The 2004 Highlander is a solid SUV, but the 3.0L V6 (1MZ-FE) has a critical head gasket weakness that can destroy the engine if ignored, while the transmission oil cooler tends to fail and cross-contaminate fluids. The 2.4L four-cylinder is far more reliable but underpowered for this chassis weight.
3.0L V6 Head Gasket Failure (External Leak)
Common · high severity
Typical onset: 90,000-150,000 mi
Symptoms: Coolant seepage or dripping from front of engine, visible below intake manifold, Sweet coolant smell from engine bay, especially when warm, Gradual coolant loss requiring top-offs every few weeks, White crusty buildup on front engine block near timing cover
Fix: Both head gaskets must be replaced as a pair—this is not a one-side job. Requires removing intake plenum, exhaust manifolds, timing belt, and both cylinder heads. Machine shop resurfacing of heads is mandatory to prevent repeat failure. Smart shops replace timing belt, water pump, cam seals, and valve cover gaskets while in there. 12-16 labor hours depending on shop efficiency and whether heads need excessive machining.
Estimated cost: $2,800-4,200
Transmission Oil Cooler Failure and Fluid Cross-Contamination
Occasional · high severity
Typical onset: 120,000-180,000 mi
Symptoms: Strawberry milkshake appearance in transmission fluid (pink and frothy), Chocolate milk appearance in radiator or coolant reservoir, Transmission slipping, delayed engagement, or erratic shifting after cooler fails, Overheating transmission or engine temperature spikes
Fix: The internal transmission cooler inside the radiator develops pinhole leaks, allowing coolant into ATF and vice versa. Once this happens, the transmission is often damaged beyond repair. Full fix requires new radiator, complete transmission fluid flush (or full rebuild if contamination sat for any time), and new external auxiliary cooler recommended. If caught early (within days), a flush may save the trans—if driven for weeks, you're looking at a rebuild or replacement. 8-10 hours for radiator and external cooler install with thorough flush; add 18-25 hours if transmission needs rebuild.
Estimated cost: $1,200-1,800 if caught early; $3,500-5,500 with transmission rebuild
Lower Engine Sludge Buildup (3.0L V6)
Occasional · high severity
Typical onset: 80,000-140,000 mi
Symptoms: Knocking or ticking noise from lower engine on cold starts, Oil pressure warning light flickering at idle when hot, Excessive oil consumption (more than 1 quart per 1,000 miles), Engine seizing or spun bearing if oil starvation occurs
Fix: The 1MZ-FE is notorious for sludge if oil changes were extended beyond 5,000 miles or if lower-grade oil was used. Sludge clogs oil passages and starves bearings. If caught before bearing damage, aggressive engine flushes and short-interval oil changes (every 1,000 miles for 3-4 cycles) can help. If bearings are damaged, you're looking at short block replacement or full rebuild with new pistons, rings, bearings, and crank polishing. 20-28 hours for short block swap.
Estimated cost: $500-800 for flush treatment attempts; $4,500-6,500 for short block replacement
Front Lower Control Arm Bushings
Common · medium severity
Typical onset: 100,000-150,000 mi
Symptoms: Clunking noise over bumps from front suspension, Steering wander or vague on-center feel, Tire feathering or uneven inner-edge wear on front tires, Visible cracking or tearing in rubber bushings during inspection
Fix: The front lower control arm bushings deteriorate and crack, especially in rust-belt climates. Most shops replace the entire control arm assembly rather than pressing new bushings, as the arms are affordable and save labor. Both sides should be done together. Includes alignment afterward. 3-4 hours for both sides plus alignment.
Estimated cost: $600-950
Rear Subframe and Differential Carrier Bushing Deterioration
Occasional · medium severity
Typical onset: 110,000-160,000 mi
Symptoms: Clunking or thudding from rear on acceleration or deceleration, Vibration felt through chassis at highway speeds, Rear axle feels like it's shifting or walking sideways over bumps
Fix: The rubber bushings that mount the rear differential carrier and subframe degrade and collapse. Requires subframe drop to access and replace bushings—not a DIY job. Some shops use polyurethane aftermarket replacements for longevity. 4-6 hours depending on rust and bolt seizure.
Estimated cost: $700-1,200
Accelerator Pedal Position Sensor / Throttle Body Issues
Occasional · medium severity
Symptoms: Check engine light with P0120, P0121, or P2138 codes, Intermittent throttle hesitation or surging, Limp mode activation with reduced power, Pedal feels sticky or has inconsistent response
Fix: NHTSA had multiple recalls for accelerator pedal issues, but even post-recall, the pedal position sensor and electronic throttle body can develop faults. Cleaning throttle body and relearning idle often resolves minor cases. Sensor replacement or throttle body replacement required for persistent faults. 1.5-2.5 hours for throttle body; 1 hour for pedal sensor.
Estimated cost: $350-700
Owner tips
If buying a 3.0L V6 model, insist on visual inspection for coolant leaks at front of engine and verify oil change history—sludge kills these engines.
Check transmission fluid color immediately; if it's anything but bright red, walk away or budget for a transmission.
Use only Toyota-spec coolant (red long-life) and change it every 50,000 miles to reduce head gasket failure risk.
The 2.4L four-cylinder is significantly more reliable but lacks power for highway merging and passing with a full load.
Buy the 2.4L four-cylinder model if you can live with modest power, or budget $3,000-5,000 for inevitable head gasket and cooler work on the V6—otherwise, look at the 2005+ with the 3.3L V6 instead.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
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Every control module on the 2004-2007 Toyota Highlander — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Optional equipment; sensor calibration may be required
Back Monitor Camera ECU (CAMERA ECU)0.6 hr R&Rno coding
📍 Rear cargo area, integrated with camera assembly or behind trim
⚠️ Optional equipment on 2006-2007; plug-and-play
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
TOYOTA IS RECALLING CERTAIN MODEL YEAR 2004 AVALON VEHICLES; 2004 AND 2005 CAMRY, CAMRY SOLARA, HIGHLANDER, AND SIENNA VEHICLES, 2006 HIGHLANDER HYBRID; 2004 AND 2005 LEXUS ES330 AND RX330; AND 2006 LEXUS RX400H VEHICLES MANUFACTURED FROM JUNE 1, 2004 THROUGH MARCH 31, 2005, EQUIPPED WITH THE 1MZ-FE OR 3MZ-FE ENGINE. THE AMOUNT OF ADHESIVE AGENT APPLIED BETWEEN THE OUTER RING AND THE TORSIONAL RUBBER DAMPER (INNER RING) IN THE CRANKSHAFT PULLEY MAY BE INADEQUATE. IF THE ADHESIVE IS INSUFFICIENT, THERE IS A POSSIBILITY THAT THE OUTER RING MAY BECOME MISALIGNED AND IT MAY NOT PROPERLY ROTATE WITH THE INNER RING, CAUSING NOISE AND/OR ILLUMINATION OF THE BATTERY DISCHARGE INDICATOR LIGHT.
Consequence: IN SOME CASES, THE BELT FOR THE POWER STEERING PUMP MAY BECOME DETACHED FROM THE PULLEY WHICH COULD RESULT IN A LOSS OF POWER STEERING AND A SUDDEN INCREASE IN STEERING EFFORT, INCREASING THE RISK OF A CRASH.
Remedy: TOYOTA WILL NOTIFY OWNERS, AND DEALERS WILL CHECK THE CRANKSHAFT PULLEY TO IDENTIFY WHETHER IT WAS PRODUCED BY THE U.S. SUPPLIER. IF SO, THE DEALER WILL REPLACE THE PULLEY WITH A NEW ONE AT NO CHARGE. THE SAFETY RECALL IS EXPECTED TO BEGIN DURING EARLY JANUARY 2012. OWNERS MAY CONTACT TOYOTA AT 1-800-331-4331.
TOYOTA IS RECALLING CERTAIN MODEL YEAR 2004-2006 HIGHLANDER, HIGHLANDER HYBRID, AND MODEL YEAR 2004-2007 LEXUS RX330, RX350, AND RX400H VEHICLES. IF THE FORWARD RETENTION CLIP USED TO SECURE THE FLOOR CARPET COVER, WHICH IS LOCATED IN FRONT OF THE CENTER CONSOLE, IS NOT INSTALLED PROPERLY THE COVER MAY LEAN TOWARD THE ACCELERATOR PEDAL AND INTERFERE WITH THE ACCELERATOR PEDAL ARM.
Consequence: IF THIS OCCURS, THE ACCELERATOR PEDAL MAY TEMPORARILY BECOME STUCK IN A PARTIALLY DEPRESSED POSITION RATHER THAN RETURN TO THE IDLE POSITION. A STUCK ACCELERATOR PEDAL MAY RESULT IN UNINTENDED AND SUSTAINED VEHICLE SPEEDS AND MAKE IT DIFFICULT TO STOP, INCREASING THE RISK OF A VEHICLE CRASH.
Remedy: DEALERS WILL REPLACE THE FLOOR CARPET COVER WITH A NEWLY DESIGNED ONE FREE OR CHARGE. THE SAFETY RECALL IS EXPECTED TO BEGIN DURING MARCH 2011. OWNERS MAY CONTACT TOYOTA AT 1-800-331-4331.
SERVICE BRAKES, HYDRAULIC:FOUNDATION COMPONENTS:MASTER CYLINDER · 10V499000
2010-10-21
TOYOTA IS RECALLING CERTAIN MODEL YEAR 2005-2006 AVALON, MODEL YEAR 2004-2006 HIGHLANDER, MODEL YEAR 2004-2006 LEXUS RX, AND MODEL YEAR 2006 LEXUS GS AND IS VEHICLES. BRAKE FLUID CONTAINING POLYMERS IS USED THAT ACTS AS LUBRICANTS FOR CERTAIN BRAKE SYSTEM COMPONENTS. IF REPLACEMENT BRAKE FLUID IS USED THAT DOES NOT CONTAIN SUCH POLYMERS, OR THAT CONTAINS ONLY SMALL AMOUNTS, A PART OF THE RUBBER SEAL LOCATED AT THE REAR OF THE BRAKE MASTER CYLINDER MAY BECOME DRY, AND THE SEAL MAY CURL DURING MOVEMENT OF THE PISTON. IF THIS OCCURS, A SMALL AMOUNT OF BRAKE FLUID COULD SLOWLY LEAK FROM THE SEAL INTO THE BRAKE BOOSTER.
Consequence: A LEAK OF BRAKE FLUID COULD LEAD TO A CHANGE IN BRAKE PEDAL FEEL AND OVERTIME A DEGRADATION IN BRAKING PERFORMANCE INCREASING THE RISK OF A CRASH.
Remedy: DEALERS WILL REPLACE THE SEAL WITH A NEWLY DESIGNED ONE. THIS SERVICE WILL BE PERFORMED FREE OF CHARGE. THE SAFETY RECALL BEGAN ON NOVEMBER 15, 2010. OWNERS MAY CONTACT TOYOTA AT 1-800-331-4331 AND LEXUS AT 1-800-255-3987.
ON CERTAIN SPORT UTILITY AND HYBRID VEHICLES, THE TWO RETAINING CLIPS FOR THE DRIVER'S SIDE FORWARD CENTER CONSOLE CAN BECOME LOOSE. IF BOTH CLIPS SEPARATE FROM THE FLOOR CARPET COVER, THE COVER MAY LEAN TOWARD THE ACCELERATOR PEDAL, CAUSING INTERFERENCE WITH THE ACCELERATOR PEDAL ROD.
Consequence: THIS CONDITION MAY INTERFERE WITH THE ACCELERATOR PEDAL RETURNING TO THE IDLE POSITION INCREASING THE RISK OF A CRASH.
Remedy: DEALERS WILL REPLACE THE TWO FLOOR CARPET COVER RETAINING CLIPS FREE OF CHARGE. THE RECALL BEGAN ON JULY 24, 2006, AND SHOULD BE COMPLETED BY EARLY SEPTEMBER 2006. OWNERS MAY CONTACT TOYOTA AT 1-800-331-4331 OR LEXUS AT 1-800-255-3987.
LATCHES/LOCKS/LINKAGES:DOORS:LATCH · 04V181000
2004-04-15
CERTAIN SPORT UTILITY VEHICLES HAVE A CHILD PROTECTION LOCK (CPL) SYSTEM ON BOTH OF THE REAR SIDE DOORS. WHEN AN OPERATOR OF THE VEHICLE CLOSES THE DOOR VERY HARD WITH THE CPL LEVER SET TO THE LOCK POSITION, THERE IS A POSSIBILITY THAT THE LEVER MAY CONTACT THE BODY PANEL, CAUSING THE CPL LEVER TO MOVE INTO THE UNLOCK POSITION.
Consequence: THIS CONDITION COULD ALLOW THE DOOR TO BE OPENED WITH THE INSIDE WHILE THE OPERATOR BELIEVES THAT THE CPL WAS ACTIVATED. IF THE DOOR WERE OPENED FROM THE INSIDE WHILE THE VEHICLE WAS IN MOTION, AN OCCUPANT COULD FALL OUT AND BE INJURED.
Remedy: DEALERS WILL SHORTEN THE CPL LEVER. OWNER NOTIFICATION BEGAN MAY 7, 2004. OWNERS SHOULD CONTACT TOYOTA AT 1-800-331-4331.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2004 Toyota Highlander 2.4L I4 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.