Agreeing that batteries must be disconnected is not difficult to negotiate. With a little bit of research and some general understanding everyone can agree that it is necessary to disconnect the vehicle’s battery during most repairs. The hurdle that this article is going to discuss has nothing to do with the need for the battery disconnect but instead has everything to do with how it should be done and the dangers if its not done correctly. The best comparison is with computers. The proper way to shut down a computer is to follow the shutdown steps, through the operating system. This lets the computer shut down on its own. We’ve all pushed the button and forced a computer off or worse yet unplugged them. The reboot after that is time consuming and at times nerve racking. The computer goes through and performs self-checks, asks if it should open in safe mode, and then what feels like an eternity later finally opens up. Cars today are computers with wheels and they don’t want to have their power plug pulled. If it gets pulled there is going to be some repercussions or at least some steps to reboot them correctly.
- Honda states the importance of an occupant detection system reset after a battery disconnect and even a steering angle sensor relearn may be required after disconnecting the battery.
- Volkswagen says you must cycle the key and then perform a guided fault code finding by using a diagnostic tester.
- General Motors says you may have to program the volatile memory and on cars with stop/start it may not function until the car sits for 3 hours after programing.
- Toyota states that utilizing their Techstream to memorize steering angle sensor may be required and without doing so systems like lane departure, parking guidance, and pre-collision system will not operate. Power door locking systems may too need to be re-initialized.
- Nissan states you must reset electronic systems by utilizing a scan tool.
- Ford has in repair procedures for some of their vehicles that a battery monitoring system reset after installing a battery is required.
- BMW requires a battery registration process.
- Porsche requires fault codes be reset after a battery disconnect/reconnect.
- Chrysler company states you must check the PCM for any stored battery disconnect trouble codes and clear if required.
This short list covers majority of vehicles being produced today. It is possible to make the same statement for every vehicle manufacturer that is producing cars today. Of course, that list would be even longer. The point of the list is to show that it is quite possible that just disconnecting a battery will require some sort of calibration or code clearing.
In addition to the scanning it may be necessary to perform other acts to bring the vehicle to pre-disconnect condition. The simplest of these is to recalibrate the windows auto function. Manufactures that require that reset include Honda, Acura, Subaru, Nissan, Infiniti, Toyota, Lexus, Volkswagen, Audi, and GM. This list of course isn’t all-inclusive as there may be some that have been missed and others may require it on their new models. The point is from recalibrating steering angle sensors to resetting auto window functions disconnecting and reconnecting is not as simple as it once was. The only way to know what may be required is to consult the repair procedures, perform a scan, and ultimately a test drive and function test to insure all features work correctly.
|(Photo courtesy of Scot Manna) This is the electrical connection for a BMW Safety Battery Terminal, a pyrotechnic device that is designed to disconnect the battery in the event of an accident.|
When working with vehicles it is always possible a battery gets drained. Shops do not typically drive vehicles or leave them running for long periods of time so batteries never get an opportunity to get charged. Just like battery disconnecting/reconnecting, jump starting has gotten a bit more temperamental. Reconnecting a battery from a dead system wakes up the computers and the computers have a process to deal with it. A system with some charge is neither awake nor asleep. Hitting that system with more than 12 volts instantly can cause serious damage.
A quick example is a Porsche that required a $3200 repair from a jump start done wrong. The proper procedure states utilizing anything other than another vehicle to start a flat battery will cause damage to the computer systems. When using a jump box the small batteries in side may not be capable of handling the current draw from a starter, dropping below 12 volts and thus creating a spike of voltage when first connected and subsequent drop when the car is trying to start. The smaller jump boxes are utilizing lithium batteries which may have a fully charged voltage of upwards of 15 volts. Similar voltage is produced by a charger placed in start mode. In order to reduce the amperage load from the starter, charger and jump box manufactures increase the output voltage. This allows the starter to rely on voltage to accomplish its necessary wattage output instead of amps thus having less drain on the jump box or charger. The problem with this is the computer systems may not be equipped to handle the increased voltage. Most alternators are specifically regulated to no more than 13.5 volts and thus the computers are not designed to handle any more voltage.
With this Porsche failing to follow the proper jump start procedure created a hefty repair bill, delayed the completion of the vehicle, and created a CSI issue and lack of trust in the repairs. High end luxury automobile makers are not the only ones that have these requirements. Remember that most auto manufactures do not produce their own computer systems. There are a limited number of companies who produce modules, computers, and sensors for all the auto manufactures. This means that the same company producing electronics in a high end super car can be producing and likely are producing electronics in the cars that you see in your shop every day.
Proper safe repairs are critical. Shops and techs can not afford the liability of performing improper repairs. Insuring that proper repair procedures are followed is critical rather it is with something as in-depth as structural sectioning or with something as seemingly simple as a battery disconnect/jump start. The only way to insure the vehicle will leave the shop in as good of condition as it was in before the accident is to follow OEM repair procedures and guidelines!
Examples and data shared by Jake Rodenroth from asTech.