Car Maintenance Guide
Warning Lights

The best warning lights are those that can have only one interpretation.

Unfortunately, manufacturing costs sometimes force auto designers to combine several warning signals in a single dashboard indicator. That makes it harder for drivers to understand the message provided by a warning light and react to unexpected warnings without panic.

The two most common warning signals, for water temperature and oil pressure, are frequently combined in a single "engine" light to report a problem of either kind. When the engine light comes on, drivers must expect the worst: oil pressure loss and turn the engine off immediately. With separate warning lights or auxiliary gauges, a driver can distinguish a minor overheating situation from a much more expensive to repair oil pressure loss. All cars built since 1981 have a built-in self diagnostic system with a "check engine" or "power loss" warning light. That light provides a significantly different warning than the "engine" light. "Check engine" identifies a malfunction in the computerized engine controls under the hood.

Usually this warning light does not call for emergency attention. Still, prompt attention can keep the situation from worsening.

The "brake" warning light can be confusing, too. It usually indicates that the parking brake is engaged. Yet it also can indicates one or more of the following conditions on various cars: brake fluid is low in the reservoir, power assist for the brake system has failed, one of the dual braking systems has failed.

Beware of the alternator or charging system warning light! Your battery may become run down and this warning indicator may never light up. The warning light checks only the presence of electrical "pressure", commonly known as voltage, coming from the alternator. A loose drive belt can allow electricity to be present, but not in sufficient amounts to keep the battery charged. Also, a malfunctioning trunk light can cause a constant load on the battery, even when the car is parked.

To prepare for warning light conditions during driving:

• Clarify the exact interpretation of your car's warning lights by reading or re-reading the owners manual.
• Plan a mental course of action in advance for what to do should a given warning light come on while driving.
• Compare the owner's manual of each car you own to understand the similarities and differences in warning lights that appear to be identical.
• When shopping for a new car, consider optional gauge packages that make it easier to interpret warning light messages.

When a warning light comes on while driving, do not reach for the operating manual and fumble through it for emergency answers. Read and understand it in advance, and then you can be calm and cool when the unexpected happens.