Toyota Sienna

The Sienna is a minivan manufactured at Toyota Motors in Indiana from 1997 to the present. This vehicle received a “Top Safety Pick” award from the IIHS (Insurance Institute for Highway Safety).

3,000 Questions
Check Engine Light
Toyota Sienna

How do you reset the 2004 Toyota Sienna check engine light?

unattach the battery for a few minutes and then reattach. it will reset itself if there was just a gas cap issue.

I have a 2004 Sienna. The "Maint Reqd" light came on at exactly 7500 miles. I saw it. A check of the maintenance manual shows that an oil change should be done every 7500 miles. Coincidence? I think not.

(Yes, the dealer may recommend every 3000 or 5000 miles, but Toyota recommends 7500 for most drivers.)

Any guesses on how to reset it would be appreciated.

I called my local dealer after the "maint reqd" light came on and was told how to reset it. With the key in the off position, hold in the trip odometer reset button and turn the key to the run position without starting the engine. Continue to hold the button for 3 to 4 seconds and then release the button. This resets the maintenance light, I don't know if it works for the service light or not. It's woth a try!

you need to make sure that the odometer is in the normal setting (not on one of the tripmeter settings.

First, if it was the gas cap, just tighten it and it will reset itself in the next 100 miles or so. If it is something else, like a leaky gas cap it will never reset. But to reset the OnBoardDiagnostic (OBD)Computer... Go to eBay and search "obdII" and buy one, they run about $50.00 including shipping. There are two types, ISO for Chrysler and some Japanese, and the other one for all the others like Ford and GM. There are several that are both, that is the kind you want. Be sure to email the eBay seller and ask if it is used with your year and model. (1996 was a changeover year for OBDII technology, so this advice may not apply to everybody--but the dealer service guy can tell you over the phone--ask him if it is OBDII compliant.) When you get it, you just plug it in and let it cycle 4 or 5 times and it resets everything. You then have to drive your car for 50 to 100 miles for the onboard computer to test everything, and in the meantime your car will fail smog checks because it has no history in the computer and the smog test procedure demands a history even if there is no pollution. Cut and Paste for a list of them for sale on eBay. Most units come with a list of generic fault codes so you can tell what the problem is, this could be very helpful.

My 1999 Sienna had flat tire light. Found low air in tire, sears pluged hole & filled up to 32#. Can not reset light. 1-Week later ABS light is on too. Week later engine light is on also. Took it to the dealer, they said I had bad cat converter. I had them reset the engine light and it's been off for 35 days now. Car has always ran fine & ABS & flat tire light still on?? Freind of mine has changed his cat converter once since under warrenty & I think it's a faulty signal.

the response about the trip meter is correct, but the instructions on resetting the light are detailed in the manual. Try the manual first and save yourself some time.

Toyota Sienna

What is the law of conservation of energy?

The law of conservation of energy is that energy cannot be created or destroyed, but it can be transferred or transformed from one form to another (including transformation into or from mass, as matter). The total amount of energy in a closed system never changes.

Energy in a system may be transformed so that it resides in a different state. Energy in many states may be used to do many varieties of physical work. Energy may be used in natural processes or machines, or else to provide some service to society. The generic name for a device which converts energy from one form to another is a transducer. Energy transformations in the universe over time are generally characterized by the various kinds of energy available since the Big Bang, including gravitational energy and electromagnetic waves.

Example: Suppose you push a book across a table. The book has kinetic energy but its motion decreases as it slides. It seems like the book's energy is being lost. Actually, the kinetic energy is not lost, it just changes form. The kinetic energy is converted by friction into thermal energy, another form of energy. The thermal energy makes the book, the table, and the air a little warmer.

(see the related link below)
Energy cannot be created or destroyed - it can only be converted from one form to another.

Car Sounds
Toyota Sienna

Engine still makes noise after turning off?

It is called pre-ignition, find a friendly mechanic.

Toyota Sienna
Web Hosting

Will there be any new options available on the 2005 Toyota Sienna?

I am part of the team who builds the current 3.3 litre 3mz v6 engine for the Sienna van. Currently, minor changes are underway for a new v6 engine for the Sienna as well as the Lexus RX 330. Although model changes won't take place (I believe) until 2006, I would not be suprised to see some minor option changes offered in the meantime. You may want to check with your local dealer. Here are more answers and opinions from other FAQ Farmers: * There are rumors of a hybrid option, but I am sure this will have extremely limited production. * In 2005, all models come with steering wheel audio control.

Headlights Tail and Brake Lights
Toyota Sienna

How do you replace the tail light fuse on a Toyota Sienna?

eassy pull the fuse box cover off turn it over located the tail light fuse pull it out replace with same amp fuse

Chevy Tahoe
Toyota Sienna
Ford Expedition XLT
Car Buying

Will the 2005 Sienna have 'fold-into-the-floor' second row seats?

I do believe so. If I recall the 2004 Sienna already has fold in floor seats. No, I believe that Toyota is saving that underflow space for equipment associated with the expected hybrid drive sienna. The second row seats do not fold into the floor only the third row seats. Underneath the second row seats is the spare tire.

Toyota Sienna
Dieting and Weight Loss
History of England

How are onions good for us?

GOOD Onions are known as a medicine. They not only block cancer dramatically, lower cholesterol, thin the blood and warn off blood clots but they also fight chronic bronchitis, infections, hay fever and asthma. It is also known that onions calms animals down. An owner of a large group of old world primates said that she relies on onions to keep her primates healthy during the winter. Especially when primates have been exposed to viruses or when your monkey is in a lot of stress, onions can be the solutions. BAD Besides the fact that they may promote gas, onions raw or cooked can cause Heinz body anemia when overeaten. While eating onions (but also turnip, cabbage, garlic, ...), red blood cells get destroyed and this causes anemia. However, red blood cells get regenerated all the time and a number of red blood cells have to be destroyed before this happens.

Transmission Fluid
Toyota Sienna
Late Model 1979-New Ford Mustangs

What type of transmission fluid does a 2002 Toyota Sienna CE need?

It usually tells you right on the dipstick, this model takes dexronII.

Toyota Sienna

When was the 2005 Toyota Sienna available for ordering?

Looks like they started arriving at dealerships in Sept.

Toyota Sienna
Present Tenses

When will the 2005 Toyota Siennas arrive? The 2004 2005 Toyota Sienna is NOT redesigned for 2004 2005, it is a CARRYOVER from 2002. The Sienna has three trims. These trims are the CE, LE, and the XLE. All trims are equipped with a 210-horsepower, 3.0-liter, V6 engine that provides 19-mpg in the city and 24-mpg on the highway. Overdrive is standard in a 4-speed automatic transmission. The Toyota Sienna is a mini van. The Sienna is a 4-door seats up to 7 passengers. A CALL to your local Toyota dealer should get an answer. THEY HAVE ARRIVED!

Spark Plugs and Wires
Lexus GS
Toyota Sienna

How do you change the three back spark plugs on a 1999 Toyota Sienna?

Yes, changing out the spark plugs on Toyota's tranverse mount V6 engines is tough. I have a 2002 Sienna which is similar to all models 2003 and prior. The front 3 plugs are easy. But the back 3 are really tough to reach.

2001 and prior Siennas only need the Denso platinum plugs PK20TR11 which I think are dual head plugs. But older Siennas can probably still benefit from pricier iridium plugs because they fire more consistently at lower voltage and can take higher temperatures than platinum. I did some research on the web, and folks are raving about Denso Iridium Power IK20s. They are a bit more than the NGKs, but on eBay, I found a set of 4 for just $33-buy-it-now in CA. So I bought 3 sets (12 plugs total).

Tools you'll need - a common 3/8 inch square rachet socket driver. The overall length must not exceed 8 inches inches long and mine is a cheap one from any store. But I would recommend that the rachet have a push button socket release and a fine tooth rachet that clicks every 15 degrees. Next, you need a med-long extension. The spark plug is deep in the tube and you'll need ideally, 5 3/4 inches and no more than 6 1/2 inches max. Of course you need a standard spark plug socket. Additionally, you'll need a 5mm Allen wrench. and lastly, a 10 mm closed-end crescent wrench. Length should be no longer than 7 inches.

Installation: pop the hood, and remove the plastic engine cover. I assume you know how to remove the front plugs. So I'll only focus on the rear plugs.

Start on the right side. Unclip some of the vacuum hoses and spread them out to the sides of the opening. You should see a hole that extends back underneath the air intake and next to the exhaust manifold. Reach back there with your arm. feel for a 1 inch square block and securing hex bolt. Using feel only, use the 10mm closed-end box wrench and loosen the securing nut. A hard counterclockwise tweak should break it loose, and about a half dozen more small loosening motions should loosen the bolt so you can switch out and use your fingers. Remove the bolt and place it away from the engine in a safe place. Lift the boot assembly out. Watch to make sure the rubber grommet doesn't slide off and fall in the oblivion never to be found.

WithOUT the rachet driver, get the socket and extension and slide down tube, then reach in with rachet and unscrew the spark plug. Remove the rachet, and lift extension and spark plug out. If your socket doesn't grip the spark plug, take it out, wrap the lip with a little masking tape). Installation is the reverse of removal.

Get a new spark plug. Slide it inside the spark plug socket and make sure it grips but not too tightly. The plugs are pre-gapped at the factory and have a plastic sleeve to protect the head. You must NOT allow the plug to drop down the tube because the impact could bend the tip and affect the gap or damage the plug.

There are two metal compression washers on the spark plug. There's no room for a torque wrench back there, so tighten the plugs down until the compression washers just begin to feel like bottoming out. Then twist another 30 deg. Do NOT slide the boot/coil assembly back over the spark plug yet. The first boot must remain out from its tube to allow the second boot room for removal.

The middle boot assembly is a bit harder. It's just like the first, but you need to disconnect the wire harness clip to each boot/ignition coil.. With a single hand, rock the boot assembly a little until it lifts up and off the plug about 1 inch. Then turn the boot assembly clockwise a little and use the technique you practiced to unclip the wiring harness from the boot assembly. There is only room for one hand in there. Be persistent and follow technique and practice. Eventually, you should be able to get the wire clip off.

Now the boot/coil should lift out easily. Then use the spark plug socket and reach back in there and slide the socket down the tube and then attach the rachet driver and remove the spark plug. Installation the reverse of removal. Again, be careful about dropping any parts down into the engine.

The 3rd boot is like the 2nd, because you need to disconnect the wiring clip, but it's different in that instead of reaching in from the right side, most of the extraction uses the opening from the left side.

My dealer claims this can take 2 hours of labour. I used simple tools and did all six myself in 1 hour 15 minutes making lots of little mistakes. If you follow these directions and have simple tools and do not exceed my dimension recommendations, you should be able to get in there and do this in under 45 minutes. Good luck.

For more information on this and related procedures please visit:


After posting my original answer to a question on a different forum, I've noticed how started posting this blog. So I thought I'd add comments here. Well, I had to change my plugs again... putting lots of miles on the Sienna. This time I did this in just 45 minutes! The one danger I'd advise here is the pulling of spark plug wires. I recommend that folks use plenty of spark plug lube on the heads to avoid sticking over time and easier removal the next time you gotta do this.


Another reader comments: If you remove the windshield wiper cowling and tray, things are easier (but not easy) to access. I was able to change the plugs on my 2002 Sienna without removing any hoses or anything, just a ground wire that was in the way. To do this:

1. The engine should be cold. Open hood. Remove caps at base of wipers, remove wiper nuts, and wriggle off the wipers.

2. With needlenose pliers, squeeze the plastic holddown thingies under the front rim of the wiper tray, while pulling up on the gasket that runs along the top (hood gasket). Start at one end and work across until the gasket is removed. Remove wiper cowling by pulling up and towards the front of the car. There were 2 plastic holddown thingies on the sides that I couldn't remove, they just broke off. Disconnect wiper washer hose at connector on passenger side, remove hose from clips in tray, and lift out both cowling pieces.

3. Undo bolts holding the wiper tray, but not the two bolts on the front of the tray near the air filter (these hold the wiper motor assembly to the bottom of the tray).

Don't set the bolts in the tray, they could roll down a drain hole into the engine compartment. Lift the tray as far as you can (it's heavier than you would expect).

Disconnect the wiper wiring connector and push the wiring cable harness thing out of it's hole. Now you can remove the tray.

4. Remove the fresh air intake duct (for the passenger compartment, not the engine) by removing 3 plastic nuts.

Now you can actually see and reach the rear part of your engine. Since the spark plugs are all under the intake manifold, you pretty much have to work by feel. You can reach under it from either side once you remove the ground wire attached to the intake manifold assembly on the passenger side. (It's pretty obvious which wire, because it's in your way). With the proper selection of socket extensions, and lots of patience, you can replace the spark plugs without removing anything else, except for that little plastic cover on top of the engine.

Windows and Mirrors
Toyota Sienna

How do you replace the passenger side mirror of 2000 Toyota Sienna?

It really isn't that bad. First remove the door panel. (The connector for the mirror is behind the panel just to the left of the door handle.) The arm rest cover pops off by gently prying upward at the corners near the door panel and along the outer edge of the arm rest. Then remove the 2 screws. Remove the screw that holds the door handle bezel on. Remove the little plastic plug to the left of the door handle as well. This reveals yet another screw to remove. Now you can gently pull the door panel away from the door. The little plastic clips will pop out of the door. If they come away from the door panel they easily fit back in place in the metal retainers built into the door panel. You can now disconnect the connector and remove the 3 10mm mirror bolts.

With respect to the door handle bezel on the inside of the door, to remove it you must pull/slide the bezel away from the door hinge. It should move an 1/8 to 1/4 inch. There is a little tab that hooks inside the door handle mechanism and two small holes, top and bottom, that slip over little pegs on the mechanism. I broke this tab while removing the bezel on my car. This was the most difficult part, on my car, to remove.

Getting the door handle bezel off is definitely the most mysterious part of removing the door panel, but it's easy if you know exactly what to do!

The previous post implies that you can slide the bezel toward the rear. This can only be done AFTER the two tabs that are mentioned are disconnected from the round pegs that they are connected to. The pegs are only about 1/32 of an inch high, and are part of the door handle mechanism. They are on the vertical axis of rotation of the door handle and lock button. One peg is just above the lock button, and the other is just below the door handle. The two tabs that engage these short pegs are part of the bezel. You can disconnect the tabs from the pegs with a thin screwdriver. Slide the screwdriver between the upper side of the lock button and the bezel, just behind the axis of rotation of the button. Pry up the tab by pushing the screwdriver handle DOWN, lifting the tab off the upper peg, and pull the top edge of the bezel away from the door panel. Do the same thing between the lower edge of the door handle and the bezel, pulling the screwdriver handle UP to disengage the tab from the lower peg, and pull the bottom side of the bezel away from the door panel.

Now the bezel moves easily. Wiggle it a little toward the rear of the car to disengage the remaining tab, which is about 1 1/4 inches forward of the screw hole, and fits into a slot in the door handle mechanism.

Toyota Sienna

How do you reset check engine light for Toyota Sienna?

My check engine light recently came on as well. Make sure you diagnose and fix the problem before you just reset the light. Just because the light goes away does not mean there is still not a problem. I got an <a href="">OBDII scanner</a> and it is simple to use and may save you a lot of money throughout your life. I hooked it up to my car and found out that it was just the gas cap. The scanner cleared the light for me and i replaced the gas cap. No more issues! Hope this helps, good luck!

Toyota Sienna

Does the tow prep prg on 2010 sienna include the hitch?

No, the tow prep package includes an engine oil cooler. All siennas already have a transmission cooler and 130amp alternator. You will need wiring and the actual hitch, which attaches with 6 bolts.

Toyota Sienna

Any restrictions or rules to follow when using cruise control to pull a 4x8 trailer with a 2002 Toyota Sienna? Gross Vehicle Weight Rating 5,247lbs. Curb Weight 3,919lbs. Max Trailer Weight 3,500lbs. well, ya start here, dont over load the hitch with tooo much tongue weight, then read the owners manual about cruise. No manual, call the dealership and ask, they should know. Common sense will take you a long way.

Also =

Most manuals recommend that while towing, you turn your overdrive OFF and DO NOT use cruise control. It puts unecessary stress on your engine and drivetrain.

Car Batteries
Toyota Sienna

Can you buy a replacement battery for a Toyota Sienna at Costco?

If they sell batteries, then yes.

Toyota Sienna
OBD Diagnostic Codes

How do you read the ODBII diagnostic codes for a 2001 Toyota Sienna?

chilton auto repair manual available free at your local public library. vid i have a 2001 Sienna with the check engine light on. had a diagostic machine check and got a code P0171 AND P0174. And it says "system too lean". Also it the diagnostic reads: O2S212 .625 mv O2S211 3.29 mv your info will be greatly appreciated. po 171 is almost always the mass airflow sensor located in the air cleaner box. start with that, its only about 150.00 for the part and is easy to replace. I took MAF off the top of the air filter with two screws and clean it and reset the check engine with ODBII code reader I called Toyota dealer in Canada it cost $245 plus tax

P0171 specifically for Toyota is generic "too lean", and very well could be MAF, but the MAF can be cleaned, recommend trying aerosol cleaner before buying a new one, and run the OBD again to see if it will give you a more specific fault could be O2 sensor, MAP Intake (Manifold Absolute Pressure) and dozens of other things. No dispute here, just adding

you can choose china brand Launch X431 Creader VIII CRP129 from, it is designed to almost vehicle, and read the ODBII diagnostic codes, als have others car diagnosis function, it is an good diy tools for owner, diagnosis and maintenance easier and cost even less. Maintenance and Service All in One, Because it has more application, like Engine Oil Reset, ABS Bleeding, and more.

Toyota Camry
Toyota Sienna
Toyota Tacoma

Where is the tire pressure sensor located for a Toyota Sienna and how do you determine if it is gone bad?

I believe that it senses the drag from the flat tire through the axials. Try release some (1/3) of the air from one tire (rear)then drive for about 10 minutes, upto 40mph speed and see if the light goes on. I had a nail in the tire and both times it did indicated that the tire is low on air. Note, the light goes on after you driven.

I'm not an expert on this, but I think that it uses the ABS system, and measures the numbers of revolutions of each tire. If one tire is spinning faster that the other 3, it must have less air (or you are making a lot of left hand turns).

it does work by reading the abs sensors and turning on the light when one wheel is moving faster than the others. however it cannot detect which tire because it actually compares the average of the 2 front sensors to the average of the 2 rear sensors. this eliminates the possibility of error based on a car that is turning one direction or the other for an extended period of time. you know it wont work if the abs light is also on because that would preclude the pressure sensing system from working. otherwise, start by making sure the pressures are correct for all 4 tires( the spare doesnt matter for this van) then turn the key on, locate the tire pressure light reset button on the dash to the left of and below the steering wheel. hold the button down until the low pressure light flashes 3 times. if it doesn't flash but only goes out, turn the key off then on again and hold the button until it flashes 3 times. if it does not flash, there is something wrong and it needs to be checked by a dealer.


Nope on all three. I just topped the rear tires while the vehicle was idling and the sensor went out while I was adding air. Both rear tires were at 32 and I filled them to 36 on a cold day. Front tires were already at 36.

NOPE to all four, and even the last " " did not the original question. The 1st three people sounded like they were literally guessing and have no clue...if you don't not give bad information.

1. Where is the tire pressure sensor located for a Toyota Sienna: The actual sensors are integrated into the valve stems, the small valave where you add air to your tires. You have to remove the tire from the rim seatinig bead and replace the whole valve stem assembly if they go bad with an EXACT part number. They record the pressure inside the tire and wheel assembly and talk back to the vehicles computer using specific frequencies.

2. And how do you determine if it is gone bad? The biggest reason for them to stop working is that they get damaged during a tire swap or removal. You can have the vehicle scanned to usually show the faults. A used sensor can usually be bought for $20-40. If your receiveing side of the computer/body module is good and your tire pressure is per specification, that sensor is bad. Look in your owners manual and set all your tires to the reccomended mean pressure. Once your pressures have been set most Toyota's have a reset button (Avalon is under the drivers knee area, so are most Sienna's but I did not see a year stated) or try disconnecting the battery for 60 seconds. Turn your key to accesory position amd push reset button for about 5 seconds to reset (engine should not be running). Sometimes it takes a few minutes of driving to fully reset and remove the warning light. There is usually a good youtube video showing the exact procedure as each make and model are different

Acura RL
1995-1999 Dodge & Plymouth Neons
Toyota Sienna

Is the procedure to reset the Maintenance Required light on a 2005 Toyota Sienna the same as for the 2004?

It should be. I don't think there were any major changes in this regard from '04 to'05, but check your owners manual or the dealership to be sure. It is the same (but you won't find the procedure in the owner's manual). It is in the owners manual. ed724

Toyota Corolla
Toyota Sienna
Grand Am SE

How do you reset the maintenance required light on a 2005 Corolla since the owners manual doesn't say how to do it?

Turn ignition key to 'ON' and press the odometer button until the display reads actual mileage... not Trip A or B.

Turn ignition key to OFF.

Hold in the same button you used in step 1.

While holding the button in, turn ignition key to 'ON'.

ODOMETER will change to

5 dashes - - - - -

Then 4 dashes - - - -

Then 3 dashes - - -

Then 2 dashes - -

Then 1 dash -

THEN all zeros 0 0 0 0 0

Then back to the correct mileage

The 'Maint Reqd' light should blink and go out.

Toyota Sienna

How do you remove the rear bumper cover on a 2003 Toyota Sienna?

The rear bumper cover is attached by 4 screws (behind the fender well covers, easily moved), and 4 screws inside the rear hatch. There are also 12 fasteners along the top and bottom of the bumper skin that can be pried out. Replacement fasteners cost about 5-10 dollars for a pack of 10. If you have a gray (non-painted) rear bumper, it only costs about $200 to replace it, and it's easily a DIY job.

Oil and Oil Filters
Toyota Sienna
Ford Explorer Eddie Bauer
Ford Explorer Limited

How do you reset the maintenance required light on a 2004 Sienna that blinks longer at start up when oil change is due?

I was looking for this same answer and found it on another site and it worked. here is the answer. The system must be reset after the engine oil replacement. Reset the system by the following procedure:

1. Turn the ignition key to the "OFF" position with the odometer reading shown.

2. Turn the ignition key to the "ON" position while holding down the trip meter reset button. Hold down the button for at least 5 seconds. The odometer indicates "000000" and the light goes off.

Toyota Sienna

What size is the subwoofer in a 2004 Toyota Sienna XLE? says 8" sub.

Toyota Sienna
Toyota Tacoma
Timing Belts and Chains

What is the procedure for changing the timing belt on a 1998 Toyota Sienna?

Replacing timing belt,Sienna 1998: 1.Disconnect battery (-) cable and plastic wiper washer cowl assembly 2.Remove spark plugs and put all wirings,cables out of the way 3.Drain coolant (cold) and remove upper hose 4.remove front right tire and wheel plastic fender apron 5.jack up engine under oil pan with rubber,towel or wood slightly 6.remove right engine support rod and its bracket 7.remove all drive belts.Examine condition;Label if re-using 8.remove plastic upper timing belt cover & gasket 9.remove crankshaft pulley bolt-use the ff. methods: a.air impact wrench or Toyota Special service tool-best b.chain wrench on pulley then breaker bar/socket on bolt-good fly wheel cover,jam screwdriver on gear teeth then unbolt-tough d.breaker bar/socket on bolt, jam bar tip on floor, lower car then "start" engine -smart 10.remove pulley by hand or use carefully 2 prybars then remove plastic lower T.B.coverand gasket 11.reinstall bolt and turn engine clockwise to align timing marks:one on each camshaft sprocket and one on the crankshaft sprocket 12.remove T.B. tensioner spring-2 bolts loosen alternately then keep upright 13.remove crankshaft sprocket guard then the sprocket, then the belt. 14.Examine belt condition for damage and correct cause of damage if any 15.remove idler T.B.pulleys & check for smooth operation/contamination/leak 16.check all oil seals, water pump leaks,etc 17.Check T.B.tensioner spring for oil leak and tension by pressing push rod against hard object-there should be no movement or leak 18.Compress push rod using vise, align rod hole with outer hole then insert small nail, pin or wire to keep it there then reinstall along with other parts removed 19.Install T.B.carefully.No twist, stretch,prying ,oil, moisture, bending 20.Handturn engine 720 deg.clockwise, feel for resistance , and then see timing marks still re-align 21.Reinstall plastic covers and gaskets,drive belts.etc in reverse order 21.

Toyota Sienna

What are diagnostic codes P0171 and P0174 for a 2001 Sienna?

P0171 and P0174 mean "fuel mixture too lean" on cylinder bank 1 and bank 2 respectively. Sorry I don't know what causes this. Looking at this same problem on 2000 Ford Taurus. Believe it is going to be in the HEGO (Heated Exhaust Gas Oxygen) Sensors. Bank 1 and 2 detecting too lean a condition. Yuck. Per the 1998 official Toyota shop manual for a Sienna, it could be a bad 1) coolant temp sensor 2) bad HO2S (or Fuel/Air sensors) 3) bad mass airflow sensor 4) restricted fuel somewhere (like the fuel filter in the tank! ouch.) First, check to function of the coolant temp sensor. You can pull it and play wiht your stove and boiling water or just buy a Carchip data collector and download the data to your computer to analyze. Second, before you replace that horribly expensive Mass Airflow Sensor, pull it out and *carefully* spray it clean with brake cleaner or an electronic cleaner of some sort. And do NOT touch any of the itty-bitty wires inside with anything or you WILL be replacing it. Third, if you have HO2S sensors, you can check the resistance of them using an multimeter to see if they are within spec. I forget exactly but it's something low like 9-12 ohms at 68F. If you have Fuel/Air sensors instead, it's dealer diagnostic time. Fourth, if you suspect fuel pressure or fuel flow issues, I recommend dealer diagnostic time too. My best friend got severely burned (2nd and 3rd degree on 50% of his body) messing with fuel and his VW bug when we were in high school. 25 years later, he is still covered in scar tissue and will be forever.


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