MACS Monthly Newsletter - 2017 - SEP3

plain 'battery power loss' reset procedures. Some
scan tools and even a few standalone maintenance
reset tools have the ability. Obviously the radio's
clock will need to be reset. On many vehicles, the
radio's station presets may need to be re-entered as
well on radios that don't store favorite presets to
EEPROM / NVRAM (Electronically Erasable Read
Only Memory / Non Volatile Random Access Memory) within the radio or BCM.

Dave Hobbs

An easy method to record station presets prior to
a battery disconnect is to simply take your smart
phone and snap a few pics of the radio as you push
through the pages of station presets. When you're
through with your work and reconnect the old (or
new) battery, grab your phone and re-enter those
favorite stations. This may seem like a fairly laborious thing for what is potentially such a petty gripe
from a customer. We must remember that 100 percent elimination of gripes (big or small) is the goal
for any repair business. One very common ding on
dealer customer satisfaction surveys is the nuisance
of the customer having to reset the radio's clock and
station presets after picking their vehicle back up.

Figures 5 and 6: In cases where you want to keep battery power continuous
during repairs a 12-volt boost box can be connected to an OBD II DLC to 12volt acc. power plug adapter. Disconnecting a battery cable now will allow the
boost box to keep the memory power going. Now during service procedures
you'll have to remember to exercise caution when working around any circuits
that are normally hot at all times (alternator output, some blower modules,
etc.) as the boost box and DLC to 12-volt accessory power plug adapter are
now providing vehicle power regardless of whether the battery cables are connected or not.

Battery Power Loss Prevention Methods
I recall many years ago purchasing a gadget off
the tool truck called a memory saver, with a 12volt accessory plug (cigarette lighter) on one end
and a connection for a 9-volt battery on the other.
It worked great at keeping the radio's clock, station
presets and DTCs remembered IF I remembered to
NOT open the vehicle's door while the 12-volt battery was disconnected. The little transistor radio
9-volt battery would try in vain to supply power
to the dome lights before draining quickly and allowing the radio and other electronic modules to
experience power loss.

3. Connect adapter cable between the DLC
and the booster / jump box. Note: booster /
jump box must not have a safety feature that
shuts down its 12-volt output when a battery
is not connected in the system.
4. Remove negative battery cable end at battery.
5. Remember you are still working with a
live vehicle - power still present!

DLC Back Feed Method to Maintain Power to the Vehicle

Battery Cable End Method to Maintain Power to the Vehicle

Over the years techs have become more imaginative in using memory savers. Since many vehicles
power down the 12-volt accessory power receptacles with the ignition switch, most techs now are
utilizing a DLC adapter that plugs into the OBD II
connector 's ground and B+ terminals (pins 4 and
16). Any power through the vehicle has to come
into it via the fuse for the DLC's pin 16. That fuse is
typically 10 amps so it would then be the main fuse
for any accessory operation or short circuit which
might occur during any vehicle repairs. 10 amps
should be low enough to prevent any current (in
the event of a short circuit) to exceed the rating of
the wiring on the vehicle. This means high potential
for a major wiring short is very low and B+ memory power remains present at the vehicle's various
modules. This method is simple to do:

September 2017

Schumacher

1. Locate the shop's fully charged booster /
jump box. (Fig. 5)
2. Obtain a DLC to 12-volt adapter cable.
(Fig. 6)

Another method for keeping continuous B+ power to the vehicle is the use of a clean power supply such as those designed for maintaining vehicle
voltage while programming electronic modules.
The method to use one of these is simple:
1. Plug the battery charger / clean power
supply into a power receptacle.
2. Connect the battery charger / clean power supply to both battery cable ends. Make
sure the clamp connections for the charger /
maintainer / boost box are not in the way of
the battery cable end nuts / bolts that hold
the cable end to the battery post.
3. Remove negative battery cable. If battery
is to be replaced, remove positive cable as
well.

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017