How JustAnswer Works:

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

Ask Greg Your Own Question

Greg, Technician
Category: Lexus
Satisfied Customers: 6997
Experience:  Import tech
Type Your Lexus Question Here...
Greg is online now

Hello, I have a beautiful 2007 Lexus GS450h hybrid car,

Customer Question

I have a beautiful 2007 Lexus GS450h hybrid car, which is my pride and joy.
I was driving home last week and some warning lights came on saying there was a hybrid fault. The car just coasted to a halt with no power. It restarted fine and just says Check Hybrid System constantly on the dash. I got home and read the OBD fault code and it came up with 1 code which was P2797. I googled it and it says 'Auxillary Transmission Fluid Pump Performance'.
I restarted the car and it drives perfectly in petrol mode only. The gearbox and engine seem to be running fine, just no hybrid function. The only noticeable difference is that I am getting 25mpg instead of 33mpg, due to the Hybrid system not functioning.
From what I can see, the Axillary Transmission Pump is only required when the engine is not running (ie in hybrid mode) as there is no engine power to pump the transmission fluid round the torque converter, so it is done electrically using this pump.
Please correct me if I am wrong!
Is this a common fault and is it likely to be a faulty pump, fuse or something else??
Any advice is very welcome.
Submitted: 2 years ago.
Category: Lexus
Expert:  Shantal-Mod replied 2 years ago.
Hello Giles,
I'm Shantal and I'm a moderator for this topic.
We have been working with the Experts to try to help you with your question. Sometimes it may take a bit of time to find the right fit.
I was checking to see if you had already found your answer or if you still need assistance from one of the Experts.
Please let me know if you wish to continue waiting or if you would like for us to close your question?
Thank you,
Expert:  Greg replied 2 years ago.
Name is***** goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back,
This is normally the oil pump controller that needs replacing ,going from what you have said , sadly a very expensive part , This could cost you up to £3500.00.
The parts that could trip the P2797 code are :
The ECM.
Oil pump motor controller.
Hy transmission pump .
Wiring harness .
Have a good shop check this for you ,with this being a Hybrid i would use the dealer .
If you are lucky then you may just have a wiring issue.
Bur been known to happen after the car has done more than 120,000 miles .
If you still need further assistance then please don't rate, just get back to me with the reply button, and I will get back to you or inform another expert to assist.
Also there is no extra charge after accepting .
Kindest regards Greg
Greg, Technician
Category: Lexus
Satisfied Customers: 6997
Experience: Import tech
Greg and other Lexus Specialists are ready to help you
Customer: replied 2 years ago.

Hi Greg,

Thanks for your reply.

I will check this out. Please could you tell me where this transmission pump is located, so I can put it on a ramp and check the wiring (let's hope it is that).

Also, where is the ECM and oil pump motor controller located?

I can't understand why a controller would be £3500. That sounds crazy! If it is that, I will try to repair it (I'm an electronics engineer, so have a good chance!). Otherwise, it will have to be a non-hybrid car the rest of its life as they are only worth about £6000 in the UK used market, so that would almost right it off!

I look forward to the further info.

Best regards,


Expert:  Greg replied 2 years ago.

Hi Giles .

Customer: replied 2 years ago.

Hi Greg,

Thinks for all your help. The wiring info is great.

I will take a look at the car this weekend.

I will leave you a 5 star rating.

Best regards,


Expert:  Greg replied 2 years ago.
Thank you Giles .

Hope you only have a wiring issue all the best.

Rgds Greg

What Customers are Saying:

  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
< Previous | Next >
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
  • Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible. Charles
  • As a single woman, I really appreciate an excellent and affordable opinion.
    Thank you Geordie, I will not hesitate to contact justanswer in the future!
  • Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, do indeed know your stuff. Jim
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C.
  • 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!!!! Alex

Meet The Experts:

  • Greg



    Satisfied Customers:

    Automotive diagnostic tech
< Previous | Next >
  • Greg's Avatar



    Satisfied Customers:

    Automotive diagnostic tech
  • Matt's Avatar


    Mechanical Engineer

    Satisfied Customers:

    BEng hons Mech engineering, in auto industry 22 years
  • Ross's Avatar


    Diagnostic and repair technician

    Satisfied Customers:

    Licensed diagnostic and repair technician
  • Rob's Avatar


    ASE Certified Technician

    Satisfied Customers:

    30 years trade experience
  • uk_iaibal's Avatar


    UK Car Mechanic

    Satisfied Customers:

    Verified Car Mechanic.
  • Billy's Avatar


    Trainer/ Master Technician

    Satisfied Customers:

    Trainer 8+ years, master tech. 10+ years, SAE member