Engine Controls - Basic Testing: Introduction
The following diagnostic steps help prevent overlooking simple problems and begin diagnosis for no-start conditions.
The first step in diagnosing any driveability problem is verifying the customer's complaint by test driving vehicle under the conditions in which 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 otherwise instructed in test procedures, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance.
NOTE:
The following table provides the location of commonly use diagnostic information. These former "A" and "C" charts are now written in text and inserted into the appropriate location in the new Engine Performance workflow. To familiarize yourself with the Engine Performance workflow, see 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 | See DIAGNOSTIC CIRCUIT CHECK (DIESEL) or DIAGNOSTIC CIRCUIT CHECK (GASOLINE) | ||
| A-1 & A-2, SERVICE ENGINE SOON Light | See DIAGNOSTIC CIRCUIT CHECK (DIESEL) or DIAGNOSTIC CIRCUIT CHECK (GASOLINE) | ||
| A-3, No-Start | See NO-START DIAGNOSIS | ||
| A-5, Fuel Pump Relay | See RELAYS, SOLENOIDS, MOTORS & MODULES in SYSTEM/COMPONENT TESTS | ||
| A-6 & A-7, Fuel System Diagnosis | See BASIC FUEL SYSTEM CHECKS (DIESEL) or BASIC FUEL SYSTEM CHECKS (GASOLINE) | ||
| C-1, MAP Sensor | See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS | ||
| C-1, Power Steering Pressure Switch | See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS | ||
| C-1, Park/Neutral Switch | See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS | ||
| C-2, Injector Balance Test (4.3L) | See FUEL CONTROL in SYSTEM/COMPONENT TESTS | ||
| C-2, IAC Motor | See IDLE CONTROL SYSTEM in SYSTEM/COMPONENT TESTS | ||
| C-3, Canister Purge System | See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS | ||
| C-4, EST Ignition Check | See C-4, BASIC IGNITION SYSTEM CHECKS | ||
| C-5, ESC Ignition Check | See IGNITION SYSTEM in SYSTEM/COMPONENT TESTS | ||
| C-6, Air Injection System | See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS | ||
| C-7, EGR System | See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS | ||
| C-8, Torque Converter Clutch | See MISCELLANEOUS ECM CONTROLS in SYSTEM/COMPONENT TESTS | ||
| C-8, M/T Shift Lights | See MISCELLANEOUS ECM CONTROLS in SYSTEM/COMPONENT TESTS | ||
| C-10, A/C Clutch Control | See MISCELLANEOUS ECM CONTROLS In SYSTEM/COMPONENT TESTS | ||
| C-12, Electric Cooling Fan Control | (1) See MISCELLANEOUS ECM CONTROLS in SYSTEM/COMPONENT TESTS | ||
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