DDEC II Operation.

TM 9-2320-364-20-1

(c)

Ten NUMERIC KEYS arranged calculator-style for quick operation. Each key is imprinted with a

single digit.

To the right side of the keypad, there are four arrow keys, each imprinted with a direction

arrow. The UP and DOWN arrow keys are used to scroll through the lines of the display.

Each touch of a key causes the display to move one line, up or down. The LEFT and RIGHT

arrow keys are used to toggle back and forth between choices given by the display; they may

have other purposes, depending on which cartridge is used.

The FUNC key, below the arrow keys, lets you choose various DDR modes, or functions,

depending on the cartridge in use. These include several operating modes and a printing mode.

The ENTER key lets you tell the DDR when to do something. Depending on what's showing

in the readout window display, the ENTER key can make a selection, confirm an answer, or

instruct the DDR to continue to the next step.

(6)

RS232 port. On the right side of the DDR case is an RS232 port. Using the proper cables, you can

connect to a printer or terminal.

(7)

DDL connector. The DDR receives information from the truck's on-board computer, the DDEC

electronic control module (ECM) ATEC electronic control unit (ECU), through a connector called the

Display Data Line (DDL). The DDL has 12 terminal cavities. The DDL adapter plug is located on the

left side of the cab at left door hinge area under the edge of the instrument panel.

DDEC II Operation.

(1)

General instructions.

(a)

The Check Engine Light (CEL) and Check Gages Light (CGL) will light for five seconds when the

ENGINE switch is first turned ON as a bulb and system check. If the Check Engine Light remains

on, the self-diagnostic system has detected a fault.

(b)

The first step in diagnosis is identifying the symptom or problem condition. Always refer to DDEC

II Troubleshooting (All Conditions) to begin troubleshooting.

Symptom A

CEL comes on and stays on

Symptom B

CEL is always off

Symptom C

CEL operates normally (comes on for up to 5 seconds, then goes off) and a

fault is present

Symptom D

CEL and fault are intermittent

Symptom E

Engine cranks but will not start

Symptom F

CGL is always on or always off

(c)

Once the key symptom is identified, refer to the fault index to find the page number of the flowchart

for that symptom. Symptoms A, C, D and F's starting flowcharts will list secondary symptoms

(Symptoms B and E have no secondary symptoms). Look to the right of the secondary symptom to

find the page on which to begin troubleshooting. Go to that page.

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