I've been getting this on my 2006 FEH - no regen braking when the OAT is 25-35F. It happens after a cold start even with it garaged for the night. Eventually after driving 4-8 miles the regen braking starts to function again...this is 2-3 times as long as needed to warm up the engine and get EV mode.

When it happens, the batteries still recharge from the engine or L transmission setting so I don't think it's due to fully-charged batteries or battery temperature. It looks like a lot of you out there don't see this so I wonder what's going on?

 

It has everything to do with battery temperature.

When the battery is cold, it can take a slow charge, but not a fast one.

When braking, the regenerative brakes are about 20,000 to 25,000 watts.
A cold battery cannot accept this, so your hydraulic brakes do most, or all of the work.

However, the motor/generator can gently charge the battery, more in the 5000 watt range, when you are driving, or stopped at lights, etc.

After a few miles, the battery warms up, and the car behaves more like you are used to. I see this every day. Hope that clears up one mystery for you!
-John

 

I understand the outside/battery temperature and charging issue, but I'm still getting the brake warning light, ABS warning light, and "check brake system" message on some cold weather starts. It happened again this weekend, a few days after my Ford dealer service shop searched for, but was unable to find, any problem or current error code during a 70k service. Outside temperature was 17 degrees. The warnings came on and stayed on upon ignition start. After a minute, I turned the ignition off, waited briefly, then restarted, as was suggested here to reboot the vehicle computer. This time, all three warnings stayed on for about 10 seconds then went off. Hydraulic brakes appeared to function normally, though no regen braking due to the cold. This issue occurs only in cold weather at Lake Tahoe and never in warmer weather off the hill.

 

The ABS brake warning and the check brake system message should go out in around 3 seconds after start-up if the system is working properly. When you open the door or the dome light comes on, 12MM of brake fluid is pulled from the master cylinder to pressurize the brake system. After the system is shut down, in 4min the fluid is returned to the master cylinder.

Does anyone think the cold weather may be lowering the volume of brake fluid enough to activate a low brake fluid warning if it is close to needing fluid already? After the fluid is heated and expanded from the pressure pump and engine compartment, some fluid is then returned to the master cylinder to an exceptable level to turn off the warning lights. This would explain no codes and the check brake system and ABS warning lights going out. The manual does say that low fluid would cause a ABS warning. If you have an ABS deactivation, regen braking is also shut down.

Bottom line, try adding a little more brake fluid and post in the morning.

GaryG

 

I won't be up on the hill for another week or two. The vehicle is serviced at a sea level and warmer location. Brake fluid was checked at the 70k service, which came several days after the first incident and several days before the second. The warnings occur at 6500' in sub-freezing temperatures. Maybe lower temperature and pressure are causing a decrease in fluid volume?

 

Ogakor, going down a 6500' hill can wear the the pads which decreases brake fluid volume. If you have not changed the rear pads that wear twice as fast as the front due to regen braking, I would have them checked. Make sure the brake fluid is well above the min level also. At 70K, you have done twice the mileage as most of us. Someone may have checked your front brakes which normally wear faster, and didn't check the back brakes. Good luck, and I hope I've helped find your problem.

GaryG

 

Thanks for the suggestions. I am religious about maintaining vehicles with a good mechanic. In the case of my FEH, the 70k dealer service last week found all systems "good," including brake fluid, battery cold cranking amps, tire tread depth and tire wear pattern.

Actual brake measurements were:
Left front 7.80
Right front 7.60
Left rear 9.50
Right rear 8.80

The Ford multi-point inspection report card says "good" is "over 5mm or 7/32" (Disc) or Over 2mm or 3/32" (Drum.)"

I still suspect the brake master cyl. sensor, since that was the focus of the previously discussed service bulletin affecting my early production run '05. However, the service shop was unable to find a stored error code related to that issue.

This is my third winter in the FEH at the same Tahoe/coastal locations.

 

Have you replaced the rear brakes? If not, that information contradicts the workshop manual and the way my brakes are wearing. Also, there is no drum brakes, all four brakes are disc brakes. There is no cranking with the 12V battery either, so how would they give you a cold cranking amp reading? The standard Escape has a 590 Cold Cranking Amp (CCA) Battery, I guess they just take a reading from the 12V battery load tester. My FEH battery is rated at 500 CCA, but I know nothing about how they test that.

Let me quote section 206-00-2 of the '05 Workshop Manual Vol 2 regarging brake pad wear:

"Since the regenerative braking uses the electric motor to slow the vehicle's front wheels, front brake pad wear is reduced. The rear brake pads, because of the regenerative braking, wear at approximately twice the rate of the front brake pads."

Regen would stop or slow after the battery was full coming down a high elevation, so if you do this often, the front pads could wear faster than normal I would guess. You need to make that call.

It wouldn't hurt to add a little brake fluid past the min. level to rule that out though.

GaryG

 

Brakes have not been replaced. I'll check the fluid. Not only do I traverse a 7600' summit on the way to my weekend house, I also commute over an 1800' pass daily on the way to work. In addition, I do not pay much attention to mileage. So, I probably wear the brakes somewhat differently than others.

 

I also had the same problem last January in my '06 FEH. The dealer fix for it was to "Apply special grease to HPA connector on ACU and reprogram ABS module to latest calibration and perform air bleed ck". They also listed a "C1475 in ABS module" and referenced TSB 062201. I haven't had the problem since, but I also garage mine so I'm less likely to see it.