Engine Controls - Basic Diagnostic Procedures: Introduction

NOTE: Dakota and Durango equipped with the Jeep/Truck Engine Controller (JTEC) Powertrain Control Module (PCM) are equipped with a separate Transmission Control Module (TCM). Durango equipped with the Next Generation Controller (NGC), has a PCM and TCM combined into a single controller. The JTEC PCM has 3 harness connectors (Black C1, White C2 and Gray C3). The NGC PCM has 4 harness connectors (Black C1, Gray C2, White C3 and Green C4).

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a 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, 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: Unless stated otherwise in test procedure, perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) having a minimum 10-megohm input impedance.