TM-9-2320-272-23-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5
SEPTEMBER 2012
TM-9-2320-272-23-1 - Page 1266 of 1313
FIELD MAINTENANCE
LOSS OF AMBER WARNING LIGHT AND/OR OVERSPEED LIGHT
INITIAL SETUP:
Tools and Special Tools
Tool Kit, General Mechanic's: Automotive
(Volume 5, WP
0826, Table 1, Item 56)
Multimeter
(Volume 5, WP
0826, Table 1, Item 34)
Test Set, Electronic Systems
(Volume 5, WP
0826, Table 1, Item 51)
Personnel Required
(2)
References
Point to Point Schematics
References (cont.)
Volume 2, WP
0321
Volume 2, WP
0322
Volume 2, WP
0323
Volume 5, WP
0813
Equipment Condition
Vehicle parked and engine shut down.
(TM
9-2320-272-10)
TROUBLESHOOTING PROCEDURE
LOSS OF AMBER WARNING LIGHT AND/OR OVERSPEED LIGHT
NOTE
•
Conduct these malfunction tests if there is a loss of amber warning light or overspeed
light. This procedure will check for a faulty light bulb, Electronic Control Unit (ECU), CTIS
wiring harness, vehicle wiring harness connections, and speed signal generator.
•
The CTIS incorporates an over speed warning and an automatic pressure increase to
prevent operation of the vehicle with insufficient tire pressure. This system incorporates
a sensor to measure vehicle speed, a panel mounted flashing light, and a connection to
the vehicle blackout lights to prevent flashing of the amber warning light when the vehicle
is operating under blackout conditions. The ECU periodically measures the speed of the
vehicle and compares the speed to programmed limits. If these limits are exceeded, the
warning light and automatic pressure increase functions are actuated.
STEP
1.
IS THE AMBER WARNING LIGHT OUT WHEN THERE IS AN OVERSPEED PRESSURE CHANGE?
Verify there was an overspeed pressure change.
CONDITION/INDICATION
IS THE AMBER WARNING LIGHT OUT WHEN THERE IS AN OVERSPEED PRESSURE CHANGE?
DECISION
YES - Amber light problem. Go to Step (2).
NO - Overspeed light problem. Go to Step (5).
TM 9-2320-272-23-1
0150
0150-1
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