What Are the Causes a Check Engine Light Being On?

The first generation of On-Board Diagnostic [OBD-1] systems of the early 1980s used a red or amber Check Engine dashboard light to alert the driver of an abnormal operation in one or more of the vehicle emission systems. However, the OBD-1 program was a broad, self-diagnostic system and was used as a general guide by auto technicians to locate engine trouble areas.

Causes

A check engine light could indicate an inoperative engine coolant sensor, oxygen sensor, throttle position sensor, crankshaft position sensor, speed sensor; or a problem with the engine thermostat, exhaust gas recirculation system, distributor signal, idle air control motor, charging system and several other components or circuits.

Function

Once your vehicle computer detects a malfunction in one or more of these systems, it will store a trouble code in its memory and turn on the check engine dashboard light to alert you about the problem.

Types

Early On-Board Diagnostic systems used variations of the check engine dashboard light like the "Service Engine Soon" and similar messages. Even alphanumeric trouble codes and computer harness connectors to retrieve these codes varied form one manufacturer to another.

Benefits

It is a useful system that drivers and auto technicians can use to locate a possible malfunction.

Retrieval

Drivers or auto technicians can retrieve this trouble codes with the use of a scan tool or some other system determined by the car manufacturer, states Mike Stubblefield in The Haynes Emissions Control Manual.

References

• The Haynes Emissions Control Manual; Mike Stubblefield and John H. Haynes; 2001
• Modern Automotive Technology; James E. Duffy; 2003