Table 1. 637 Backup Alarm Diagnostic Codes.
CID FMI CODE
TEST OR INSPECTION
637-3 Backup Alarm Circuit
Voltage Is Above Normal
· Always inspect wiring harness connectors that are involved in the circuit.
Poor connections can often be the cause of a problem in an electrical
circuit. Verify that all connections in the circuit are clean and secure and
that all connections are in good condition. If a problem with the
connection is found, correct the problem and verify that this malfunction
or diagnostic code is active before performing this procedure.
· Perform open or short-circuit test at each wiring harness connection to
identify the correct wiring harness to replace.
· Tag all wiring harnesses to aid in installation.
· Perform this test only if condition is active.
DIAGNOSTIC CODE SET CONDITION
Transmission ECM detects voltage of the backup alarm circuit is above normal.
· Lower cab wiring harness is shorted to another power source.
· Rear frame wiring harness is shorted to another power source.
· Transmission ECM.
Test Step 1. Check for Active
1. Connect MSD. Select
2. Turn military light switch to
SER. DRIVE position (TM 5-3805-
3. Place transmission control switch
Diagnostic Code 637-3 Active -
Proceed to Test Step 2.
in R position (TM 5-3805-298-10)
and check for active diagnostic
Diagnostic Code 637-3 Not Active -
Troubleshooting is complete.
Test Step 2. Test for Shorted Rear
Frame Wiring Harness.
1. Turn ignition switch and battery
disconnect switch to OFF position