Check Engine Lamp or Warning Lamp Is Malfunctioning

TM 9-2320-312-24-2

Troubleshooting Section

Recommended Actions

b. Check the fuel quality. Refer to Testing and

Adjusting, "Fuel Quality - Test". Also refer

to the Truck Performance and Driveability

Note: GM vehicles refer to the Check Engine

Diagnostic Guide, LEBT3477.

Lamp as the Service Engine Soon Lamp.

c. Check the fuel pressure. Refer to Testing and

Perform the following diagnostic procedures in

Adjusting, "Fuel System Pressure - Test".

order:

d. Ensure that the fuel system has been primed.

Intermittent Diagnostic Codes

Refer to Testing and Adjusting, "Fuel System

- Prime".

Check for logged diagnostic codes and active

diagnostic codes with Caterpillar Electronic

e. Check for fuel supply lines that are restricted.

Technician (ET). Check for any intermittent

diagnostic codes.

f. Check the fuel filters.

Check Engine Lamp

g. If the temperature is below 0 C (32 F), check

for solidified fuel (wax).

1. In order to check the check engine lamp, turn

the ignition key to the ON position while the

h. Check for air in the fuel system. Refer to

engine is OFF.

Testing and Adjusting, "Air in Fuel - Test".

The check engine lamp should turn on. Then,

8. Check the Air Inlet System for restrictions

the check engine lamp should turn off. The

or leakage. Check the Exhaust System for

check engine lamp will flash if there is an active

restrictions or leakage. Refer to Testing and

diagnostic code.

Adjusting, "Air Inlet and Exhaust System -

Inspect".

a. If the check engine lamp does not operate

correctly remove the check engine lamp

9. Check for leakage in the Air-to-Air Aftercooler

(terminal 28) from the ECM connector (seventy

Core . Refer to Testing and Adjusting, "Aftercooler

terminal).

- Test".

b. Connect the check engine lamp (terminal

i01641503

28) to the ground stud. Turn the ignition key

switch to the ON position.

Check Engine Lamp

or Warning Lamp Is

c. Observe the check engine lamp.

Malfunctioning

If the check engine lamp comes on, check the

power connection and the ground connection

SMCS Code: 7400; 7569

of the ECM. Refer to Troubleshooting, "Check

Engine Lamp Circuit - Test" for additional

Probable Causes

information.

If the lamp does not come on, check the lamp

The probable root causes are listed in order below:

in order to ensure that the lamp is not burned

Intermittent diagnostic codes

out. Also, check the wiring in order to ensure

that there is not an open circuit.

Check engine lamp

Warning Lamp

Warning lamp

1. In order to check the warning lamp, start the

Cruise control set/resume switch

engine.

Short in vehicle harness

The warning lamp should come on for at least 2

seconds. Then, the warning lamp should turn off.

Service engine soon lamp (GM)

The warning lamp will remain on or flash if there

is a problem with the engine.