Mercury 305 CID, Service Manual, Page: 625 / 967

90-823225--1 1096 5E-84 - ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY)
Audio Warning Buzzer Circuit Check
(1 of 2)
PPL
TO SYSTEM
RELAY TERM
“87”
TO BUZZER
TO IGN
TO AUDIO
WARNING
SWITCHES
TO TACH
J1-6
931 BRN
121 TAN
3 PNK
TAN/
BLU
BLU/
TAN
GRY
TO
IGN
COIL
D
C
B
A
PUR
121 WHT
TO BUZZER
(COOLANT OVERTEMP)
TO BUZZER
(AUDIO WARNING SWITCHES)
FROM AUDIO WARNING
SWITCHES
CIRCUIT DESCRIPTION:
The audio warning buzzer function of the ECM is
used to alert the operator of a critical engine function
parameter. Used in conjunction with the discrete in-
put circuitry, the ECM will supply ignition current to
activate the buzzer if a change of state is indicated by
any of the discrete inputs. When a discrete switch
changes state from normally open to closed, the
ECM interprets that an anomaly is present and will
complete the ground to the affected buzzer circuit,
energizing the buzzer.
TEST DESCRIPTION:
Number(s) below refer to circled number(s) on the
functional check chart.
1. This step performs a functional check of the
buzzer circuit.
2. This step identifies a short to ground in the control
circuit.
3. This step identifies an open in the control circuit.
4. This step identifies if the fault is a short in the har-
ness or a faulty ECM.
5. This step checks for an open in the circuitry from
the harness connector to the ignition fuse.
6. This step identifies if the open circuit is due to a
faulty ECM or warning buzzer circuitry.
DIAGNOSTIC AIDS:
An intermittent problem may be caused by a poor or
corroded connection, rubbed through wire connec-
tion, a wire that is broken inside the insulation, or a
corroded wire.
Any circuitry that is suspected as causing the inter-
mittent complaint should be thoroughly checked for
backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, poor
terminal-to-wiring connections, corroded terminals
and/or wiring, or physical damage to the wiring har-
ness.