MARINE ELECTRONIC FUEL INJECTION (MEFI) - DIAGNOSTIC MANUAL - Safety and Service Instructions

Oct 24, 2026

Service and diagnostic manual for GM Marine Electronic Fuel Injection (MEFI) engines, providing safety-focused service precautions and procedures for fuel control and ignition systems. Covers general descriptions and effective diagnostic methods, including how cautions and notices reduce risks during service or repair. Includes guidance on replacement parts and fastener handling, references to onboard diagnostics, reading and clearing diagnostic trouble codes (DTCs), and the use of scan tools and testing workflows. Intended for qualified technicians and boat owners with proper training.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages286

Reading Time12 h 1 min

AccessFree to download

General Information

General Description

Visual/Physical Inspection

Basic Knowledge and Tools Required

Electrostatic Discharge Damage

Engine Wiring

Engine Control Module (ECM) Self-Diagnostics

Malfunction Indicator Lamp (MIL)

Reading Diagnostic Trouble Codes (DTCs)

On-Board Diagnostic (OBD) System Check

DLC Scan Tools

Scan Tool Use With Intermittents

How Diagnostic Trouble Codes Are Set

Clearing Diagnostic Trouble Codes

Service Precautions

Special Tools (1 of 2)

Special Tools (2 of 2)

Abbreviations

Diagnosis

On-Board Service

Wiring Harness Service

CAUTION To reduce the chance of personal injury and/or property damage, the following instructions must be carefully observed. Proper service and repair are important to the safety of the service technician and the safe, reliable operation of all System4 Electronic Fuel Injection equipped engines. If part replacement is necessary, the part must be replaced with one of the same part number or with an equivalent part. Do not use a replacement part of lesser quality. The service procedures recommended and described in this service manual are effective methods of performing service and repair. Some of these procedures require the use of tools speciﬁcally designed for the purpose. Accordingly, anyone who intends to use a replacement part, service procedure, or tool which is not recommended by the manufacturer, must ﬁrst determine that neither his safety nor the safe operation of the vehicle will be jeopardized by the replacement part, service procedure or tool selected. It is important to note that this manual contains various Cautions and Notices that must be carefully observed in order to reduce the risk of personal injury during service or repair, or the possibility that improper service or repair may damage the vehicle or render it unsafe. It is also important to understand that these ‘Cautions’ and ‘Notices’ are not exhaustive, because it is impossible to warn of all the possible hazardous consequences that might result from failure to follow these instructions. MARINE ELECTRONIC FUEL INJECTION (MEFI) DIAGNOSTIC MANUAL At the beginning of each individual section is a Table of Contents which gives the page number on which each subject begins. When reference is made in this manual to a brand name, number or specific tool, an equivalent product may be used in place of the recommended item. All information, illustrations and specifications contained in this manual are based on the latest product information available at the time of publication approval. The right is reserved to make changes at anytime without notice. NOTICE: When fasteners are removed, always reinstall them at the same location from which they were removed. If a fastener needs to be replaced, use the correct part number fastener for that application. If the correct part number fastener is not available, a fastener of equal size and strength (or stronger) may be used. Fasteners that are not reused, and those requiring thread locking compound will be called out. The correct torque value must be used when installing fasteners that require it. If the above conditions are not followed, parts or system damage could result. GM POWERTRAIN DIVISION SERVICE OPERATIONS General Motors Corporation Ypsilanti, Michigan General Motors Corporation/ Technical Services, Inc. All rights reserved September 2005 Printed in Syracuse, IN USA No part of this publication may be reproduced, stored in any retrieval system, or transmitted, in any form or by any means, including but not limited to electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the GM Powertrain Division of General Motors Corp. This includes all text, illustrations, tables and charts. FOREWORD This service manual includes general description, diagnosis, symptoms and on-board service procedures for the fuel control and ignition systems used on GM equipped Marine Electronic Fuel Injection (MEFI) engines. INTRODUCTION The following manual has been prepared for effective diagnosis of the Marine Electronic Fuel Injection (MEFI) system. All information, illustrations and specifications contained in this manual are based on the latest product information available at the time of publication approval. The right is reserved to make changes at anytime without notice. This manual should be kept in a handy place for ready reference. If properly used, it will meet the needs of technicians and boat owners. GM Powertrain Division servi

FAQs

What safety precautions does the manual emphasize before servicing MEFI engines?

It stresses carefully observing cautions to reduce personal injury and property damage. It also warns that improper service or repair can damage the vehicle or render it unsafe.

How should replacement parts and fasteners be handled during service?

Replacement parts must match the same part number or an equivalent of equal or better quality. Fasteners should be reinstalled in the original location and use the correct torque and part number when replacement is required.

What core diagnostic topics does this manual cover for MEFI systems?

It includes general diagnostic preparation, onboard service, engine wiring topics, ECM self-diagnostics, MIL behavior, reading and clearing DTCs, and OBD system checks using scan tools.

Oct 24, 2026

Upload by AditGamingID