Engine Controls - Basic Testing: Introduction
NOTE:
The CHECK ENGINE light is now referred to as Malfunction Indicator Light (MIL). The MIL is displayed in instrument cluster as CHECK ENGINE. Electronic Control Module (ECM) may also be referred to as Powertrain Control Module (PCM).
The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for no-start condition.
The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under the conditions the problem reportedly occurred.
Before entering self-diagnostics (if equipped), perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.
NOTE:
Preform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm impedance. Unless stated otherwise in test procedure.