Sudden MPG drop on 2023 hybrid

[Btid3]

Hi all!

Long time reader, first time poster. I have a 2023 XLT hybrid thats been great for the last few years. 35000 miles so far.

But recently on a road trip I had an issue with the EV battery where a circuit was stuck closed and required the high voltage junction box to be replaced. I was in Canada and the Ford dealership up there was able to do the fix. Drove home (about 600 miles) with no issues.

Two weeks later, and my mpg has absolutely tanked. I usually get about 41-43 mpg per tank, and now I’m down to 29. The problem seems to be when the gas engine comes on. Looking at the instantaneous mpg, it still displays “electric” when driving in the city or coasting on the highway. But when the gas engine kicks in, the mpg drops to 7-10 when city driving, which is well below the 17+ it used to be.

My suspicion is that the electric motor isn’t contributing as much when the hybrid engine comes on, but that’s little more than a guess. No warning lights are on, so I don’t think it’s anything dire, just not running optimally.

Wanted to ask if anyone else has had a similar problem and what the eventual fix was? Planning on taking it to a dealership soon, but have no idea what I’d ask them to check.

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[Master Blaster]

Hi all!

Long time reader, first time poster. I have a 2023 XLT hybrid thats been great for the last few years. 35000 miles so far.

But recently on a road trip I had an issue with the EV battery where a circuit was stuck closed and required the high voltage junction box to be replaced. I was in Canada and the Ford dealership up there was able to do the fix. Drove home (about 600 miles) with no issues.

Two weeks later, and my mpg has absolutely tanked. I usually get about 41-43 mpg per tank, and now I’m down to 29. The problem seems to be when the gas engine comes on. Looking at the instantaneous mpg, it still displays “electric” when driving in the city or coasting on the highway. But when the gas engine kicks in, the mpg drops to 7-10 when city driving, which is well below the 17+ it used to be.

My suspicion is that the electric motor isn’t contributing as much when the hybrid engine comes on, but that’s little more than a guess. No warning lights are on, so I don’t think it’s anything dire, just not running optimally.

Wanted to ask if anyone else has had a similar problem and what the eventual fix was? Planning on taking it to a dealership soon, but have no idea what I’d ask them to check.

So what's different? Different fuel, temperature, pushing water, different load, stuck brake, time for plugs, different driver, different route, whatever.

 

[Mavster Mechanic]

A real time OBDII scanner would be helpful.

I have a ScanGauge III attached every drive. I learn what is normal so I can spot the abnormal.

 

[HeyBales]

During a whole lot of normal calm driving with the ICE on - there is not much in the way of Traction Motor horsepower used anyway.
Even during 20-30% power accelerations.
Unless you are just really kickin it into gear!

Wondering if they got a calibration wrong or missed one that should occur - since the whole HVB has to come out.
That would not be good if it had the SOC% off and thought it needed more of the ICE power for charge up to 40%.

Does it seem like the ICE is turning on more often, in places you'd not normally need it?
Or when it turns on seems about normal, truly just the MPG when it's on tanked?

At this point - a scan gauge on an untouched truck thru your normal driving route, compared to yours - would be about the only way to show something is off.

 

[Craiger9131]

I used to get the same, 42-43mpg. But all of a sudden it doesn't get above 40. Not a drastic drop but nothing else has changed on my end. I noticed after I had it in the shop for a service and recall. The recall was a towing issue. I don't tow anything.
I realize this is no help, just wanted to chime in. OR, maybe the mechanics are not familiar with the software.

 

[Craiger9131]

I used to get the same, 42-43mpg. But all of a sudden it doesn't get above 40. Not a drastic drop but nothing else has changed on my end. I noticed after I had it in the shop for a service and recall. The recall was a towing issue. I don't tow anything.
I realize this is no help, just wanted to chime in. OR, maybe the mechanics are not familiar with the software.

That happened to mine as well.

 

[Btid3]

So what's different? Different fuel, temperature, pushing water, different load, stuck brake, time for plugs, different driver, different route, whatever.

Unsure, no different fuel or driving conditions. I'm in the mid-Atlantic, so it's been warm and humid the last few weeks, but it's warm and humid every summer and I didn't have this issue for the last few years.

 

[Btid3]

A real time OBDII scanner would be helpful.

I have a ScanGauge III attached every drive. I learn what is normal so I can spot the abnormal.

This was super helpful. Ended up getting a scanner and have started tracking some metrics. it looks like the hybrid battery is fine (state of charge, power output, current are all normal). My MAF and O2 sensors aren't picking anything up, though.

as an update - check engine and red hybrid battery lights did come on briefly, but then went away upon vehicle restart. The OBD sensor didn't register any error codes. took it to ford, and they didnt find any, either. Gas mileage is still down, so no fix yet.

 

[Btid3]

I used to get the same, 42-43mpg. But all of a sudden it doesn't get above 40. Not a drastic drop but nothing else has changed on my end. I noticed after I had it in the shop for a service and recall. The recall was a towing issue. I don't tow anything.
I realize this is no help, just wanted to chime in. OR, maybe the mechanics are not familiar with the software.

Such a bummer. Would be really keen to hear what the issue is if you ever get it figured out!

 

[Btid3]

During a whole lot of normal calm driving with the ICE on - there is not much in the way of Traction Motor horsepower used anyway.
Even during 20-30% power accelerations.
Unless you are just really kickin it into gear!

Wondering if they got a calibration wrong or missed one that should occur - since the whole HVB has to come out.
That would not be good if it had the SOC% off and thought it needed more of the ICE power for charge up to 40%.

Does it seem like the ICE is turning on more often, in places you'd not normally need it?
Or when it turns on seems about normal, truly just the MPG when it's on tanked?

At this point - a scan gauge on an untouched truck thru your normal driving route, compared to yours - would be about the only way to show something is off.

I plugged in a scanner to see some of the metrics real time, and it looks like the HV battery is fine (at least according to my google searches). SOC stays between 35 and 45%, battery current is usually just a handful of amps, power doesnt really breach 20kw. I haven't really been able to test if the battery assist isn't helping as much as it should when the ICE comes on, though.

 

[HeyBales]

I plugged in a scanner to see some of the metrics real time, and it looks like the HV battery is fine (at least according to my google searches). SOC stays between 35 and 45%, battery current is usually just a handful of amps, power doesnt really breach 20kw. I haven't really been able to test if the battery assist isn't helping as much as it should when the ICE comes on, though.

If you still have the scanner - run in Sport or Tow mode - it attempts to keep it near 70%.
Of course - if calibrated wrong of course the system will show 70%, but doesn't mean the HVB really is there.

Also a good test - if coming off the highway on exit ramp without anyone behind you (because brake light won't be lit) - go into Low mode - should see upwards of 135 A charging, depending on what the voltage is at. At first, it'll lower as you slow.

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