CHART - 4 - NO "CHECK ENGINE" LIGHT DURING BULB CHECK OR CANNOT CLEAR CODES

TM 9-2320-364-20-1

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

Section IV. TROUBLESHOOTING CHARTS (Cont.)

D. CHART - 4 - NO "CHECK ENGINE" LIGHT DURING BULB CHECK OR CANNOT CLEAR CODES

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 4- 1

Try to Force CEL On

Plug in DDR.

DDR display is

Go to C 4--2.

Turn ignition on.

blank or random.

Select ACTIVATE OUTPUTS.

Activate "Check Engine" light.

"Check Engine"

Go to C 4--2.

light is still off.

"Check Engine"

Go to C 4--4.

light is still on.

C 4- 2

Check for Ignition

Read voltage on vehicle harness

Less than 10.0 volts.

The DDEC ignition circuit breaker

connector, socket B3 (red lead)

(CB13) is blown and/or

to a good ground (black lead)

ignition wires are open or

with the ignition on and engine

shorted to ground, and/or the

off.

ignition line (ckt #439) is shorted

to ground or is not wired to

switch ignition source (See note

below). Repair problem. Then

go to C 4-30.

Greater than

Go to C 4--3.

or equal to 10.0 volts.

C 4- 3

CEL Drive Line and Bulb

Check

Turn ignition off.

Bulb is

CEL driver line (ckt #419) or

Remove CEL bulb and check

okay.

ground line (ckt #150) is open.

whether it's burned out or

Repair open. Then go to C 4-30.

otherwise damaged.

Bulb is

Replace bulb (para 7-24). Then

not okay.

go to C 4-30.

*NOTE: Inactive codes will not clear and engine hours/fuel consumption values will not update if main ECM

power (ckt #240 and #241) is switched off with or before ignition.

2-579