Maintenance Mode (engine constantly running)

Ryan Mechanic Wilmington, Delaware Posted   Latest   Edited  
Question
High Voltage - Hybrid & Electric Vehicles
Electrification
2012 Hyundai Sonata Hybrid 2.4L (4) 6-spd (A6MF2H)

I have to check transmission fluid levels with the engine running. I’ve tried a few different ways of putting the vehicle in “maintenance mode” which consists of pressing the brake and accelerator numerous times and shifting between park and neutral. All of the different combinations I’ve tried have not been successful and I’ve somewhat exhausted my resources so now here I am. I’ll try whatever you guys throw at me. Please help me.

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Matt Technician
Lawrence, Massachusetts
Matt Default
 

The "maintenance mode" procedure you described is a Toyota Hybrid procedure for keeping the engine running. A simple way to get the ICE to start is with the car in park and in Ready mode, press the accelerator pedal. To keep the engine running, turn on as many electrical loads as you can IE blower motor, high beams, rear defroster ect. The high electrical load should keep the ICE running long…

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Allan Owner
Sterling, Virginia
Allan Default
 

Often just turning the heat on full hot will do it on some hybrids

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Tim Curriculum Developer
San Diego, California
Tim Resolution
 

The current generation Sonata Hybrid has a Scan Tool command to keep the engine running. I can't promise it's there for your previous generation model, but I suspect it is. But it's probably not in the PCM menus, so check the HCU and other hybrid modules for the function.

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Ryan Mechanic
Wilmington, Delaware
Ryan Default
 

Yes, had success using a scan tool through the HCU Module. Thanks a lot Tim!

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Ty Technician
East Hartford, Connecticut
Ty Default
 

Yes a factory capable scan tool should have an option in HEV control system to force engine run. It just isn't needed in this case

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Paul Diagnostician
Rockland, Massachusetts
Paul Default
 

static​.​nhtsa​.​gov/odi/tsbs/2016…​.​pdf

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Helpful
Ty Technician
East Hartford, Connecticut
Ty Default
 

If the ICE is not running, the electric oil pump for the trans will kick in and supply the flow. There are no unusual methods needed to check fluid level.

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Tim Curriculum Developer
San Diego, California
Tim Default
 

That makes so much sense! I was wondering why it was to be checked ‘Ready’ with no mention of engine on or off. Now my head hurts a lot less. Thanks!

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Ty Technician
East Hartford, Connecticut
Ty Default
 

The car has to be in "READY" mode. It simply doesn't matter if the ICE is running or not. There will be fluid flow through the trans one way or the other.

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