TM 9-2320-363-20-1
Section 2
BASIC KNOWLEDGE REQUIRED (Cont'd.)
E. GENERAL DIAGNOSTIC INFORMATION
As a bulb and system check, the "Check Engine", and "Stop Engine" lights will come on for 5 seconds when the ignition
switch is first turned on. If the unit is programmed for the cruise control feature, the "Cruise Active" light (if equipped) will
also turn on for 5 seconds.
If the "Check Engine" light comes on during vehicle operation, this indicates the self diagnostic system has detected a
fault.
When the diagnostic request switch is held, the diagnostic system will flash the yellow or red light located on the vehicle's
dash. The light will be flashing the code(s) indicating the problem area(s). If the "Stop engine" light comes on during
vehicle operation, this indicates the DDEC System has detected a potential engine damaging condition. The engine
should be shutdown immediately and have the engine checked for the problem.
*Active codes will be flashed on the stop engine light in order from most recent to least recent occurrence based on
engine hours. If there are no active codes, a code 25 will be flashed.
*Inactive codes will be flashed on the check engine light in order from most recent to least recent occurrence based on
engine
hours. If there are no inactive codes, a code 25 will be flashed.
*FLASHING CODES SHOULD BE DONE WITH THE ENGINE NOT RUNNING AND IGNITION ON. *
A diagnostic code indicates a problem in a given circuit (i.e., diagnostic Code 14 indicates a problem in the oil or coolant
temperature sensor circuit. This includes the oil or coolant temperature sensor, connector, harness, and Electronic
Control Module (ECM). The procedure for finding the problem can be found in Diagnosis Chart Code 14. Similar charts
are provided for each code. Remember, diagnosis should always begin at the starting chart (START). For an oil or
coolant temperature sensor problem, it will quickly lead you to Chart 14 - but first it gets you to verify the code/symptom.
Since the self-diagnostics do not detect all possible faults, the absence of a code does not mean there are not problems in
the system. If a DDEC III problem is suspected, even in the absence of a code, go to START anyway. This chart can
lead you to other charts which can aid in the troubleshooting process - where DDEC III problems may occur but do not
generate a code. Basic mechanical checks, however, are not covered in this guide.
Change 3 3-345.13
