I'm a new member. Have an 06 4WD FEH with 5200 miles driven mainly by my wife. City milage recently dropped to 19-20 mph. I drove it for a couple days and discovered the brake regen doesn't always work, mainly during warmup.
2nd symptom - gas engine RPM is now erradic, sometimes suddenly jumping to 2600 RPM driving downhill in Drive, engine warmed up. And the battery isn't getting charged during the high RPM. Due to poor regeneration, we aren't always getting electric motor boost and the gas engine is working overtime to charge during warmup.
3rd symptom - coasting downhill in 2nd for better regen. works for about a block, then the gas engine RPM begins to dramitically increase. Watched it go to 5000 one day before returning to Drive. This all going down a steep two block residential street at 25 MPH.
4th symptom - Gas engine sometimes idles at 1600 in Park even though completely warm. No, it isn't charging the battery.

FEH is at the dealer today, but there are no error codes and their scratching their heads. Computer control has obviously lost it, but the techs. don't see it. Anyone out there experience anything similar?

 

"3rd symptom - coasting downhill in 2nd for better regen. works for about a block"

Do you mean Low mode? If you're in second, you are not in a hybrid.

 

If the HV battery temp exceeds "safe" temperatures, the FEH will not use the HV battery for power assist, or charge it via regen. One of the symptoms is a lack of power, and the ICE reving higher than normal.

There was a topic about transmission problems that talked about the engine reving and poor power at times. I believe it was due to the A/C not working properly, allowing the HV battery to get too hot.

Another cause of random engine reving is battery conditioning. Check out this thread on battery conditioning.

 

This SUV is very different than any other vehicle that you have ever driven. Look around the website and you will see that what your vehicle is doing is normal for a hybrid.

Your poor gas mileage is because the weather is cold and perhaps you are driving short trips.

You could possibly have a problem with your air conditioning and it is not cooling the battery (check other posts)

Do this, drive until the ICE is warm. Reset the gas mileage gauge. Drive around town for 15 to 20 miles. Check the gas mileage. It should be around 27 to 33 mpg.

Cold weather kills hybrid gas mileage. Especially on short trips.

Let us know how this turnes out.

Rick

 

ElectronBob:
Yes, I was referring to Low Mode.

 

Just to add to what has been said, the revving is most likely (unless you have a battery cooling issue as previously mentioned) because the battery is full and can't take any more charge. You'll find plenty of posts describing this behavior and the more technical reasons behind it.

 

Nash:
I read the threads you mentioned. Thanks for pointing them out. Good info.

Don't think high battery temp is the problem, because our weather is currently in the 0-40F range. I agree that low temp can greatly affect milage on short trips, but it's the combined symptoms of high erradic RPM and no brake regeneration that concern me.

The thread on Battery Conditioning could be related. But what I am experiencing, is that regeneration occurs normally during deceleration, but does not during braking. Thus I'm not obtaining all sources of regeneration that I'm supposed to. So I'm not sure this fits the battery conditioning scenario.

 

rxhybrid: Heard twice from the shop so far today, and they cannot find anything. Will be taking the mechanic for a drive myself later today so show him the symptoms. Hope to perform your little test while I have him in the vehicle.

 

emeraldbay, your 2nd and 3rd symtoms sounds normal. As randykato said, the RPM will rev very high to bleed off engergy if your battery is already full. This is esp noticeable during downhill coast on "L", and to a lesser extend on "D" since regen on "D" is less.

Do you have the NAV display to see the energy flow and battery diagrams?

I find that to get braking regen, I have to use the brakes lightly, and sooner (since I'm using the brakes ligthly). And the only way to know if it is regen is via the NAV hybrid screen energy flow. I almost always use "L" to slow down first to maximize the regen before using the brakes for regen.

There's a thread for TCH where HV battery charger/inverter was bad and deteriorating before the car actually stops functioning. That duration, his mileage was very poor.

Can you deplete the battery, and then go downhill in "L" to see whether symtom 2 occurs BEFORE the battery gets charged?

 

No, I don't have the NAV display. Bought the FEH off the showroom without that feature. You may be right about the battery being full. Will do some testing.

One other situation I didn't include in the original post happened this morning when I delivered the FEH to the dealer. Drove 15 minutes across town, vehicle was completely warmed up, but the ICU continued to run at 1600 RPM in park when I stopped at the dealership.

Will try to run down the battery, but the ICU hasn't been shutting down to do so. Will try double tapping the brake as others suggested to see if I can force it off. Hadn't heard that trick before today.