but many continue functioning acceptably beyond that with reduced efficiency.

4. Is it expensive to maintain?

Moderate. Lexus service is pricier than Toyota but cheaper than German competitors. Hybrid components (battery, inverter) are expensive if they fail outside warranty. Regular maintenance is straightforward.

5. Can I use regular unleaded fuel?

Premium fuel (91+ octane) is recommended for optimal performance, but regular unleaded is acceptable. You may notice slightly reduced power and efficiency on regular.

6. Is the IS 300h fun to drive?

It’s comfortable and refined but not sporty. The CVT and hybrid system prioritize efficiency over performance. If you want engaging driving dynamics, consider the IS 350 F Sport or competitors like the BMW 330i.

7. What’s the cargo space like?

Limited. The hybrid battery in the trunk reduces cargo capacity significantly compared to the gasoline IS models. Rear seats don’t fold flat, further limiting versatility.

8. Should I buy CPO (Certified Pre-Owned)?

Highly recommended. CPO extends the hybrid battery warranty and provides additional coverage. The thorough inspection can catch potential issues before purchase.

9. What year is best to buy?

2016+ models received updates to the infotainment system and styling refresh. 2017+ is ideal for the best technology and refinements. Avoid the earliest 2014 models if possible.

10. Common deal-breakers?

• Infotainment system is dated (no Apple CarPlay/Android Auto in most models)
• Limited rear cargo space
• CVT feels less engaging than traditional automatics
• Not as sporty as competitors

Final Buyer Recommendations

✅ Buy If:

• Fuel efficiency is a priority – The IS 300h delivers exceptional mpg for a luxury sedan
• You value reliability – Lexus hybrids are among the most dependable luxury vehicles
• You drive mostly in city/suburban areas – Hybrids excel in stop-and-go traffic
• You want lower long-term costs – Less brake wear, lower fuel costs offset higher purchase price
• You prefer a refined, quiet ride – Excellent build quality and comfort

⚠️ Consider Carefully If:

• You want sporty driving dynamics – The IS 300h prioritizes comfort over performance
• You need cargo space – Trunk space is significantly compromised by the battery
• You drive mainly highway miles – Hybrid advantage diminishes at sustained highway speeds
• You want the latest tech – Infotainment is dated; no Apple CarPlay/Android Auto in most years

❌ Avoid If:

• You’re on a tight budget – Hybrid repairs (battery, inverter) can be costly outside warranty
• You want maximum performance – Consider the IS 350 or competitors instead
• You prioritize modern connectivity – The infotainment system lags behind competitors

🎯 Smart Buying Tips:

1. Pursue CPO models for extended hybrid warranty coverage (especially important for 2014-2016 models)
2. Get a pre-purchase inspection focusing on hybrid battery health and inverter coolant system
3. Check maintenance records – Regular oil changes and hybrid system services are crucial
4. Look for 2016+ model years for better technology and refinements
5. Budget for hybrid battery if buying high-mileage (100k+) – Factor in potential $2,000-$4,500 expense
6. Test drive in various conditions – Highway, city, hills to understand hybrid system behavior
7. Verify 12V battery condition – Cheap fix but common issue that can cause expensive diagnostic headaches
8. Consider intake valve cleaning as a negotiation point if buying 60k+ mile examples

Value Proposition

The IS 300h is an excellent choice for buyers who prioritize fuel economy, reliability, and refinement over outright performance. It’s a “sensible” luxury sedan that will reward you with low running costs and exceptional dependability. However, it won’t satisfy driving enthusiasts, and the dated technology may frustrate tech-savvy buyers.

Best for: Commuters seeking luxury and efficiency
Skip if: You want the sportiest compact luxury sedan