Engine Controls - Basic Diagnostic Procedures: Introduction

Most driveability or no-start problems are not related to computerized engine control systems, but result from simple mechanical breakdowns, poor electrical connections, or fuel or vacuum related faults.

Before condemning the computer system, perform a careful and complete inspection of ignition high tension wires, fuel supply, electrical connections and vacuum hoses. Failure to do so may result in improper diagnosis or lost diagnostic time.

The first step in diagnosing a driveability problem is to verify the problem actually exists by test driving the vehicle under conditions the problem reportedly occurred.

If a no-start or driveability condition is being caused by a non-computer related problem, the following diagnostic steps can help you discover the problem.

NOTE: All voltage tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in testing procedures.