1998 S-10-E Electric Truck
EV1 System 110 Inverter/Drive train


DTC-104 is described as auxiliary battery low voltage.

I recently noticed that my 12v auxiliary systems were not being supported
by the APCM and investigated.  When the auxiliary battery is at rest key-off
it should have nominal 12.x v level; vs, key-on the 12v systems should
increase to +/- the 14.2v level.  The DTC-104 diagnostic instructions lead me
to item 11, replace APCM.  With the unit obsolete that is not possible so I
removed the APCM and opened it up to investigate further.

The pictures below show the results; a burnt transformer leg which when
diagnosed lead back to a fauled Schottky Rectifier PN  203CMQ100.

After various testing as noted below the failed rectifier was determined to be
the root cause of the burnt transformer leg.  The transformer tested nominal
so the leg was repaired and the transformer put back in service.  The
rectifier was then replaced with NOS stock and the APCM put back in

DTC-104 then successfully cleared.

-- pictures to follow --
ACPM open
Note the burnt white
transformer leg.
Close up of the leg.
directly under the
main board under the
transformer.  This
picture is reversed
from the previous
shot to catch the PN.  
The transformer's
burnt leg is mounted
on the left side in this
picture where white
residue can be seen.
This is where the
rectifier failed.