What is the 2003-2006 Toyota 4Runner 1GR-FE V6 Head Gasket Failure with External Coolant Leak at Rear of Cylinder Head?

Early 4th-generation 4Runners with the 4.0L 1GR-FE V6 are known for head gasket failures, often presenting as an external coolant leak near the rear of the passenger-side cylinder head. Owners report gradual coolant loss, sweet smell, overheating risk, and misfires if the leak wo… Repairs typically run $1,800-$4,000. Severity: high.

What is the 2003-2009 Toyota 4Runner Fuel Gauge Sending Unit Failure Causing Inaccurate Fuel Level Readings?

A recurring owner complaint on 4th-generation 4Runners is an erratic or inaccurate fuel gauge, often reading empty when fuel remains or failing to move smoothly after fill-ups. The usual cause is wear or contamination in the fuel level sending unit inside the tank, though wiring… Repairs typically run $350-$900. Severity: medium.

What is the 2003-2015 Toyota 4Runner Timing Cover Oil Leak at Bank 1 Cylinder Head/Block/Timing Cover Junction (TSB EG007-07)?

The 1GR-FE develops a slow oil seep/leak at the front of the engine where the Bank 1 (passenger-side) cylinder head, engine block, and timing cover all meet. Toyota acknowledged it in TSB EG007-07 for 2003-2007 4Runners, and the leak persists on later 1GR-FE trucks. A secondary l… Repairs typically run $150-$1,500. Severity: medium.

What is the 2003-2009 Toyota 4Runner Cracked Exhaust Manifolds on 4.7L V8 Causing Ticking Noise and Exhaust Leaks?

The 2UZ-FE V8 in 4th-generation 4Runners is known for exhaust manifold cracking, especially as the vehicle ages and heat cycles accumulate. Owners usually hear a cold-start ticking or tapping from the engine bay that quiets somewhat as the manifolds warm up, and some eventually g… Repairs typically run $700-$2,200. Severity: medium.

What is the 1999-2009 Toyota 4Runner Catalytic Converter Efficiency Below Threshold (P0420 / P0430) — Aging or Manifold-Integrated Cats?

As 4Runners accumulate miles, the catalytic converter loses efficiency and the ECU sets P0420 (Bank 1) and/or P0430 (Bank 2) when the downstream O2 sensor starts to mirror the upstream sensor. On the 4th-gen 1GR-FE, the primary cats are integrated into the exhaust manifolds, whic… Repairs typically run $150-$2,500. Severity: medium.

What is the 2000-2009 Toyota 4Runner Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1 Failure (P0125 / P1130 / P0135) — Heater Circuit / Slow Response?

Later 3rd-gen and 4th-gen 4Runners use a wide-band Air-Fuel Ratio (A/F) sensor as the upstream (Bank 1 Sensor 1) oxygen sensor. With age and heat cycling the sensor's internal heater or element degrades, setting codes such as P0125 (insufficient coolant temp for closed loop / A-F… Repairs typically run $120-$400. Severity: medium.

What is the 2003-2024 Toyota 4Runner Serpentine Belt Tensioner / Idler Pulley Bearing Failure Causing Squeal and Belt Wear?

The accessory-drive belt tensioner and idler pulley bearings (a 6203-size sealed bearing) wear out and get noisy on the 1GR-FE, producing a persistent squeal/squeak/grinding from the front of the engine that is often mistaken for the water pump or a glazed belt. A weak tensioner… Repairs typically run $40-$350. Severity: medium.

What is the 2003-2024 Toyota 4Runner High-Mileage Harsh / Jerky Automatic Shifting from Valve-Body Pressure Issues?

On higher-mileage 4Runner automatics owners report harsh/abrupt shifts, jerky 3-2 downshifts, unstable RPM blips while coasting near 40 mph, and delayed engagement. The most common mechanical cause is valve-body pressure control wear - a sticking pressure-regulator or throttle va… Repairs typically run $150-$1,500. Severity: medium.

What is the 2003-2024 Toyota 4Runner Rear Hatch (Back Glass) Power Window Regulator/Motor Failure Won't Roll Up or Down?

The signature rear tailgate power glass on the 4Runner is a high-failure, high-search item. The window stops rolling up or down, rolls part way and falls back, moves slowly/unevenly, or makes grinding noises. Root causes are a worn rear window regulator/motor sub-assembly, a fail… Repairs typically run $120-$500. Severity: medium.

What is the 2003-2009 Toyota 4Runner Front Wheel Bearing / Hub Assembly Noise (4th Gen) — Humming/Growling That Rises With Speed?

High-mileage 4th-gen 4Runners commonly develop front wheel-bearing wear, producing a humming or roaring noise that grows with vehicle speed and changes as the truck loads/unloads a wheel in turns. Off-road use, water/mud intrusion, and heavy tires accelerate it. Left unaddressed… Repairs typically run $100-$600. Severity: medium.

What is the 1996-2009 Toyota 4Runner Power Steering Pump / System Leak & Whine — Reservoir Screen Clog and Seal Failure?

3rd- and 4th-gen 4Runners commonly develop power-steering whine and reddish ATF leaks with age. A whine is often not the pump itself but old fluid or a clogged filter screen in the bottom of the PS reservoir; leaks frequently originate at the union-bolt gaskets, high-pressure/ret… Repairs typically run $20-$500. Severity: medium.

What is the 2003-2009 Toyota 4Runner Instrument Cluster Gauge Stepper-Motor Failure — Dead/Erratic Speedometer & Tachometer (4th Gen)?

4th-gen 4Runner instrument clusters use small stepper motors to drive each gauge needle, and these motors fail with age — most often the speedometer, sometimes the tach, fuel, or temp gauges. Symptoms range from a needle stuck at a false reading (e.g., speedo frozen at ~40 mph) t… Repairs typically run $40-$400. Severity: medium.

What is the 1996-2009 Toyota 4Runner EVAP System Leak — Charcoal Canister / Vacuum Switching Valve (VSV) Failure (P0440 / P0441 / P0446)?

EVAP faults (P0440 general malfunction, P0441 incorrect purge flow, P0446 vent control circuit) are among the most common check-engine codes on 3rd- and 4th-gen 4Runners. Toyota issued service bulletin EG013-03 covering these codes across 4Runner/Camry/Tacoma. The frequent culpri… Repairs typically run $15-$500. Severity: low.

What is the 2003-2009 Toyota 4Runner Dashboard Cracking and Melting from Heat/UV Exposure?

Many 4th-generation 4Runners develop cracked or sticky/melting dashboards, especially in hot climates. Owners report the dash surface becoming shiny, tacky, and prone to deep cracks around the passenger airbag and instrument panel. Toyota acknowledged similar interior panel mater… Repairs typically run $150-$1,800. Severity: low.

What is the 2003-2024 Toyota 4Runner Air-Mix / Blend Door Servo Actuator Failure (Clicking Behind Dash, No Temperature Control)?

The HVAC air-mix (blend) door servo actuators use plastic internal gears that strip over time. When a gear tooth breaks the servo loses calibration and produces a repetitive clicking/ticking sound behind the glove box or center dash, and the climate system can no longer regulate… Repairs typically run $60-$350. Severity: low.

Toyota · Known Issues

2003 Toyota 4Runner Problems: 22 Issues Every Owner Should Know

2003 model year · NHTSA recalls, manufacturer TSBs, and owner forum reports · Updated July 2026

Share:@au7o.io

According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 2003 Toyota 4Runner has 22 documented known issues, with 6 rated critical. The most serious are ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise ($1,200-$3,000 repair), Brake Booster / Master Cylinder Internal Leak Causing Hard Pedal and Reduced Braking Assist ($1,200-$2,800 repair), 4WD Transfer Case Actuator Seizure from Infrequent Use Preventing 4HI/4LO Engagement ($600-$2,200 repair), X-REAS Suspension Hydraulic Shock Leaks Leading to Harsh Ride and Expensive Replacement ($800-$2,500 repair), 1GR-FE V6 Head Gasket Failure with External Coolant Leak at Rear of Cylinder Head ($1,800-$4,000 repair) and 2UZ-FE 4.7L V8 Timing Belt is an Interference Belt - Failure at Neglected 90k Interval Destroys the Engine ($600-$1,500 repair). Across all issues with published estimates, repair costs range from $15 to $4,000. DIY maintenance guides at .

Frequently Asked Questions

What are the most common Toyota 4Runner problems?

According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 2003 Toyota 4Runner has 22 documented issues. The most frequently reported are: ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise, Brake Booster / Master Cylinder Internal Leak Causing Hard Pedal and Reduced Braking Assist, 4WD Transfer Case Actuator Seizure from Infrequent Use Preventing 4HI/4LO Engagement. Of these, 6 are rated critical and should be addressed promptly.

Is the Toyota 4Runner reliable?

The 2003 Toyota 4Runner has 22 known issues compiled from NHTSA recalls, manufacturer TSBs, and owner forum reports. 6 issues are rated critical: ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise and Brake Booster / Master Cylinder Internal Leak Causing Hard Pedal and Reduced Braking Assist and 4WD Transfer Case Actuator Seizure from Infrequent Use Preventing 4HI/4LO Engagement and X-REAS Suspension Hydraulic Shock Leaks Leading to Harsh Ride and Expensive Replacement and 1GR-FE V6 Head Gasket Failure with External Coolant Leak at Rear of Cylinder Head and 2UZ-FE 4.7L V8 Timing Belt is an Interference Belt - Failure at Neglected 90k Interval Destroys the Engine. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common Toyota 4Runner problems?

Repair costs for known Toyota 4Runner issues range from $0 to $4,000, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise, typically costs $1,200-$3,000 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 2003-2009 Toyota 4Runner ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise?

On 4th-gen 4Runners the integrated ABS actuator/brake master cylinder assembly (with electric pump motor and accumulator) fails internally. The pump motor or accumulator wears out so the pump never reaches pressure and runs continuously; owners get simultaneous ABS, BRAKE, VSC an… Repairs typically run $1,200-$3,000. Severity: high.

All 22 Known Issues

Other Toyota Models

Frequently Asked Questions

What are the most common Toyota 4Runner problems?

Is the Toyota 4Runner reliable?

How much does it cost to fix common Toyota 4Runner problems?

What is the 2003-2009 Toyota 4Runner ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise?

When Issues Typically Appear

2003-2006 Toyota 4Runner: 1GR-FE V6 Head Gasket Failure with External Coolant Leak at Rear of Cylinder Head#

2003-2009 Toyota 4Runner: 2UZ-FE 4.7L V8 Timing Belt is an Interference Belt - Failure at Neglected 90k Interval Destroys the Engine#

2003-2015 Toyota 4Runner: Timing Cover Oil Leak at Bank 1 Cylinder Head/Block/Timing Cover Junction (TSB EG007-07)#

2003-2009 Toyota 4Runner: Cracked Exhaust Manifolds on 4.7L V8 Causing Ticking Noise and Exhaust Leaks#

2003-2024 Toyota 4Runner: Serpentine Belt Tensioner / Idler Pulley Bearing Failure Causing Squeal and Belt Wear#

2003-2009 Toyota 4Runner: ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise#

2003-2009 Toyota 4Runner: Brake Booster / Master Cylinder Internal Leak Causing Hard Pedal and Reduced Braking Assist#

2003-2009 Toyota 4Runner: X-REAS Suspension Hydraulic Shock Leaks Leading to Harsh Ride and Expensive Replacement#

2003-2009 Toyota 4Runner: Front Wheel Bearing / Hub Assembly Noise (4th Gen) — Humming/Growling That Rises With Speed#

2000-2009 Toyota 4Runner: 4WD Transfer Case Actuator Seizure from Infrequent Use Preventing 4HI/4LO Engagement#

1999-2009 Toyota 4Runner: Catalytic Converter Efficiency Below Threshold (P0420 / P0430) — Aging or Manifold-Integrated Cats#

2000-2009 Toyota 4Runner: Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1 Failure (P0125 / P1130 / P0135) — Heater Circuit / Slow Response#

1996-2009 Toyota 4Runner: EVAP System Leak — Charcoal Canister / Vacuum Switching Valve (VSV) Failure (P0440 / P0441 / P0446)#

2003-2024 Toyota 4Runner: Rear Hatch (Back Glass) Power Window Regulator/Motor Failure Won't Roll Up or Down#

2003-2009 Toyota 4Runner: Instrument Cluster Gauge Stepper-Motor Failure — Dead/Erratic Speedometer & Tachometer (4th Gen)#

2003-2024 Toyota 4Runner: Air-Mix / Blend Door Servo Actuator Failure (Clicking Behind Dash, No Temperature Control)#

2003-2009 Toyota 4Runner: Blower Motor Resistor Failure — HVAC Fan Only Works On Highest Speed (4th Gen)#

2003-2009 Toyota 4Runner: Fuel Gauge Sending Unit Failure Causing Inaccurate Fuel Level Readings#

2003-2024 Toyota 4Runner: High-Mileage Harsh / Jerky Automatic Shifting from Valve-Body Pressure Issues#

1996-2009 Toyota 4Runner: Power Steering Pump / System Leak & Whine — Reservoir Screen Clog and Seal Failure#

2003-2009 Toyota 4Runner: Dashboard Cracking and Melting from Heat/UV Exposure#

2003-2024 Toyota 4Runner: Clogged Sunroof/Moonroof Drain Tubes Causing Headliner and Floor Water Leaks#

What is the 2003-2009 Toyota 4Runner Brake Booster / Master Cylinder Internal Leak Causing Hard Pedal and Reduced Braking Assist?

What is the 2000-2009 Toyota 4Runner 4WD Transfer Case Actuator Seizure from Infrequent Use Preventing 4HI/4LO Engagement?

What is the 2003-2009 Toyota 4Runner X-REAS Suspension Hydraulic Shock Leaks Leading to Harsh Ride and Expensive Replacement?