Engine Controls - Basic Testing: Introduction

The following diagnostic steps can help prevent overlooking simple problems. This is also the place to start diagnosing a no-start condition.

The first step in diagnosing any driveability problem is to verify the problem exists. This may be accomplished by test driving the vehicle under the conditions during which the problem reportedly occurs.

Before entering self-diagnostics, perform a careful and complete inspection of several systems. Most driveability or no-start problems are not related to computerized engine control systems, but are usually simple mechanical, electrical, fuel or vacuum problems. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged or misrouted vacuum hoses.

Before considering the computer system as a possible cause of problems, check ignition high tension wires, fuel supply, electrical connections and vacuum hoses. Failure to check these items can result in improper diagnosis or lost diagnostic time.