Battery Safety Terminal - BMW 5251 Service Manual

Battery, Starter, ~lternatorl
@
TO
fuse
& relay
panel
Battery Safety Terminal
A
Battery Safety Terminal (BST) controlled by the Multiple
Restraint System (MRS) control unit was introduced for mod-
el year 1998 vehicles. The system will disconnect electrical
power to the engine compartment
in
the event of a significant
impact. The MRS system fires an encapsulated pyrotechnic
device
in
the positive
(+)
battery terminal that disconnects
power to the engine compartment, but maintains power to
the exterior lights and interior of the vehicle.
point
002125~1
Table a. Battery, alternator and starter troubleshooting
1 -
/Starter motor or solenoid faulty. l ~ e s t starter.
Symptom
Engine does not crank
Engine cranks slowly or
not at all, solenoid clicits
when starter is operated.
I
I
Battery will not stay
IShort circuit draining battery. l ~ e s t for excessive current drain with everything
Probable cause
Fault in immobilizer system (EWS)
- C l e a n Battery cables loose, dirty or corroded.
Battery discharged.
Battery to body ground cable in trunk loose,
dirty or corroded
Poor connection at starter motor terminal 30.
Corrective action
Try another ignition key. If problem persists, contact
your authorized BMW dealer.
or replace cables. See 020 ~aintenance.
Charge battery and test. Replace if necessary.
inspect ground cable. Clean, tighten or replace if
necessary.
Checlc connections, test for voltage at starter. Test for
voltage at neutral safety or clutch interloclc switch.
charged more than a few
days.
I ~ a t t e r ~ faulty. /Test battery and replace if necessary.
Short driving trips and high electrical drain on
charging system does not allow battery to
recharge.
.
I
I
Battery cables loose, dirty or corroded.
Iclean or replace cables. See 020 Maintenance.
Evaluate driving style. Where possible, reduce
electrical consumption when malting short trips.
Drive belt@) loose, worn or damaged.
IAlternator or voltage regulator faulty. /Test alternator and voltage regulator.
Inspect or replace ribbed belt@). See 020
Maintenance.