Instrument Cluster
Refer to Wiring Diagrams Cell
60
, Instrument Cluster for schematic and connector information.
Principles of Operation
Tachometer
Engine RPM information is relayed to the instrument cluster (10849) (also referred to as the hybrid electronic instrument cluster [HEC]) from the powertrain control module (PCM)
(12A650) via the SCP network.
LOW FUEL Level Indicator
The low fuel level indicator is hardwired from the fuel sender to the instrument cluster. The instrument cluster will illuminate the low fuel indicator when the usable fuel quantity is less
than 1/8 tank (15%) of fuel tank capacity.
Speedometer Gauge
The instrument cluster receives the vehicle speed signal from PCM over the SCP network and displays it on the speedometer gauge. If the instrument cluster receives no vehicle speed
signal after one second, the speedometer defaults to 0.0 km/h (0.0 mph).
Fuel Gauge
The fuel sender is hardwired to the fuel gauge. When the instrument cluster fails to receive the fuel level signal for more than 33 seconds, the fuel level gauge will move below E
(empty). If the fuel level signal operates correctly for more than 33 seconds, the fuel gauge will return to the correct position.
Fuel fills of less than 9.5 liters (2.5 gallons) require at least 10 minutes to update the fuel gauge indication.
Engine Coolant Temperature Gauge
Engine coolant temperature information is received by the instrument cluster from the PCM over the SCP network. Engine coolant temperatures above 121°C (250°F) will cause the
gauge to indicate above the normal band. If the engine coolant temperature information is missing or invalid for five seconds, the temperature gauge will indicate below the cold (C)
position.
Voltage gauge
The voltage gauge displays the system voltage as measured at the instrument cluster run input.
Low Engine Coolant Indicator
The low engine coolant indicator is hardwired from the low engine coolant switch to the instrument cluster. When low engine coolant is detected, the low engine coolant switch will close,
thus grounding the low engine coolant switch input to the instrument cluster and causing the low engine coolant indicator to illuminate.
Refilling the engine coolant will cause the low engine coolant switch to open and the indicator to turn off at the initiation of the next ignition switch cycle.
Odometer
The instrument cluster receives odometer message from the PCM and stores the mileage in memory. When the instrument cluster fails to receive the odometer message for more than
two seconds, the odometer will display dashes.
Oil Pressure Gauge
The oil pressure gauge is hardwired from the oil pressure switch to the instrument cluster. The oil pressure gauge will indicate either normal or no oil pressure.
BRAKE Warning Indicator
The BRAKE warning indicator activates when the generic electronic module (GEM) detects the ignition switch circuits are in the RUN state, when the GEM detects low brake fluid level
or that the parking brake is applied, from the brake input circuit. The BRAKE warning indicator will prove out starting when the GEM detects the ignition circuits make a transition to RUN
or START from OFF, ACC, or keyout and ending when either three seconds have elapsed or when the GEM detects the ignition circuits make a transition to OFF, ACC, or keyout.
Safety Belt Warning Indicator
The seat belt switch is hardwired to the GEM. The safety belt warning indicator will be illuminated when the GEM sends a ground signal to the instrument cluster.
SECTION 413-01: Instrument Cluster
1999 Mustang Workshop Manual
DIAGNOSIS AND TESTING
Procedure revision date: 08/19/2002
Special Tool(s)
New Generation STAR (NGS) Tester
418-F048 (007-00500) or equivalent
Instrument Gauge System Tester
014-R1063 or equivalent
73 Digital Multimeter
105-R0051 or equivalent
Page 1 of 32
1999 Mustang Workshop Manual
1/18/2013
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