As I write this, we just recently passed Halloween and the refrain from Bobby “Boris” Picket’s “Monster Mash” song has been playing on the radio, so I thought I would start out to that tune with some paraphrase. “I was working on my Expedition late one night when my eyes beheld an eerie sight. The message center on the dash announced that modules and systems were being shut down. My car was doing ‘The Load Shedding’ mash.”
Ahh yeah, I should just stick to my normal narrative.
The story is true — I was prepping for an upcoming class and I was working in my garage on my 2015 Expedition, gathering some scans and screen shots for that class. I had been working for about 20-30 minutes, KOEO, and pretty much had all the data I wanted for the class. I decided to hook up one more time just to be sure and plugged in my IDS and went to do another KOEO test. Instead of getting into KOEO the message center started announcing to me that various systems were being shut down, module after module appeared and said it was being shut down.
I clicked OK to each announcement and they finally stopped. I did a scan and had 15-20 U-codes. I was left scratching my head wondering what had happened? I had also been doing some electrical testing, so I had my voltmeter out and checked battery voltage and read 12.3V. As I thought about it, it occurred to me that perhaps there was a vehicle strategy that would reduce the load to keep sufficient charge in the battery to be able to start the vehicle. I pulled up the Ford Service Manual and sure enough began to read about load shedding.
I contacted a co-worker from my days with Ford, who still works there, and asked him some questions about it. He confirmed that Ford has used load shedding for at least the last five years and in some case longer. Here is what I learned:
• What load shedding is
• The correct way to connect a scan tool to a Ford
• The correct method of doing flashing and recalibration
• The correct method and tool to use to provide power to the vehicle when doing these tests
• Perhaps, most importantly, how to connect a power source to the vehicle
What is load shedding?
I have used only Fords in this article in terms of specific information about this system’s operation. I can assure you that other OEMs have load shedding in their vehicles. They will work in a very similar manner to what I describe with Ford.
This article will give you a good overview of how the system works on Fords and I am sure much the same way on other OEs. This article is not intended to take the place of you using the appropriate service publication to become informed about how these systems work and in particular the one that may be sitting in your stall.
The information about how these systems work, test procedures and what gets shed and when, may be found in Ford Service Information through the PTS website and other service publications. With that in mind let’s talk about what is going on with load shedding and energy management.
On late-model Fords (the earliest I’ve seen with this system is a 2013 Focus), Ford uses what they call a Smart Charge charging system that has the PCM controlling the alternator output. I should note that Ford as had the PCM controlling charging long before the 2013 model year. This system monitors multiple inputs and determines the best charging rate based on battery age, electrical load, ambient temperature, engine rpm and load shed strategy. Load shedding is controlled by the body control module and may be initiated by the PCM.
There are three running load shed states:
• Load shed 1 will be initiated if the alternator is at full load and the battery is discharging while driving with system voltage is below 11.5 volts. The BCM will start shutting off various accessories, like heated steering wheel or climate controlled seats. Depending on the vehicle and its options will determine what gets shut down at this point. They will be turned back on if and when system voltage returns to normal.
• Load shed 2 transient will occurs when system voltage is below 11 and the Electronic Power Assist Steering (EPAS) requires power. Systems that are shut down also will depend on how the vehicle is equipped.
• Load shed 2 continuous occurs when the transient condition last longer that 20 seconds. Again, systems turned off will be determined by how the vehicle is equipped. The Ford service manual will detail what accessories are turned off.
The engine off load shed occurs when the BCM determines that the battery state of charge is below 50 percent or the vehicle is in ACC or RUN without the engine running for 45 minutes. The first system to be shut off in this state is the audio/navigation system and there will be a message displayed that the system was shut down to preserve the battery.
Is there any way that I could have not had this happen that night in the garage? Glad you asked, as that brings us to the correct and critical way to work on and service batteries in these vehicles.
Load shedding falls under the operation of the electrical energy management system. This system monitors the battery’s state of charge, time in service, possible electrical circuit faults and of course the operation of the alternator. There is a sensor on the battery negative cable that sends the information about the battery and charging system to the BCM.
Proper connection of a scan tool
This sensor and load shedding is why it is critical to observe correct service procedures when doing any work on the electrical system or scanning, flashing, or recalibration of modules. Step one: when doing KOEO off testing or scanning you must connect a clean power source to the vehicle.
Connecting a scan tool is no different than any other — you plug it into the 16 pin DLC under the dash. What is recommended is that you also connect a clean power source to the vehicle before you really start testing. The exception to this? You’re doing testing on the starting/charging system or it is a quick scan and off to other work.
When you are going to be spending time doing testing that will require electrical power and may cause the system voltage to drop below 12.4V, you want to first connect a clean power source to battery positive and an engine or chassis ground. DO NOT connect to the battery negative terminal. Your charger must maintain the system at 13V or more while working on the vehicle.
I am not going to go into lot of detail about clean power sources other than a reminder that it is critical that you use chargers that are regulated to not exceed 14.5 volts. I have a Midtronics that I use. By clean I mean that in the process of turning the 110v AC of the wall outlet into 12-14V DC that the AC current and voltage variation is removed.
I was at a used car store over the weekend helping my niece look at and find a vehicle to purchase. The vehicle we were looking at seemed to have a dead battery. The jump box the salesman used was dead, so the tech who worked there pulled out an extension cord and the shop charger. It was one of those big ones. I couldn’t help but notice the wires were frayed and covered with black tape right at the clamps, you know what I’m talking about— rather than purchase new clamps and properly repair the wires we tape up the fray and hope for the best. I can only imagine what the quality of power was to that car.
Another side comment that is related to this topic. How many of you work on used cars at a dealer? You’ve seen the Uxxxx codes indicating low battery voltage as the car’s battery goes dead while sitting on the lot. You’ve also seen a lot of overcharge Uxxxx codes by battery chargers put on high and having the system voltage exceed the threshold for setting that code by going well over 14.5V.
Correctly connecting a power source
To connect power from an outside source to any of these vehicles requires that you connect the hot lead to battery positive. The ground lead is connected to a good underhood ground.
Jump starting a vehicle with this system also requires that you do not attach the jumper cable to the negative battery post or connection.
What happens when you don’t follow this protocol? You confuse the battery state of charge calibration and monitoring. The load shedding may not work correctly until the system has a chance to recalibrate itself.
The good news is that the system will reset itself, on its own, after the vehicle has set for at least 8-9 hours in sleep mode. I had to do that with my Expedition because although I did have a clean power charger, I had hooked it up to battery negative. I had not read the service manual to know that connecting to a body or engine ground was needed. I didn’t know anything about the system and how it worked.
Correct procedure for doing calibration or flashing
This is even more important when doing calibrations or flashing. If system voltage drops too far during that time, you don’t need the BCM going into load shed! As with scanning and other testing, step one in calibrating or flashing is to connect a clean power source to the vehicle.
Electrical energy management system
As you might expect, the features of this system and how it deals with correct and incorrect connection outside power sources to the vehicle vary from one model of Ford to the next. Battery condition monitoring, load shedding all generically work the same but as you might expect will react differently on a Platinum Edition Expedition than on a base Focus.
This system is also responsible for keeping the battery charged. It varies the charge rate based on things like battery condition and age, ambient temperature, and accessory demand. What gets very interesting is watching the PID that is monitoring current flow to and from the battery. There are times when the battery is actually providing some of the operating power requirements and other times when it is being charged and other times the alternator is providing all of the system’s needs.
The reason this is done is twofold; well, actually it’s one reason with two benefits. This is done to improve overall fuel economy. Improving overall fuel economy also lowers emissions.
As I noted above, one of the features of the electrical energy management system is that it monitors battery state of charge, time in service, and therefore battery life. One of the options you may run across on your scan tool, particularly the IDS is the option to recalibrate the battery monitoring system. It would be a natural thought to consider doing this if you’ve connected a battery charger or jump box incorrectly. Let’s do it now rather than wait for the system to do it over the course of 8-9 hours. DON’T do it.
Battery replacement is when you use the scan tool to do the recalibration. This resets the learned battery data, the in-service time counter and lets the system know there is a new battery in the vehicle. Yes, you must have a scan tool to do this; there is no other way to do it.
Failing to do this reset after installing a new battery may cause unwarranted operation of load shedding and may limit the electrical energy management system functions.
Baseline electrical testing
Before I close out this piece let me do another quick reminder of checks that you should be doing whenever you’re servicing the vehicle’s electrical system. It never hurts to be reminded of those checks we all know we should do, and sometimes, we forget to do them.
First, checking starter current draw and voltage during cranking is a good practice, particularly for finding intermittent hard starts. I’ve run across more than one vehicle that “sounded” as if the starter was turning fast enough that the battery would not be a concern, yet a test of cranking voltage showed it under 10V. Cranking speed was really too low and when system voltage gets around 10V or less the vehicles control modules may go back to sleep.
Another critical test on the charging system is AC voltage. As you know the alternator (actually, “alternator” was a Chrysler brand name — it is an internally rectified AC generator) creates AC current and there are diodes within the component that rectify that output into DC current. Some AC does manage to get by the diodes — too much and strange things begin to happen, including decreasing the life of the battery.
The specs on this test are readings that are below 0.5VAC with the rpm at 1500+ and at least 20A output by the generator. In excess of 0.5V replace the generator.
Conclusion
The good news in learning about load shedding is that even if you have made incorrect connections when charging or jump starting a vehicle equipped with it, you probably haven’t created any real concerns for the owner. The OEs have been telling us for years that we should only ever connect to battery positive and a good body or engine ground. Now, there is good reason for that beyond just safety.
Last, don’t forget to check if the car you’re working on needs to have a scan-tool reset as part of installing a new battery. When you get a customer in who’s done their own replacement or gone to a parts or big-box store and gotten a battery you might want to consider looking to see if this reset was done for them.
I’ve still seen load shedding occur a couple of times since that night, only because I didn’t take the time to put the charger on before doing KOEO activities. Those old habits of “I’m just doing a quick check and don’t need the power source,” are hard to break.
