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HOMESERVICE MANUALSCHEVROLET1994SUBURBAN C2500, 7.4 NREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SYSTEM/COMPONENT TESTS - 6.5L DIESELINTRODUCTION
1994 Chevrolet Suburban C2500, 7.4 N

Engine Controls - System/Component Tests - 6.5L Diesel: Introduction

1994 Chevrolet Suburban C2500, 7.4 NSECTION Introduction

Before testing separate components or systems, perform procedures in BASIC TESTING - 6.5L DIESEL article in this section. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in appropriate TESTS W/CODES article in this section below.

  • G - TESTS W/CODES - 6.5L DIESEL (for "C" & "K" Series)
  • G - TESTS W/CODES - 6.5L DIESEL (for "G" & "P" Series)
NOTE: Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter and refer to WIRING DIAGRAMS  to isolate wiring harness shorts or opens.

The following table provides the location of commonly used diagnostic information. These former "A" and "C" charts are now written in text and inserted into the new Engine Performance workflow. To familiarize yourself with the Engine Performance workflow, see the AA - USING THIS SECTION (GENERAL HELP INFORMATION) article in this section.

GENERAL MOTORS "A" & "C" CHART REFERENCE

System or Component Diagnostic Information Location
DIAGNOSTIC CIRCUIT CHECK (1) See DIAGNOSTIC CIRCUIT CHECK
A-1 & A-2, Malfunction Indicator Light (MIL) (1) See DIAGNOSTIC CIRCUIT CHECK
A-3, No-Start (1) See NO-START DIAGNOSIS
A-5, Fuel Pump Relay See RELAYS, SOLENOIDS, MOTORS & MODULES 
A-6 & A-7, Fuel System Diagnosis (1) See BASIC FUEL SYSTEM CHECKS
C-1, MAP Sensor See ENGINE SENSORS & SWITCHES 
C-1, Power Steering Pressure Switch See ENGINE SENSORS & SWITCHES 
C-1, Park/Neutral Switch See ENGINE SENSORS & SWITCHES 
C-3, Canister Purge System See EMISSION SYSTEMS & SUB-SYSTEMS 
C-6, Air Injection System See EMISSION SYSTEMS & SUB-SYSTEMS 
C-8, Torque Converter Clutch See MISCELLANEOUS ECM CONTROLS 
C-8, Manual Trans. Shift Lights See MISCELLANEOUS ECM CONTROLS 
C-10, A/C Clutch Control See MISCELLANEOUS ECM CONTROLS 
C-12, Electric Cooling Fan Control (2) See MISCELLANEOUS ECM CONTROLS 
(1) See BASIC TESTING - 6.5L DIESEL article in this section.
(2) Covered in entirety in appropriate ENGINE COOLING article.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.