Toyota

Have Toyota Questions? Ask a Mechanic for Answers ASAP

Ask an Expert,
Get an Answer ASAP!

Toyota

Toyota Sienna LE: 2008 Toyota Sienna. Symptoms: AC system not

Customer Question
2008 Toyota Sienna. Symptoms: AC...
2008 Toyota Sienna. Symptoms: AC system not blowing cold air, AC light blinking on AC Button, Radiator Fans not turning on
Submitted: 2 years ago.Category: Toyota
Show More
Show Less
Ask Your Own Toyota Question
Answered in 3 minutes by:
7/26/2015
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
Your Toyota Guy
Your Toyota Guy, Certified Toyota Master Diagnostic Technician
Category: Toyota
Satisfied Customers: 591
Experience: I have been/am a Toyota technician for 15yrs+.
Verified
The blinking light indicates an electrical failure, the most common cause is the magnetic clutch relay in the under hood fuse box, on the driver's fender. It will be designated on the cover as MG/CL or the like, if you can tell me what color it is I can help further, as certain ones are known to go bad.
Ask Your Own Toyota Question
Customer reply replied 2 years ago
I am not sure if it added everything I have tried:Troubleshooting so far: I have double checked the 7.5 a fuse by the main car ECU, double checked every fuse under the hood, double checked every fuse under the driver’s side foot panel, all fuses match the book and all tested fine. Used a set of AC gauges and low side pressure is 30, and high side is 80 (normal per book) with AC running but AC clutch was not be engaging so I wired past the clutch relay and forced it to activate and the ac clutch engages (still no cold air). I figured maybe it was the AC relay, so I replaced it with the starter relay (identical) and the starter worked fine, and the AC clutch still did not engage on its own when AC was running, ruled out the compressor clutch and magnetic clutch relay. Noticed that the main radiator fans don't turn on when I have the AC running. I knew at least one should turn on when the AC is running to cool the AC condenser and both should run if I disconnect the temp sensor. So I hotwired and tested the two fans, they both worked great (ruled out bad fans). Ran the car for 20 min at 2000 rpm and I have an OBD tester that gives temp and it got to 100C and the fans never turned, they should turn on at 97C based on the official Toyota service manual, which I have on CD with all wiring diagrams. Main car temp gauge worked fine. Because the radiator fans never turned I started to focus on them, knowing that the car could over heat if they don’t work and figure they were related to the AC not being cold with no air flow past the condensers. Tested voltage going to cooling control unit, 13.2 v in with car running, but still no radiator fans. Ohmed out the negative main power supply to the cooling control unit, it was good. Ohmed out the negative from cooling control unit back to the related relay contact, they were good. Replaced the main fan relay and the heater relay with new ones, just because lots of forum posts on them being a common problem. Ran 12v to several other related relays and ohmed out the contacts that close with voltage, they were all good. Looked at all the contacts under related under the main fuse box, they all looked fine. Disconnected the engine temperature sensor (which should kick on both the fans full speed and throw p0118 engine codes, engine codes thrown, but still no radiator fans). Reset codes. Figured it may be the cooling control unit, replaced it with a used one from ebay, fans still did not run. The cooling fan control unit is activated with RF signals from the main car ECU via a Red/Yellow wire. Toyota service manual says replace cooling control unit first and then main ECU if still not working. Since I don’t have a way to test RF signals from the main ECU I ohmed out the red/yellow wire that runs from the cooling fan control unit back to the main car ECU plug, it ohmed out good. Only thing left from my calculations was the main car ECU. Replaced main car ECU with the same make, model, and year from ebay and did the “handshake” method to flash the main car ECU by shorting the TC and CG on OBD port for 30 min, per Toyota directions for replacing ECU with used one. New (used from ebay) main ECU now runs the car just fine after the flash, but still no radiator fans with engine temp sensors disconnected or up to temp. I have the Toyota TIS system on an old laptop, it throws no codes and everything tests fine related to radiators and fan system.The only thing I can guess is the used cooling fan computer, or used main ECU is bad. Bamboozled and befuddled I am out of ideas. I have no idea what else to check to make the cooling fans run. I have wiring diagrams for everything
Customer reply replied 2 years ago
Sorry for all the info after you answered. I entered it when it asked me "what else I had done" but I guess you didn't get that info before you replied.
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
Reading everything..
Ask Your Own Toyota Question
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
Check the red/yellow wire for voltage, specifically 5volt reference.
Ask Your Own Toyota Question
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
When the fans should be running of course.
Ask Your Own Toyota Question
Customer reply replied 2 years ago
I remember checking that also when I was the testing of that section on the cooling fan on vehicle inspection. From what I recall it seemed normal but I will check it again in the morning.
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
Just let me know what you find.
Ask Your Own Toyota Question
Customer reply replied 2 years ago
I do remember checking this before I replaced the cooling fan computer and it was part of the reason I actually replaced the cooling fan computer first, but I just checked it again. 5.5 volts with a warm car running but under temp, 6.12 volts with AC running, 9.09 with temp sensor disconnected. The varied rates make me still think the cooling fan computer was bad. The book does not say anything about the voltage going up but it makes sense and I tested it several times and the rates were about the same each time.
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
Yes, that shows the correct signal from the ECM, you have a bad cooling fan controller.
Ask Your Own Toyota Question
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
Did you get the A/C running?
Ask Your Own Toyota Question
Customer reply replied 2 years ago
replacing the fan control unit, with a 3rd unit did not fix the issue. Still same problems and same symptoms. What is next?
Customer reply replied 2 years ago
Update: I contacted the ebay seller that sold me the original used fan controller (#2) , he sent me another one at no additional charge (#3). The probability of having all three fan ECUs bad is EXTREMELY, EXTREMELY low, as its not a common fail point and statistics would suggest it's nearly impossible. After I put in the new ecu control unit (#3) and it still didn't work i decided to check the red/yellow wire from the main ECU. At the time I believe it was still showing reference voltage like before but still no fans under any circumstance. My wife had complained that there was a high pinched almost non existing ringing noise coming from the computer area ever since I replaced it. Even thought the main ECU I had purchased from ebay was also from a 2008 Toyota sienna SE and it had run fine for the past two weeks I plugged back in the original main ECU and flashed it for 30 min with the "handshake method". The car started fine on the original main ECU but still no cooling fans.Convinced it must be something else I pulled the main power supply plug that goes to the fan ecu control unit and manually plugged each wire into the contacts on the fan ECU, ensuring they were all touching the contacts on the cooling ECU. This actually caused the new unit (#3) to turn on one of the cooling fans (passenger side) whenever I turn on the key to the aux position, even if the AC is off and the temp sensor is plugged in. This is the first I have seen any cooling fans work since this started. The car was cold (67C) however so no fans should have turned on at all. The fan stayed on even if I ran the car for several minutes. I tried the other cooling fan computer (#2) and the same symptoms, just passenger side fan with key to aux. I checked the voltage on the main ECU yellow and red wire, no voltage, even with AC on or Temp Sensor disconnected, now no changes in reference voltage, just zero all the time. I am guessing that when there is no voltage on yellow/red wire the cooling fan computer default is to turn on at least one fan. Figuring that maybe I had blown the AC fuse that was by the main ECU (behind glove box) I checked it, it was fine. I had previously replaced the main Fan relay with a brand new one, but figuring that maybe it was stuck closed I checked it. It was fine. I even switched it out with the original one, and the fan would still turn on whenever I turned on the key. Figuring maybe the #2 fan ECU computer was bad I just put fan controller #1 (original) back in for testing...this time BOTH fans turn on at full blast when I turn on the key with a cold car and no ac and a normal temp sensor plugged in. I seem to have gotten the fans to both work now but now they just stay turned on all the time the key is on.I know what your thinking if you work at a Toyota dealership....why am I using used parts off Ebay? Simple the replacement (Fan ECU #2) was just $35 dollars, and the second one (#3) was free from the original seller. The probability of TWO bad used parts in a row is Extremely low, and now I am not getting any reference voltage so I am not convinced that if I replace the fan ECU at this point with a new dealer one ($300) it will solve the problem.Next I ran a full health check with TOYOTA TIS system to see if I could find anything else. This time TIS it put an asterisk next to the AC system after the test, indicating it could not find the AC system or that something was wrong but did not give more details.Is there anything (fuse/relay) between the main ECU and the red/yellow wire that would cause the wire to have no voltage now? Is there anything else besides a faulty main fan relay (that I already tested/replaced) that would cause both fans to run at full speed as soon as I turn the key to Aux regardless of normal temp/no AC/connected temp sensor? What would cause the red/yellow wire to have no voltage?
Customer reply replied 2 years ago
No reply after two days, that last fix did not solve the problem? If you don't want to answer the questions then please transfer it to someone else as I am nearly 2 weeks into the question....and I don't have a solution yet.
Toyota Mechanic: Your Toyota Guy, Certified Toyota Master Diagnostic Technician replied 2 years ago
Sorry, internet was down. If the CAN bus could not communicate with the ECU and your signal wire (red/yellow) isn't shorted to ground then the ECU is just not responded and needs to be replaced.
Ask Your Own Toyota Question
Customer reply replied 2 years ago
Neither computer, the original, or the replacement, is sending signal to the red/yellow wire and both fans turn on full speed as soon as I turn the car to first position. I have looked at all the wiring diagrams and there is only one wire from the ECU to the fan controller computer and it ohms out fine. When the car is running the red/yellow wire almost ohms out to ground (0.2). I can try and replace the ECU with another one as they are only 20-40 bucks on ebay but two computers....and still no signal from red/yellow wire I am wondering if there is something outside the main computer, that signals the main computer to then send signal to the red/yellow wire. I know I can only flash the immobilizer so many times before I run into big problems...is there anything besides replacing the main ECU again that would cause the red/yellow wire to send signal? I have checked every fues that is at all related and they are all fine....
Ask Your Toyota Guy Your Own Question
Your Toyota Guy
Your Toyota Guy
Your Toyota Guy, Certified Toyota Master Diagnostic Technician
Category: Toyota
Satisfied Customers: 591
591 Satisfied Customers
Experience: I have been/am a Toyota technician for 15yrs+.

Your Toyota Guy is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

THANK YOU, THANK YOU, THANK YOU!! I've got my baby back. Tomorrow I will get a tank of high octane, remove the top, go for a long long ride and enjoy my car. THANK YOU!

JugheadUSA

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

< Previous | Next >

Meet the Experts:

Chris (aka-Moose)

Chris (aka-Moose)

Auto Technician

1,001 satisfied customers

16 years of experience

Marty

Marty

ASE Certified Technician

180 satisfied customers

ASE & Bosch Master Tech. 30 years experience.

Amedee

Amedee

Toyota Technician

1,229 satisfied customers

ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector

Anthony

Anthony

ASE Certified Technician

401 satisfied customers

ASE Master Automobile Technician with over 20 years exp. in this field.

Richard

Richard

ASE Certified Technician

9 satisfied customers

Toyota tech. ASE Certified Technician

Skyvisions

Skyvisions

ASE Certified Technician

12,737 satisfied customers

Toyota Master Diagnostic

Genchi Genbutsu

Genchi Genbutsu

Toyota Master Technician

3,761 satisfied customers

Toyota Certified Master Diagnostic Technician, ASE Master Technician with L1 Advanced Engine

< Previous | Next >

Related Toyota Questions
Had a remote starter installed at a Toyota dealership and
Had a remote starter installed at a Toyota dealership and have had battery problems. It's on a 2014 Camry LE They have now installed a battery charger that sits on top of the battery and turns on when… read more
Toyota Service
Toyota Service
Toyota Dealership Service & CR Manager
1,344 satisfied customers
Where is the starter relay on a 2006 toyota rav 4. 160k.
well i jumped my car and stupidly had the terminals opposite … read more
Jared D
Jared D
Shop Supervisor
Bachelor\u0027s
3 satisfied customers
2010 Toyota tundra 5.7 will not start. Key turns but starter
2010 Toyota tundra 5.7 will not start. Key turns but starter dose not engage, lights on dash blink when key is turned, here clicking in dash when key is turned. Changed starter last year and still hav… read more
baddad1
baddad1
technician
High School or GED
5 satisfied customers
Won't start. Doesn't click. New battery and starter tested
Won't start. Doesn't click. New battery and starter tested and is fine. When you turn the key lights dim … read more
ted ritter
ted ritter
Team Leader/toyota master tech/retired
High School or GED
2,692 satisfied customers
1996 toyota tacoma replaced radiator, water pump, thermostat
1996 toyota tacoma replaced radiator, water pump, thermostat 3 times, flushed heater core I get no heat inside cab… read more
roy
roy
Associate Degree
3 satisfied customers
1997 Toyota Corolla 1.6l automatic. The starter keeps
1997 Toyota Corolla 1.6l automatic. The starter keeps turning even if the ignition switch is off or key is out. Just replaced third starter. I believe its the starter relay but I can't find where it i… read more
ted ritter
ted ritter
Team Leader/toyota master tech/retired
High School or GED
2,692 satisfied customers
Truck wasn't starting changed battery/starter and now the
truck wasn't starting changed battery/starter and now the starter is continuously running when the truck starts?? … read more
ted ritter
ted ritter
Team Leader/toyota master tech/retired
High School or GED
2,692 satisfied customers
2001 echo doesn't start after running this morning. Starter
2001 echo doesn't start after running this morning. Starter doesn't engage, no clicking. Cleaned terminals, no change, VOM reads 13.9 across terminals. HELP!… read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,410 satisfied customers
I am trying to determine whether I have a starter problem or
I am trying to determine whether I have a starter problem or a starter relay problem. The vehicle is a 2003 toyota tacoma. It has the 2.4 engine and a automatic transmission. Occasionally the starter … read more
baddad1
baddad1
technician
High School or GED
5 satisfied customers
2017 Toyota highlander will not crank the starter. I have a
2017 Toyota highlander will not crank the starter. I have a keyless and a push start button. Message says braking power low … read more
Edward Clayton
Edward Clayton
Associate Degree
1,033 satisfied customers
2004 Avalon radiator cooling fans not coming on, Yes
Yes overheating. I'm not sure which fuses to check. 26, 58, and 59? … read more
Michael Solis
Michael Solis
363 satisfied customers
It will not start. It's not the battery and the starter is
It will not start. It's not the battery and the starter is new … read more
Edward Clayton
Edward Clayton
Associate Degree
1,033 satisfied customers
Overheating. changed radiator, thermostat and sensor.
overheating. changed radiator, thermostat and sensor. headgasket appears fine (oil looks good , no white smoke from exhaust). waterpump is ok. not getting heat. I tested new themostat in boiling water… read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,410 satisfied customers
07 Tacoma starter will not starter. I change park/ neutral
07 Tacoma starter will not starter. I change park/ neutral safety switch … read more
Skyvisions
Skyvisions
ASE Certified Technician
High School or GED
12,737 satisfied customers
1999 Camry may or does need a radiator replaced. But,
1999 Camry may or does need a radiator replaced. But, question is: Coolant container has a half inch hole its top, and car is being loaded with gallon of water 2-3 times a day. Now the car is stuter s… read more
Joecamel90
Joecamel90
Technician
Associate Degree
24 satisfied customers
I replaced the radiator and thermostat...tried bleeding
I replaced the radiator and thermostat...tried bleeding radiator...still running hot. The condenser fan stopped working...would this cause it to run hot? … read more
Matt
Matt
Engineer
Bachelor\u0027s Degree
5 satisfied customers
Battery was dead. Tried to charge it with engine starter on
Battery was dead. Tried to charge it with engine starter on charger. Click, click nothing cranking it. No lights on dash or current going anywhere. Trunk won't open. Like a fuse is blown. I tried a ju… read more
Tool Hut
Tool Hut
Owner
519 satisfied customers
Gas engine starter not starting, not a gas hog starter not
Gas engine starter not starting JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual? Customer: not a gas hog starter not working JA: What is the model/year of your electr… read more
Eric
Eric
Retired
N/A
14,436 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x