Ford 2003 Mustang Workshop Manual page 3655

Is the resistance less than 5 ohms?
PINPOINT TEST C: A SINGLE MIRROR DOES NOT FUNCTION WITH
SWITCH LOGIC
C1 CHECK THE EXTERIOR REAR VIEW MIRROR LOGIC
Disconnect: Exterior Rear View MirrorC516 (Driver), or
C622 (Passenger).
Disconnect the suspect exterior rear view mirror C516
driver or C622 passenger.
Measure for voltage or resistance at the suspect exterior
rear view mirror harness side, while actuating the
exterior rear view mirror control according to the
following chart.
Exterior rear view
mirror control
Circuit
540
(RD)
540
(RD)
541
(DB)
541
(DB)
542
(YE)
542
(YE)
542
(YE)
542
(YE)
Exterior rear view
mirror control
Test Step
Measure for
voltage or
position resistance
Driver
Left Greater than 10 volts
Right Less than 5 ohms
Up Greater than 10 volts
Down Less than 5 ohms
Left Less than 5 ohms
Right Greater than 10 volts
Up Less than 5 ohms
Down Greater than 10 volts
Measure for
voltage or
operation.
No
REPAIR the circuit.
TEST the system for
normal operation.
Result / Action to Take
Yes
INSTALL a new exterior rear
view mirror motor. REFER to
Mirror—Motor in this section.
TEST the system for normal
operation.
No
GO to C2 .