Ford 2003 Mustang Workshop Manual page 3276

A1 CHECK THE BATTERY POWER SUPPLY TO THE INSTRUMENT
CLUSTER
CAUTION: Use the correct probe adapter(s) when making
measurements. Failure to use the correct probe adapter(s) may
damage the connector.
Key in OFF position.
Disconnect: Instrument Cluster C220b.
Measure voltage between the instrument cluster C220b pin 10,
circuit 729 (RD/WH), harness side and ground.
Is the voltage greater than 10 volts?
A2 CHECK THE RUN POWER SUPPLY TO THE INSTRUMENT
CLUSTER
Key in ON position.
Measure the voltage between the instrument cluster C220b pin 11,
circuit 489 (PK/BK), harness side and ground.
Is the voltage greater than 10 volts?
A3 CHECK THE RUN/START POWER SUPPLY TO THE INSTRUMENT
CLUSTER
Key in OFF position.
Disconnect: Instrument Cluster C220b.
Key in ON position.
Measure the voltage between the instrument cluster C220b pin 12,
circuit 20 (WH/LB), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A2 .
No
REPAIR the circuit.
TEST the system
for normal
operation.
Yes
GO to A3 .
No
REPAIR the circuit.
TEST the system
for normal
operation.
Yes
GO to A4 .
No
REPAIR the circuit.
TEST the system
for normal
operation.