Electrical 389 Family
Peterbilt Motors Company 6-11
If part of the panel has gauges backlit and some of the gauges are not backlit, the jumper harness wire between
the gauges is probably not connected properly.
If a 2-inch electronic gauge has power (yellow wire) and ground (green wire) but is not receiving data (blue wire),
then the red indicator lamp at the 6 o’clock position of the gauge blinks after 30 seconds of waiting for data. This
indicates there is an open or short in the blue wire between the gauge and the ICU/CECU.
If the red indicator lamp is on but the gauge is operational, it indicates the value is out of normal range.
If a 2-inch electronic gauge has a short or open in the sensor wiring, the gauge needle moves 5° below the first
tick mark (approximately one needle thickness).
Optional mechanical gauge (such as air suspension) needles are driven mechanically with air pressure. There is
no red warning lamp and the backlighting is through the brown wire from the ICU/CECU (a PWM input). The 4-
way jumper harness is still used to pass all 4 circuits through the gauge to the next gauge in the chain.
Specialty CVSG gauges (such as the clock, PTO hour meter, and transmission display) are stand-alone gauges
and are independent of the ICU/CECU.
Instruments and Controls Operation
Before attempting to repair any instrumentation problems, the technician should have a complete understanding of how
the instruments and controls operate.
Speedometer The Speedometer indicates the vehicle speed in miles per hour (mph) and in kilometers per hour (km/h).
Tachometer The Tachometer measures the engine speed in revolutions per minute (rpm).
Air Filter Restriction Pressure The Air Filter Restriction Pressure gauge indicates the condition of the engine air cleaner
and is measured by inches of water (H
2
O). A clean filter should register 7 in. H
2
O (may vary with system design) and a
filter whose life is over registers approximately 25 in. H
2
O.
Air Starter Pressure The Air Starter Pressure Gauge indicates the amount of air pressure in the air start reservoir.
Ammeter The Ammeter monitors the vehicle’s electrical system and makes sure the system is in balance and operating
normally. If not, it may be drawing power from the alternator (positive reading) or from the batteries (negative reading).
Under normal conditions the ammeter will read nearly “zero.”
Axle, Drive Oil Temperature The Drive Axle Oil Temperature gauges (front, rear, and center) indicate the temperature of
the lubricant in the vehicle’s axles.
Axle, Pusher Air Pressure, #1, #2, #3 The Pusher Axle Air Pressure gauges indicate the air pressure in each of the
pusher axles suspension air bags.
Axle, Tag Air Pressure The Tag Axle Air Pressure gauge indicates the amount of air pressure in the tag axle suspension
air bags.
Brake, Application Air Pressure The Brake Application Air Pressure gauge indicates how much air pressure is being
applied from the foot brake valve or trailer brake hand valve to the air brakes.
BrakeSaver Application Air Pressure (Export vehicles only) The BrakeSaver Application Air Pressure gauge indicates
the amount of air pressure applied to the BrakeSaver hand control valve.
BrakeSaver Oil Temperature (Export vehicles only) The BrakeSaver Oil Temperature gauge indicates the temperature
in the BrakeSaver. If the oil temperature exceeds the maximum limits, a red warning lamp in the gauge turns on.
