Auto Repair Help
JIM’S CORNER – AUTO REPAIR HELP

DIAGNOSE – The “CHECK ENGINE” LIGHT CAME ON
by Jim Miller

SYMPTOM SUMMARY
The “Service Engine Soon” or “Check Engine” light comes on while the engine is running.

USUAL CAUSE
The vehicles electronic control unit constantly monitors and adjusts various engine parameters. If the control unit detects a failure in one of the connected circuits, it will illuminate the malfunction indicator lamp and wll store a diagnostic trouble code in its memory that corresponds to the failed circuit. If the malfunction indicator light is on, the computer has detected a malfunction in the engine management system.

DIAGNOSIScheckengine
The diagnosis of the symptom requires interfacing with the on-board computer and retrieving the stored diagnostic trouble code. Manufacturers troubleshooting procedures are then used for the specific trouble code that was retrieved. A special hand held computer, usually referred to as a scan tool, is required to interface with the computer. However, some manufacturers use the malfunction indicator lamp to flash a series of blinks to indicate the specific code. On these vehicles, diagnostics are usually entered by grounding or connecting a pair of diagnostic connectors. Once connected, the computer transmits the stored code(s) to the lamp. The lamp flashes are counted to determine the corresponding code. You will need to refer to the manufacturer specific repair manual to determine the type of system utilized on your vehicle.

PRECAUTIONS, TIPS, and NOTES
Working on the computer system requires a good working knowledge of electrical system theory and the proper testing equipment. The computer system can be damaged by using the incorrect test procedures. There are relatively inexpensive test equipment available to retrieve the diagnostic codes from the most common vehicles. Consult your auto parts store for availability.

(Jim is a lifelong fan of Dodger Baseball and used to race sprint cars in the 1980s.)

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2 Comments on "Check Engine Light Came On"

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Gowrishankar
3 years 8 months ago

My Nissan Altima 2004 is showing service engine soon light and is not starting.Give me a solution for this

2 years 9 months ago

si mi atos 2006 prende check y como k testerea cuando va avansando cual sera la falla, es grave seguir usandolo.

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