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Rear motor not operating 45 min after charge!

1404 Views 28 Replies 9 Participants Last post by  wesleyorama
I am more than halfway into a 2,200 mile trip with a 5 month old 2023 I5, just passed the 5k mile mark. Beginning yesterday I noticed while on cruse control the car would lurch forward to compensate for being 2-3 mph under the cruse set point. Today I figured out the rear motor was no longer operating, the lurch was the delay until the front motor took over.

Today I charged 3 times for +/-30 min each. Then driving 70 mph for ~45 min all is normal car drives fine (no lurching). After 45 min of driving at 70 mph, the rear motor ceases to function, I then enable SNOW mode (constant AWD) to prevent lurching. (Image shows front motor doing all the work, rear shows a single bar but ODB2 reports zero)

Checked ODB2, no stored DTC's. The rear motor torque that was ranging between -8 & 35 during the 45 min after the charge, then torque is a constant zero.

Anybody know of a service bulletin that addresses this issue?
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I just checked the motor temp before driving this morning, it's reporting 72° which is 10° higher than ambient. I noted the motor temp at the time the rear motor quit yesterday, it was 212°. I did not see a significant reduction in that temp as I continued to drive. I'll watch it closer today.

Thanks for taking time to consider my issue and replying.

Sport mode will also keep both motors engaged. Almost sounds like the rear motor is over heating and it's limiting power to it, going around 70mph shouldn't be any issue for it. Or it may be a bad motor temp sensor giving false readings. I would use your obd2 app to monitor temperature and see if it's reporting anything funny and it will likely need to goto the dealer. Haven't heard of that happening before and no TSBs listed for the motor, just battery preconditioning and charging issues.
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The issue occurs 45-50 min after charging. I've been using EA chargers exclusively, and apparently they are limiting output to <150kW at thus time.

With regard to the torque the ODB2 reader I'm using does not appear to recognize the front drive motor (I'm open to recommendations for a better app), not sure about which motor temp the app is reading, but it was reporting 212° when the rear motor quit.

Thanks for reading & replying to my issue. We are all smarter together!

That's very, very interesting.

Do you happen to know what was the exact type of the fast chargers you have used? Were they 800V or 400V?

My theory is that if it was on 400V chargers (including Tesla Supercharger), it's possible that the rear motor or inverter overheated as it's actually the device that's converting from 400V to 800V at maximum capacity.

On the ODB2 reader, have you checked the drivetrain temperatures by any chance?
The motor temp is not what I expected. At my first stop to charge, I'd not traveled far enough to lose the rear motor, motor temp was under 200°, but during charging at around 100kW, the temp rose to over 200°. After driving only about 20 min, the rear motor quit with the temp at 215°. While continuing to cruse at 80 mph (Oklahoma hwy 44 speed limit), the motor temp continued to climb another 15°. Charging now at 150kW, motor temp up to 240°.
Here are some ODB2 readings captured while the rear motor is not working.
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When you experience this temperature on RWD propulsion unit stator temperature....
Are you pulling trailer
Are going over long incline for more than 10 miles
What is additional weight you have in the vehicle.
Was the battery management active for getting HV DC pack up to temperature
Driving with normal luggage & 2 ppl. No trailer, no excessive speed, 75mph 90% of the time.
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How long inclines you had when this started happening.....
What was percentage RWD vs using carscanner app before FWD was actively managing propulsion?
The RWD quits after about 45 min of driving at highway speeds. If I stop & charge for 30 min, RWD is restored, for about 45 min (sometimes less if the stop was shorter.)
I'm driving in normal mode until RWD quits (all seems normal at this point), then enable Snow mode (just to avoid the lurch, apparently caused by the car waiting for RWD for a second before enabling FWD).
Got it EOP Command Speed. 0 when stopped, ~1900 when RWD working & moving. I'll update when RWD quits.

Thanks for the suggestion!
This screen shows the Electric Oil Pump rear motor EOP Actual Speed 0 rpm.
You should bring up the EOP Commanded Speed, by clicking 2x on any other less relevant box (Batt Min etc.) and selecting [MCU] EOP Commanded Speed. Then you will see if the Electric Oil Pump works as expected.

View attachment 50005
Following is screen shot of EOP Command Speed after RWD quit.
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This screen shows the Electric Oil Pump rear motor EOP Actual Speed 0 rpm.
You should bring up the EOP Commanded Speed, by clicking 2x on any other less relevant box (Batt Min etc.) and selecting [MCU] EOP Commanded Speed. Then you will see if the Electric Oil Pump works as expected.

View attachment 50005
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The EOP Command shows between 2000-3000 (depending on how fast I'm traveling) both before and after RWD motor quits. The EOP Actial Speed always reports zero. Should I expect something different?

On the last screenshot the Electric Oil Pump (EOP) for cooling the rear motor shows 0 rpm, but it should be spinning at 3060 rpm (EOP commanded). Was the EOP spinning as commanded before the RWD quit?
Nice catch!!

Just verified with service tech that the rear EOP is not reporting any RPM's.

He is not familiar with the function of that item, and wonders why the RWD operates without the EOP for so long.

He is researching this issue now!

Thanks for the screen shot, that was helpful in advancing the troubleshooting.

Will update when more is known.

I checked mine today and rpm matched requested rpm. View attachment 50039
Hyundai tech support (on 3ed try) says: "replace rear junction box". Part is 2 days out. Will update then.

Thanks to all who have wrapped your minds around this conundrum!
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