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Hi,

I was driving home today and some warning lights came on saying there was a hybrid fault. I have just read the OBD fault code and it came up with 1 code P2797. I googled it and it says 'Auxillary Transmission Fluid Pump Performance'.

Has anyone had this fault or heard of it please?

I restarted the car and it drives in petrol mode only. The gearbox and engine seem to be running fine, just no hybrid function.

Any help is much appreciated.

Regards,

Hayne.

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I would check to make sure your 12v battery is fine. Probably worth disconnecting it for a minute or two to reset everything. If you still get the fault then it could be the hybrid oil pump or the oil pump controller is faulty, but maybe just low or dirty fluid. Probably needs a visit to a Lexus dealer to diagnose correctly, although how many dealers have actually seen this issue and can correctly diagnose the fault without just replacing expensive parts is another question.

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Colin,

Thank you for your fast response. I will disconnect the battery tomorrow and report back. I will check the fluid levels too.

It doesn't sound too common, but I found a thread where someone was quoted £3600+vat for a pump form Lexus !!!

That sounds ridiculous. If it is the pump, I have just had a quote for about £300 for a used one, and a thread tells me it is 3 to 4 hours labour to fit. Of course, I will diagnose before buying it, but I am very reluctant to use a dealer for diagnosis, as they are notorious for just replacing parts instead of carrying out a professional diagnosis, as you suggest (in my experience, main dealers are only useful if your car has warranty).

Still, the car drives perfect, it will just be higher on fuel consumption until I repair it.

Thanks again.

Regards,

Giles.

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Does anyone know where the auxiliary transmission pump is located and what it looks like?

Also, are there any wiring diagrams out there for the GS450h?

Thanks.

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you can get wiring diagrams / repair manuals legally from a couple of sources:

http://www.lexus-tech.eu

you pay for access on a time basis, as little as one hour for about £2.50. This is an official Lexus site and gives you access to European information.

https://www.alldatadiy.com

this provides access on a yearly basis, it isn't as complete and only has US manuals, but for what you currently need it for it the wiring diagrams as going to be essentially the same.

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That is great Colin. I will purchase an hours access and look up the info. I didn't realise this site existed.

Thanks again.

Giles.

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I've only just got round to checking some electrical stuff and have checked fuses and relays relating to the Hybrid system and Oil Pump, but I can't find the oil pump fuse.

It clearly states the location of this fuse in the left bank of fuses within the fuse box on the engine bay fuse box lid, but when I open it, there is no left hand bank of fuses where expected. There is a connector loom block which pulls out of the fuse box but still no fuses underneath.

All the other normal fuses are where expected and labelled accordingly on the right hand side of the fuse box.

Does anyone know how to locate it? Under the connector block, there looks like a silver colour bus bar under a clear plastic cover, but that doesn't look like fuses to me.

Any ideas?

any thanks.

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Hayne,

I have an '07 GS450h with 133k miles and the same P2797 code. Lexus diagnostics told me that the Oil Pump Controller Driver is malfunctioned (part# G1167-30021). They mentioned that the part either operates or cools the hybrid system. With it malfunctioning, I'm having the same symptoms as you driving without hybrid. The vehicle starts right up, but with "Check Hybrid System" and CEL Lights both on. I can drive fine for roughly 10-15min. After that, the vehicle goes into limp mode and a few additional lights pop up (VSC, etc.). The vehicle only allows me to drive a max of 50mph. If i keep going for another 5-10min, it limits me to 40mph. Each ~5min after that keeps going incrementally downward to a standstill. If i let the vehicle sit for awhile (1hr), it'll start right up fresh again.

Lexus quoted me $430 for the part. If you add labor, tax, and misc screws, it comes to a total of $1156. I can find the part online for $315. It looks like it is located under the hood on the passenger side. Reference part# G1167 below.

111666-955x659.gif

Have you had any luck fixing the issue?

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Hi Komain,

That's very interesting. It seems odd that the car is intelligently limiting and reducing your speed as you drive. That is a different fault to mine as my car comes up with the fault message and just drive perfectly normally, but without Hybrid.

I have heard that the pump controller can fail. Luckily for you, they are readily available from breakers yards, whereas the gearbox pumps are not easily available as pump removal means loss of transmission fluid, therefore an incomplete gearbox.

Im my opinion, I would buy a used pump controller and fit it yourself ( there is one on ebay uk for £150). at least if it doesn't solve your problem, you haven't spent $1200. I don't know if the controller needs coding to the car, but probably not. It also looks fairly easy to replace too, as you can see it in the engine compartment.

Very good luck with your repair. Please let me know how you get on. If it works, its a cheap fix!

I haven't had time to look at mine further yet, but I am going to my local garage on Thursday to buy some ramp time so I can continue my investigations. I'll keep you posted. It's hard finding time what with work and kids!

Giles.

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Thanks for the advice. I'm actually located in the US. But i looked up the part you mentioned on ebay and it looks like its for the 2013 gs450h. The part number is slightly different. So i'm not sure if it'll work with mine. I'll order at the below site for $350 shipped and take a crack at it.

http://www.lexuspartsnow.com/parts/lexus-controller-oil-pump~g1167-30021.html

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So I changed out the oil pump controller today and reset all the codes. It was pretty easy. Unfortunately it did not fix the problem. Any other ideas?

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Sorry to hear your fix didn't work. You would think that Lexus would have diagnosed this correctly, so not sure what went wrong there.

Well, at least you have done it yourself and at least you can try and sell your old pump controller and probably get most of your money back.

It sounds like your pump may be at fault. The fact that the car starts with the same fault message as mine, makes me think it could be the same thing.

I am still investigating the pump issue on my car. Last week I put it on a ramp to see if I could remove the pump motor. It looks very easy to remove the pump assembly (only three bolts), but the motor is fitted with bolts which are only removable when the pump assembly has been removed, but the ATF has to be drained first, otherwise it will spill out if removed.

So, as I need to drive the car daily, I drove it home with no work carried out. The next stage is to buy some transmission fluid (Toyota ATF-WS) and go back to the ramp. I will then drain the ATF, remove the pump assembly, connect the power wires to a 12 volt supply to see if the pump motor turns, check that the pump is connected to the motor shaft (i.e. not sheared off, or a worn spline). If the motor turns, then it is likely to be the pump position sensor (which could relate to a fault on the pump controller). If the motor doesn't turn (my preferred outcome), then I will remove the motor from the pump assembly, then refit the pump back to the car and refill with ATF, so I can still use the car.

Then, I will check out the motor to see if it has burnt out, or just has worn brushes. I will then send to a local guy who re-winds motors and see if he will tackle it.

Hopefully, the outcome may help you too.

Going back to your car, I have seen the VSC messages come up too. The first time was at pump failure. The only other time it does it is if I select 'Drive' before the READY light comes on. I take it you are waiting for the READY light to go steady before you put the car into drive? This takes about 10 seconds from pressing the power/start button.

Otherwise, may be you have 2 faults; the other relating to the VSC computer (stability control), which I think is related to the ABS, but not sure.

Another thing to try is to go onto JustAnswer and post a question to a seasoned Lexus Master Tech who may be able to help. I did this a couple of months ago and he gave me some diagrams and some good advice, giving me a way forward. I only cost me about £13. Worth a try.

Giles.

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REPAIRED FOR £7 !!!

Hi all,

I have finally repaired my transmission oil pump on my GS450h !!!

After many months of 'trying to find time' to repair it, I finally got the car on a ramp today.

Firstly drained the ATF fluid from the gearbox (approx. 4.5 litres came out). I them removed the exhaust bracket mounted on the gearbox (4 bolts). Then I unbolted the oil pump (4 bolts) from the gearbox and unclipped all the connectors from the oil pump controller and wiring mounts from the chassis and fed the cables back from the engine compartment to the gearbox area. I then checked out continuity of the wiring from the connectors to the pump. All were fine.

Next I removed the pump housing from the motor and inspected the shaft by trying to spin the shaft on the output of the motor. It was seized. I tried moving it with some mole grips and the shaft moved, but grated.

I then took the pump assembly apart to look for brushes (had to drill out 3x M5 screws as they were seized on), only to find that it is a brushless motor with 3 coils, like a stepper motor. I checked out the front shaft bearing and found that it was worn, causing the shaft magnets to grate against the motor coil assembly. Bingo.!!!!! Fault found!!!!

I then visited my local bearing specialist and, hey presto, he had the correct bearing in stock! I also purchased the rear bearing too, just as a matter of course, totalling £14 in parts. They are only little 22mm bearings, and are common parts.

Then I started to reassemble the motor with the new bearings. I had to drill out the 3 M5 screws completely and re-tap the threads to M6 and fit 3x new M6 screws in place.

I then reversed the removal procedure and then filled the gearbox with ATF.

I started the car. The same Hybrid fault came up. So I plugged in my code reader and cleared the P2797 code, and HET PRESTO. NEXT TIME IT WAS STARTED, THE CAR RAN PERFECTLY.

I now had full Hybrid functionality and a fully wrking car.

I am ecstatic. and extremely pleased with myself. Considering Lexus say the only remedy is a new oil pump at the cost of £3240. I have fixed it for £7.

All in all, it took me 5 hours to repair (not including finding a bearing supplier).

Lets hope this is good news for all of us GS450h and LS600 owners (same pump on both cars).

Regards,

Giles.

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Impressive. You just took DIY to a whole new level!

I am very pleased for you and hope your post will help others who encounter a similar problem.

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Great effort, thanks for sharing. Keen to keep my GS for some time yet but was concerned about this looming issue, a lot more confident about it now.

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You sir, are a legend! :yahoo:

Well done indeed! You should submit this as a how-to-guide and get a star for it!

In you face, Lexus dealer! :D

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Congratulations Giles and many thanks for sharing the successful outcome.

There will be a number of members who will gladly buy you the proverbial pint for your perseverance and willingness to share the result and the method.

Now if you can patent the process and lend it under licence to willing Indies, you look set to make a fortune and deservedly so!

I hope that news of this gets to Tony Richa as he had to "give his 450h away"

Regards and good luck.

John

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Thanks for all the comments and support. I hope it will be of help in the future. As Ganesh suggests, I shall write a 'how to' guide and post it in the next few weeks.

When inspecting the pump, it noticed it has been well designed for reliability and, in fact, the pump and motor are very simple and should last hundreds of thousands of miles due to its single moving part (the shaft with magnet assembly). As there are no brushes there is little to fail. Even the motor shaft position sensor is simple by design and easy to access once the motor has been disassembled. The sensor is an array of hall-effect switches (magnetic flux sensing) and is easy to rework. The 2 most likely failure points of this motor assembly (in my opinion) are the bearings and the output shaft seal.

The failed part is just a bearing, and bearings do wear, as we all know. There have been 4 revisions of this motor assembly since it was released in 2006 (my late 2007 model still being the 1st release) so Lexus have obviously known about failures and have made revisions to try and overcome this. I don't know what these revisions are, but I expect that the front shaft bearing was made larger/higher quality.

So, the point being that I don't see any real benefit of buying a new pump when the design is so mechanically sound (apart from the bearings!!!). If your pump fails, it is very likely to be this £7 bearing.

Giles.

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I should also mention what to look out for when your pump is due to fail.

These are my experiences;

About 2 months before my hybrid transmission oil pump failed, I particularly noticed a slow response when the gearbox changed the CVT torque multiplier ratio (i.e. equivalent to an overdrive gear).

About the torque multiplier: At about 55mph, the gearbox changes the ratio of the CVT to the high ratio (you will notice a short drop in power of about half a second) before continuing to accelerate. When decelerating below 35mph, the torque multiplier changes to the low ratio (again, you will notice a short drop in power/engine breaking, while this changes).

At this point, if the pump bearing is worn, the change is slower. This is most noticeable under hard acceleration, where the change can take a couple of seconds due to the pump motor struggling to turn properly, causing slower pumping of the transmission fluid (it is worth experiencing this now so you know what to look for in the future). I experienced a couple of times, the dash displayed the message 'Hybrid System Overheating' during hard acceleration. This too, was the pump failing to supply enough pressure to change the torque multiplier ratio in time. To try and overcome this just before my pump failed, I began taking my foot off the accelerator at around 55mph, just to give the pump a chance to supply enough to change ratio.

About 2 months later, while driving in electric only mode, the pump bearing seized and caused the car to grind to a halt, as there was no pressure.

If this does happen to your car, don't panic, just power the car off using the power button, then power on, wait for the READY light to go steady (takes about 10 seconds under the fault condition), then drive away as normal. The car will just be running in petrol engine only mode. The dash will show 'Hybrid System Fault'. The car will not drive at above 75mph. I drove my car with this fault for 5000 miles before I repaired it.

So, to summarise; if your car changes the torque multiplier ratio quickly under hard acceleration at about 55mph (could be up to 75mph, depending on acceleration), then the pump is functioning correctly. If you notice slow changes, or the overheating message, its worth replacing the bearing anyway.

I hope this will give GS450h owners a little more confidence as to the state of their pumps and what to look out for.

PLEASE NOTE; THIS IS JUST A SUMMARY OF MY EXPERIENCES AND MAY NOT APPLY IN THE SAME WAY TO YOUR CAR.

Giles.

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As far as I can recall there is no evidence of this fault being reported on 450h cars manufactured after 2007?

Regards

John

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Possibly not John but that may just be because of the age. In a year or two they may start failing as well.

If the 2008 model has a revised pump I doubt it was because of possible bearing failure, the GS450h would have been too new to have received reliability data from the sold vehicles in use.

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Possibly not John but that may just be because of the age. In a year or two they may start failing as well.

If the 2008 model has a revised pump I doubt it was because of possible bearing failure, the GS450h would have been too new to have received reliability data from the sold vehicles in use.

Valid points Colin. Thanks.

Regards

John

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Yes, very valid points Colin, but I would have thought that Lexus would have a fleet of long term test cars that would have many, many miles on them to test for early failures ( this is just an assumption) so it is possible that they picked this one up before customer's cars started to fail. I would have thought that all manufacturer's would do this to save on costs with recall management and reputation.

Still, if revisions weren't to do with bearing failure, I wonder what it could have been? I expect we will find out in due course.

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