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Checking the Check Engine Lamp


CHECKING THE CHECK ENGINE LAMP FOR FUEL-INJECTED ENGINES

Fuel-injected vehicles have a system indicator lamp on the instrument panel that may be labeled CHECK ENGINE. It not only signals problems with sensors and actuators, it also is an important device for checking the computer's ability to communicate with the scanner. If the scanner cannot communicate with the vehicle or perform some tests, disconnect the scanner and see if the computer will flash fault codes on the lamp.

Bulb Check

Turn the ignition on and verify that the CHECK ENGINE lamp lights with the ignition on and the engine off. If It does not, troubleshoot and repair the problem before going farther. It could be as simple as a burned out bulb or a blown fuse. It also could indicate a system computer problem. Refer to Diagnostic Charts.

Extracting Codes

If the CHECK ENGINE lamp passes the bulb check, cycle the ignition key ON - OFF - ON - OFF - ON, leaving it on the third time.


The CHECK ENGINE lamp should flash on and off in even pulses to indicate any codes present in the computer. The lamp should flash in this sequence:

1. The lamp should light for about 2 seconds after the ignition is cycled to ON the third time. Then It should go out for about 2 to 4 seconds.

2. The lamp should flash any fault codes present in the computer. The lamp will flash each code one time.

3. The lamp should flash code 55 as a series of: 5 flashes - pause - 5 flashes.

The last series of flashes, code 55, means "end of fault code transmission." If the lamp flashes only code 55, no other codes are present in the computer.

NOTES:

If the lamp stays lit continuously, if it flickers unevenly, or if it does not flash at least a code 55, the computer is not entering the diagnostic mode. Refer to Diagnostic Charts.

Remember, the scanner must be disconnected from the vehicle diagnostic connector to flash codes on the CHECK ENGINE lamp.

Vehicles with carbureted engines do not have an instrument panel POWER LOSS, POWER LIMITED, or CHECK ENGINE lamp.
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