I believe I am the first one to post such message on a 2013 GS 450h. Lucky me. Car has 75k miles on it, so yes not driven that far, especially in past five years that I have owned it. I have googled some possible reasons, and one is to charge up the 12V battery. The other is to disconnect the 12V battery for 10 minutes. 12V battery is new since 2021, so just over three years old. Was about 1 mile into a trip last night, and the message popped up. Was able to drive it back home ok, but it seemed the Hybrid system disengaged as there was no graphics present indicating an engine running to charge the battery and the flow of such energy. Last resort is to get it towed to a Lexus dealer 45 miles away. Figured that is last resort, but wanted to try some troubleshooting on my own.

Thanks all!

 

Before you do anything, check the actual codes (DTCs), as these cars scream "check everything" for every single reason imaginable. And no, you're not the first - perhaps here, but not overall. Therefore, don't worry.

 

@Hues10 - It would be nice to actually see the exact message you saw, but I presume it is like the image below for (USA). If so (as noted in the image below), the message does not necessarily indicate a possible malfunction in the hybrid system. Instead, it may indicate a malfunction in one of the following systems: the electronic engine control or the electronic throttle control or the transmission control.

I don't know if disconnecting the 12 volt battery for 10 minutes would reset anything - or what it would actually reveal was the problem - something I feel sure you're wanting to know.

I would consider driving the car to the Lexus dealership's service department 45 miles away (since you were able to drive it home from your interrupted trip). Worse case would be having it towed in from a point midway from home to the dealership versus the full distance from your home.

My wild guess is that; it has nothing directly to do specifically with the hybrid system (including the traction battery or the 12 volt battery), but whatever it amiss caused it to drop the hybrid charge information/flow graphic.

When you find out what caused this 'check' warning message, please let us know...

 

BCLexus. Always a wealth of knowledge. I just ordered a scanner tool to get some more information. Coming Friday from Amazon, so hopefully, I can have additional details posted on Saturday. I still want to charge the 12V battery first, just to make sure that would have nothing to do with it. It was just weird to get this message one mile into driving it, and then it went into limp mode it seemed with the engine running, but no graphics of the engine doing anything. I babied it home, even turning off the AC. Been a really reliable and good car. I usually can do normal maintenance stuff on a car, like fluids, brakes, filters, even shocks. But Hybrid system check. Out of my league.

 

Did the low speed throttle response change?

 

I want to say yes, as it seemed the engine did not shut off. Case in point, to get to my house, one does a 3/4 mile one way loop at 25 mph. The car usually does this in EV mode only. The other night, it seemed that the engine remained running, but I wasn’t pushing it. Since the hybrid graphics were shut off, I couldn’t see anything happening. That was part of my original question, does anyone know how far the car drives in engine mode only. I read online, that once the hybrid battery is fully discharged (to the 20% level), the car would shut off. Did not know if that is true or not, as I don’t think anyone has tested it. Stay tuned. I will update when I know more.

 

@Hues10 - Here's a offhand possibility - when the 12 volt battery was replaced in 2021 the heat sensor embedded in the original Panasonic 12 volt battery was not [either] replaced or reconnected. Going on this 'offhand possibility', without the heat sensor connected the 12 volt battery was not allowed to be charged by the AC/DC converter since the time it was replaced - and since the 12 volt battery is responsible for powering the electronics in the car - the 12 volt battery finally became depleted one mile into your recent trip. This is just a possibility or my WAG (in the case WAG does not stand for wives and girlfriends!)...

 

I am hoping that for some reason my problem is related to the 12V battery. I just moved a month ago, and still haven’t gone through all the boxes, so have not located the battery tender charger. That is my mission today. Have been driving short trips lately the past two weeks or so. Keeping fingers crossed that magically I find the battery charger, and it magically makes my problem go away.

 

This is all quite interesting.

If ("if') the 12 volt battery is practically depleted due to it not having been kept charged by the car's AC/DC converter, then it wouldn't have the ability to power up the car's electronics - such as the radio and maybe not the navigation system. Yet, it appears from what you're saying those electronics are still working normally.

I would be interested in knowing how your 12 volt battery would test out being load tested.

My 12 volt battery is the original from when it was installed in August, 2018. I had it load tested (like a typical vehicle cranking battery) in December, 2021 when it was 6 years-old and after the car had set undriven for over a year (with the exception of me diving the car less than 10 miles to the dealership) with the following results:

 

The car physically can't drive in "engine mode only". What happens in the "bad battery" limp mode is that energy flow from and to the battery is severely restricted - you'll practically get no torque fill whatsoever. You would've immediately noticed this. The car will attempt to "maintain" the battery charge in a certain range and will only ever discharge it on initial startup in order to crank the engine. No regen, no fast force charging, no torque fill (well, ever so slight, as the way the transmission works kind of requires it - but for all intents and purposes - none).

Read the codes. A good bluetooth dongle with, say, torque, will do the job - and there's always apps like dr. prius (which the GSh incidentally is - albeit RWD and with a v6).

If there's no (noticeable) loss in "snappiness" of the throttle pedal, it's unlikely that it's the battery at fault.

p.s. re: "normal maintenance stuff" - the brakes & brake fluid on this car require specific knowledge re: how to service brakes on Toyota hybrids and/or ECB-equipped cars (TLCs, GS460, LS460, some others). It can be done without techstream on a lot of models, assuming that you know the proper "rituals", but don't skimp on educating yourself. These cars can and will eject pistons for "self-testing" unless they're in the proper state - amongst other possible issues.

 

Check Hybrid System

Uh oh. Does your hybrid have a check hybrid system message on the dashboard? What does check hybrid system mean?

Many times, customers are upset when they call in to report this warning message. They’re assuming that the hybrid battery has failed, and that’s possible, but it’s not a foregone conclusion.

Here’s the good news. Just because the hybrid system warning light came on, it doesn’t necessarily mean you’ll need an expensive repair.

Sure, it might be a hybrid battery pack or inverter, but it might not, so don’t worry prematurely. There are many inexpensive issues that can cause the warning. There are even a few things you can fix yourself.


So, what causes the check hybrid system warning message?

Most of the time the message indicates that the hybrid computer has found a problem with the hybrid system.

This system includes the transaxle (with electric motors), inverter, and hybrid battery. However, it doesn’t mean that any of those components have failed.

For instance, something as simple as a towel draped over the rear seat might cause the error message. There is a battery cooling inlet near the back seat. If it becomes blocked, it can cause the warning light. Maybe the traction battery's cooling blower/fan or inlet filter or its ductwork needs cleaning.

It’s also possible that one of the hybrid system’s dependencies has a problem, like the internal combustion engine or ABS system. When this causes the message, it’s known as a “sympathy code” or “collateral code”.


Do you need to stop driving if the check hybrid system messages appears?

Let’s say a check hybrid system warning message appears. If you plan to keep driving, the most important thing is to look for other lights and indicators and to pay attention to any other issues with the way the car is driving.

For instance, if you also see that your car is overheating - stop driving right away and call a tow truck. The same goes for the low oil pressure light.

An example: Let’s say you own a 2009 Toyota Highlander Hybrid, and the check hybrid system warning message appears. The car seems to be driving fine so you continue driving it. When it gets to the service department P0AA6 caused by a water leak. The car hasn’t been hurt at all. It was fine to keep driving it.

The Check Hybrid System warning message may be accompanied by symptoms such as:

Reduced speed and acceleration.
Hybrid system not working and the car running solely on petrol.
Decreased fuel economy.
Car going into limp mode.


How to reset check hybrid system message.

Unfortunately, the warning shouldn’t really be reset. To be clear, you can reset the check hybrid system warning, but you shouldn’t.

So why not reset it? Here’s the main reason:

When the check hybrid system alert appears, diagnostic data is stored in the control unit. This data is what we use to diagnose the problem with your car.

If you erase it, we’ll need to recreate the problem before we can start to find out why the warning appeared.

However, there are some valid reasons to reset the check hybrid system warning. Some codes, like loss of isolation codes, will prevent the car from restarting. If you need to move the car out of a parking garage or something, it might make sense to clear the trouble codes.

► So, how do you reset it? There are two ways.

Either use a scan tool to clear the diagnostic data, pull the backup power fuse for the ECU, or simply disconnect the 12V battery and wait a while before reconnecting it.

 

@Hues10 - I recommend finding out what DTC code is displayed to give you a heads-up on why the Check Hybrid System message appeared. At least by knowing the DTC code you might be better prepared deal with the remedy. Most any auto parts store can read the DTC codes at no charge, or buying a reader is not very expensive...


Common hybrid fault codes and what they mean

When you plug a diagnostic device into your car’s OBD2 port, it may display one or more of the following fault code. Here is an explanation of what each one means:

P0A80: This is a common code that indicates a problem with the hybrid battery pack. It could be caused by a failed battery cell, a damaged battery module, or a problem with the battery management system.

P0A7F: This code indicates a problem with the battery pack’s state of charge (SOC) sensor. The SOC sensor measures the amount of charge in the battery pack and sends this information to the vehicle’s computer. A malfunctioning SOC sensor can cause the hybrid system to operate inefficiently.

P0A92: This code indicates a problem with the DC-DC converter, which converts high voltage DC power from the hybrid battery pack to lower voltage DC power for use by the vehicle’s electronics. A faulty DC-DC converter can cause the hybrid system to operate poorly or not at all.

P0AA6: This code indicates a problem with the electric motor temperature sensor. The electric motor temperature sensor measures the temperature of the electric motor and sends this information to the vehicle’s computer. A malfunctioning temperature sensor can cause the hybrid system to operate inefficiently.

P0AC4: This code indicates a problem with the hybrid powertrain control module (PCM), which controls the operation of the hybrid system. A faulty PCM can cause the hybrid system to operate poorly or not at all.

 

► LEXUS HYBRID CONTROL SYSTEM > DIAGNOSTIC TROUBLE CODE CHART

Also, in above linked chart you can:
Click on the green 'NEW" button and then 'Engine/Hybrid System' in the left panel and
Look under 'Contents' for the: DIAGNOSTIC TROUBLE CODE CHART

 

As I have always said, BCLexus and others here are a wealth of knowledge. So here is the update. I found the battery charger last night, but it was raining too much so I did not try to hook it up. Just this morning, I checked the 12V with a voltmeter, it ready 12.19, so low as I suspected. The charger is on it now. The bad news is that the scanner is now not being delivered until Sunday from Amazon. Price you pay I guess for moving away from the big city. So my question is, once the 12V is charged, do I start the car and test drive it if the message goes away? If the message doesn't go away, do I leave it running for like five minutes then just wait for Sunday? Just trying to game plan here as I have not tried to start it since Tuesday night. I did check under the hood, the coolant levels are fine and very pink. No visible rodent chewing wires issues. Thanks all for your input and advice. I have not seen anyone with this issue for this generation. I hate being the guinea pig.

 

I don't know what the threshold is but the 12.19 volt reading for the 12 volt battery is really not overly low at all - and keep in mind the 12 volt battery is responsible for powering the onboard electronics like the radio and NAV. The traction battery starts the V6 engine via the hybrid motor.

What is the nearest auto parts store that can read DTCs for you? Maybe you can buy a scanner there, or maybe you have another store that sells a scanner nearby you.

I would start the car and see if you have the Check Hybrid message - and see if you have the hybrid graphics displayed. I would desperately want to know what DTC had been thrown because that will lead to what the problem was/is. So, even if the message is still displayed and even if the hybrid graphics are not displayed I would consider driving the car a short distance around your neighborhood to try to determine if the car is in limp mode - or if the car has both the ICE and the EV power like normal - or if the car gives you any feel or indication it is operating differently from being normal. If the car otherwise reacted normally I drive it to an auto parts store and learn what DTC their scanner displayed. That is what I would do...

Keep in mind the Check Hybrid message may have nothing to do with the proper operation of the hybrid system. For example, the message may have been triggered by a thermistor failure or clogged cooling blower/fan which in turn may be responsible for dropping the graphics as designed in the parameters of an ECU.

Of course, the DTC is going to be important in determining what the issue was/is and where to begin looking to correct the issue.