Service AWD and check engine light

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Jun 2, 2009
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Wisconsin
2019 Highlander. I changed the oil today, cleaned engine and cabin air filters (both washable), cleaned mass airflow sensor and throttle body.

Now I get both check engine light and service AWD message. I think the AWD message first appeared when driving up on the ramps and they slid, but not 100% this is when. I don't think the check engine light was until I put the car "on" (engine not started) while oil was draining. At this point the MAF was not connected since I disconnected it to clean it. The air filters were removed later.

It drives fine but the messages still appear after several times stopping and starting the engine. I have the negative battery terminal disconnected right now hoping it clears things.

Other thoughts?
 
Why would you power on a vehicle when a sensor is disconnected?

Read the codes and clear if needed.
My thoughts exactly plus why is the key on when the oil is draining too? Not a normal nor good practice to do.
 
Why would you power on a vehicle when a sensor is disconnected?

Read the codes and clear if needed.
Was just trying to multi task. Not something I normally do, and only clean NAF and throttle body every 25 to 30k miles. I don't have a scan tool to clear the codes, thus disconnecting the battery. Is there a good basic one you recommend?
 
Was just trying to multi task. Not something I normally do, and only clean NAF and throttle body every 25 to 30k miles. I don't have a scan tool to clear the codes, thus disconnecting the battery. Is there a good basic one you recommend?
Disconnecting the battery rarely clears all codes. What is your budget?

Just for future reference, powering on a vehicle with connectors disconnected can cause some major issues. Sometimes things can even fry.
 
Disconnecting the battery rarely clears all codes. What is your budget?

Just for future reference, powering on a vehicle with connectors disconnected can cause some major issues. Sometimes things can even fry.
Cheaper the better, I wouldn't use it often.

It drives fine except for the dash lights/messages and I made an appt for next week at the dealership since it is still under warranty but would prefer to just clear the codes on my own (I think the CEL is not a problem and hope the same for the AWD message).
 
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It drives fine except for the dash lights/messages and I made an appt for next week at the dealership since it is still under warranty but would prefer to just clear the codes on my own (I think the CEL is not a problem and hope the same for the AWD message).
Theoretically, this will not be covered since it was caused by an outside influence.
 
Theoretically, this will not be covered since it was caused by an outside influence.
The AWD message wasn't. I just drove it on ramps. CEL was. Amazon has quite a few right now under $35 black Friday prices, I will get one if those for Saturday delivery, clear the codes, and hope they stay off (CEL should, at least).
 
Best and cheapest is to know what codes are there, then let the computer cycle out the codes, sometimes a few to several drive cycles and the lights should go out. The other AWD drive light was probably set as the system might suspend some operations to prevent damage. As you probably set the codes for the check engine, in your instance you could go to the car parts store and have the codes checked for free, and then if they haven't cycled out and only reflect being related to what was disconnected, you can continue normal activity and wouldn't need any battery disconnect. I am not sure how the 2019 Highlander computer program is supposed to run, so there may be variables from what I've suggested.

That said, 2012 Sedona, I disconnected the throttle body and forgot to connect it before starting the vehicle and now await it's cycling out of the system, but it actually seem to have helped diagnosis on other codes that weren't cycling out. I've thought it was a computer problem because mechanically the vehicle runs fine, and the check engine has cycled off a few times but as it also cycled on and I find the throttle body code along with the others. I think it may be holding the codes in memory and a dealer level scan tool might be what it takes to clear them. To be continued...

I got the Innova 5610 scan tool ($149 used) as suggested from another thread, seems to be same as Harbor Freight's Zurich ZR15S, video review at Harbor Freight link to see some of the function. Still awaiting shipment as the tracking shows it got sent back to the origin city on delivery day, so the new delivery is Saturday, I'm sure the shipper's are busy and I wish them all well.

I had an Innova 3160e $230, and the upgrade is $80 cheaper with a 15 day return is not as advertised via the pawn shop site. For ~$30 eBay has the Faslink m2 which is similar to the Bluedriver interface, I use it on a tablet being I don't have a mobile phone, seems to have similar function as my $230 Innova 3160, though I mainly use these for live data and misfire counts as I haven't learned much about other functions. Good luck.
 
If you drive the car a couple times I wonder if the MAF code will clear. It probably tripped the code because it was unplugged. Your other option is trying an auto parts store to read the codes and as the tech to clear them. Some employees won't, some will...

just my $0.02
 
Best and cheapest is to know what codes are there, then let the computer cycle out the codes, sometimes a few to several drive cycles and the lights should go out. The other AWD drive light was probably set as the system might suspend some operations to prevent damage. As you probably set the codes for the check engine, in your instance you could go to the car parts store and have the codes checked for free, and then if they haven't cycled out and only reflect being related to what was disconnected, you can continue normal activity and wouldn't need any battery disconnect. I am not sure how the 2019 Highlander computer program is supposed to run, so there may be variables from what I've suggested.

That said, 2012 Sedona, I disconnected the throttle body and forgot to connect it before starting the vehicle and now await it's cycling out of the system, but it actually seem to have helped diagnosis on other codes that weren't cycling out. I've thought it was a computer problem because mechanically the vehicle runs fine, and the check engine has cycled off a few times but as it also cycled on and I find the throttle body code along with the others. I think it may be holding the codes in memory and a dealer level scan tool might be what it takes to clear them. To be continued...

I got the Innova 5610 scan tool ($149 used) as suggested from another thread, seems to be same as Harbor Freight's Zurich ZR15S, video review at Harbor Freight link to see some of the function. Still awaiting shipment as the tracking shows it got sent back to the origin city on delivery day, so the new delivery is Saturday, I'm sure the shipper's are busy and I wish them all well.

I had an Innova 3160e $230, and the upgrade is $80 cheaper with a 15 day return is not as advertised via the pawn shop site. For ~$30 eBay has the Faslink m2 which is similar to the Bluedriver interface, I use it on a tablet being I don't have a mobile phone, seems to have similar function as my $230 Innova 3160, though I mainly use these for live data and misfire counts as I haven't learned much about other functions. Good luck.
I agree with Supersonic, there is a very high chance after clearing the "clear able" codes, "time" has a high chance of clearing the other code. I had some "permanent" codes thrown on my Hyundai and they disappeared to my scan tool after about a month and a half. They may be there, but they have been flashed out most likely from a different tune file.
 
Well, I hooked the battery back up and the AWD message is gone. The CEL was gone... but the car now won't start and the CEL is back, with a low brake power message. It pretends like it wants to start but dies quickly. Almost like a vacuum line is disconnected but all I did was hook the battery back up.

Stuff I have done on ten other vehicles causes so many problems with this one. I hate this car.
 
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The brake booster vacuum line connection is what I'd look for in my applications. I think that is the biggest but I'm not sure on a 2019 Highlander. As you probably went over the connections many times now, I'd suspect the idle relearn is the problem. On the 2005 Camry it took several restarts to get it to stay running and idle right as I recall, I didn't know what the issue was but I think it was either after cleaning the throttle body or a battery disconnect. There was a process but I can't seem to remember it or what I did wrong.

On a 1996 Camry, the idle stuck wide open when I first got it, that's when I learned about cleaning throttle body's. Your should be a 'drive by wire' meaning there isn't a cable from the accelerator, therefore as I understand the process of cleaning the throttle body, engine off and key on to use the gas pedal to open the throttle body for cleaning, as manually opening the throttle body might harm it. I have done it both ways and luckily have never had a problem.

You've got a really nice vehicle unless there is an anomaly just keep working with it and sometimes the learning curve can take lots of patients. The observation I am having with vehicles is the newer ones tend to be more complicating and delicate (as in lower cost manufacturing, smaller wires and fragile components) making them less practical and less affordable especially after warranties are expired. And from what I learned about warranties, it's minimum parts and labor until expired, then the up-sale for everything associated starts, but I've never had a car warranty so I may not be the authority on that.

"cleaned engine" I missed that detail, if using water it might need time to dry out. If it's below freezing try to get it into a garage and do what you can to circulate warm air. You may have a connection or component that is having an adverse reaction to the water or if it freezes it might be holding something up.
 
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I did a search online and this (AWD and low brake power messages) has happened to others when their battery was dead. I only had the negative disconnected last night, so thought there might have been some parasitic drain. So I checked the charge and it was low. After charging, it started and all seems fine (no CEL or warning messages). Hope it stays that way, as I only tried starting it once. Will still probably get a code reader.
 
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