CHART - 9 - DIAGNOSTIC REQUEST SWITCH INOPERATIVE

TM 9-2320-364-20-1

2-14. DDEC III/IV TROUBLESHOOTING (CONT).

Section IV. TROUBLESHOOTING CHARTS (Cont.)

D. CHART - 9 - DIAGNOSTIC REQUEST SWITCH INOPERATIVE

NOTE - This chart is only to be used if:

1) All basic mechanical checks and physical inspections have been performed with no problem found; and,

2) Diagnosis of DDEC III/IV was started at step START-1, pg 2-539, and you have now been referred here.

STEP/SEQUENCE

RESULT

WHAT TO DO NEXT

C 9-1

Check Diagnostic

Request Circuit

Turn ignition on/engine

Display reads "ON".

Go to C 9-2.

not running.

Plug in DDR.

Select SWITCH/LIGHT STATS

Depress and hold diagnostic

Display reads "OFF".

Diagnostic request line (#528)

request switch.

is open, or is not being grounded

Observe "Diagnostic Request"

when switch is depressed. Check

status on DDR.

#528 wire and ground for

diagnostic request switch. Repair

problem then go to C 9-30.

Display reads "N/A".

Replace ECM (para 7-57).

C 9-2

Check CGL/CEL Bulb

Turn ignition off.

Bulb is okay.

Go to C 9-3.

Remove CEL and CGL Bulb,

check to see if it is burned out

Bulb is not okay.

Replace bulb(s) (para 7-24).

or damaged.

Then go to C 9-30.

C 9-3

Check Ignition Line

Turn ignition off.

Disconnect vehicle harness

Less than

DDEC ignition circuit breaker

connector at ECM.

11.5V.

(CB13) is blown and/or ignition

Read voltage at cavity B3 (#439).

line is open or shorted to

ground.

Greater than 11.5V.

Ckt #419 or #509 is open.

Repair open and go to C 9-30.

2-605