Test Notes

Enter this pinpoint test only when directed here from symptom flowcharts.

To prevent the replacement of good components, be aware that the following non-EEC areas may be at fault:
- fuse, bulb or socket

This pinpoint test is intended to diagnose only the following:
- STO/MIL circuit
- Powertrain Control Module (PCM)

Description
The CHECK ENGINE light is intended to alert the driver of certain concerns in the closed loop system. The CHECK ENGINE light output is turned on when the strategy detects a concern in certain input/output circuits. The light will remain on as long as the concern is present. Regulations governing this light also require that the Diagnostic Trouble Codes (DTCs) be displayed by the flashing of this light.

CHECK ENGINE Light Functionality
The CHECK ENGINE light is located in the instrument cluster and is amber colored. The CHECK ENGINE light functions in one of three modes.
1. Bulb check - At key-ON the light is turned on for a short duration as a bulb check. If this does not occur, check the wiring, the bulb, and the associated fuse.
2. Detection of certain concerns - The CHECK ENGINE light is used to indicate that one of certain concerns has been detected by the PCM or IDM. Only those concerns which result in a change in power output available from the engine will cause the light to be turned on. Examples of such concerns are:
a. Injector low side short to ground - The PCM will turn off four cylinders to prevent engine damage.
b. Accelerator pedal sensor out of range - The PCM will allow the engine to idle only.