Check Engine Lamp

171

TM 9-2320-312-24-2

Troubleshooting Section

The flash codes are two-digit representations of

Use the following information in order to determine

diagnostic codes. The PID-FMI diagnostic code

if the check engine lamp is operating incorrectly:

should be used for troubleshooting. The PID is the

Parameter Identifier. The FMI is the Failure Mode

The check engine lamp is the only standard lamp

Identifier. A 110-03 is an example of a PID-FMI

that is used.

Diagnostic Code. Flash codes provide an indication

of a failure. Flash codes are not as specific as

The following background information is related

diagnostic codes. Flash codes only indicate that a

to the following procedure:

failure has occurred. Flash codes do not indicate

the specific type of failure. For example, the flash

Check Engine Lamp

code (27) is used for a 110-03 fault code and a

110-04 fault code. Flash codes should not be used

The check engine lamp is used to provide the

for troubleshooting.

following functions:

Indicate the existence of an active diagnostic

Diagnostic flash codes that are active can be

viewed at any time. Turn the Cruise Control On/Off

code.

switch to the OFF position. Hold the Set/Resume

Indicate driver alert status of the Idle Shutdown

switch in either the SET position or the RESUME

position until the lamp begins to flash. Then release

Timer.

the Set/Resume switch.

Read diagnostic flash codes.

The flash code is determined by the blinking of the

check engine lamp. The lamp will blink for the first

Power Up Lamp Check

digit of the flash code, and the lamp will pause

for five seconds. Then, the lamp will blink for the

At powerup, the lamp will turn ON for five seconds.

second digit.

The lamp will continue to flash if there is an active

diagnostic code.

Some vehicles are equipped with a diagnostic

enable switch. The diagnostic enable switch is used

Operation with an Active Diagnostic Code

to flash the diagnostic codes by grounding the

input of the diagnostic enable switch from terminal

While the engine is operating, the lamp will turn ON

46 (Input 7) to terminal 5 (sensor common).

for a minimum of five seconds when certain fault

conditions exist. If certain fault conditions exist, the

Note: The check engine lamp should not

lamp will operate in the following manner:

continuously flash the diagnostic flash codes. If the

The check engine lamp will turn ON for five

set switch, the resume switch, or the diagnostic

enable switch has not been used, then the circuit is

seconds.

probably shorted to ground.

The check engine lamp will turn OFF for a short

Electrical Connection of the Check Engine Lamp

time.

The check engine lamp will turn ON for another

One terminal of the check engine lamp must be

connected to battery voltage through the vehicle

five seconds.

wiring. The other terminal is connected to the ECM

at the vehicle harness connector J1/P1 terminal 28

The check engine lamp will continue to operate in

(check engine lamp).

this manner while the fault condition exists.

The ECM provides a path to ground in order to turn

Indication of the Driver Alert Status of the Idle

the lamp ON.

Shutdown Timer

During the final 90 seconds of the operation of the

Idle Shutdown Timer, the check engine lamp will

begin to flash. The flashing of the check engine

lamp indicates that an engine shutdown is near.

Flashing Out Diagnostic Flash Codes