Due to many obvious reasons, the past 20 months have brought us some interesting automotive problems. Many of them involve cars sitting much longer than usual.

Many customers who previously drove 20 miles to work round-trip five days a week in bumper-to-bumper traffic on Highway 101 are now only driving on local roads to drop off kids at school before returning to their home offices.

Last month, a customer called the shop to say that his 2013 BMW X5 would not start. The customer said he had jump-started the car to get it running. After doing that, he tried to shift into drive, but every time he tried to accelerate, the car instrument panel warned him that a door was open and put the car back into park.

Diagnosing the problem

The customer had the car towed to the shop and we got started. The first thing I asked the customer: How did he jump-start the car? He told me he gained access to the battery and jumped directly to the battery. I explained to him that jumping a BMW directly to the battery could cause damage in the electrical network.

When jumping any late-model car, one should always consult the owner’s manual first.

This BMW has jumper leads on the engine bay that make it quite easy to jump. Just make sure to never cross positive and negative.

I told the customer that the footwell module (FRM) may have been damaged before the battery died or perhaps when he jump-started the car. I suspected this because the customer could not put the car in drive. The FRM controls a lot of the body operations (lighting, windows, door, etc.). After further testing the car, we discovered the windows and the lights were not working. This looked like a classic FRM failure.

We connected the Intelligent Service Technical Application (ISTA/BMW factory tool) and scanned the entire car. We had several codes come up, mostly from the FRM. The FRM-related codes were for the door latches, lights and windows.

We also had a battery-exhausted code from the Intelligent Battery System. After running the scan, we went directly to the battery. Before even load-testing the battery, we could see it had a build date of 3312 (33rd week of 2012). The car had its original battery from the factory, so it was nine years old. The battery load test showed it had seven volts at 200 amps. The battery should have been at 10.5 volts at 350 amps. Of course, we had to replace the battery.

Replacing the battery

I have written several columns about how important it is to replace a BMW battery with one from the BMW factory. It is also important to follow the exact battery replacement procedure. Late-model BMWs use either a lead acid or AGM (gel) battery. The replacement has to be a like-for-like battery. For example, if the car has a 105-amp-hour AGM battery, it must be replaced with the exact one.

Problems occur when people assume all batteries are the same. We have cars come in all the time that are registered for a lead acid battery and have an aftermarket AGM battery installed.

In addition, BMW batteries must be registered to the car. The Intelligent Battery System needs to know how to control current to each module and to make sure the alternator is charging properly.

Back to our 2013 BMW X5. We first replaced the battery and registered it to the car. The next thing that happened was a bit of a relief: Everything worked. Now, you might think that is not that big of a surprise, but if I were to have 50 BMWs come in with battery and FRM problems, 99% of them would have to have the FRM replaced as well.

On this particular X5, the FRM and other control modules were shedding power trying to get the network to operate. Once the car was jumped, those same modules were shutting systems down trying to get the car to operate correctly, yet there was not enough amperage. Hence, the car could not be put into drive because the FRM was confused and thought the doors were open.

Since I started working on BMWs with FRMs, I have never seen one come back from the dead. Controller Area Network vehicles are extremely dependent on a properly functioning power supply.

The moral of this story is that if you get any type of battery warning on a late-model car, get it checked as soon as possible.

Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information, call 960-6988, email sfcsmv@gmail.com or visit sunnyvaleforeigncar.com.