Engine Controls - Basic Testing: Introduction
The following diagnostic steps help prevent overlooking simple problems. This is also where to begin diagnosis for no-start condition.
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. Following table provides location of commonly used diagnostic information. These former "A" and "C" charts are now written in text and inserted into appropriate location of engine performance workflow.
GENERAL MOTORS "A" & "C" CHART REFERENCE
| System Or Component | Diagnostic Information Location | ||||
|---|---|---|---|---|---|
| DIAGNOSTIC CIRCUIT CHECK | See appropriate DIAGNOSTIC CIRCUIT CHECK | ||||
| A-1 & A-2, Malfunction Indicator Light (MIL) | See appropriate DIAGNOSTIC CIRCUIT CHECK or appropriate TESTS W/CODES article. | ||||
| A-3, No-Start | See A-3, NO-START DIAGNOSIS | ||||
| A-5, Fuel Pump Relay | See RELAYS, SOLENOIDS, MOTORS & MODULES in I - SYS/COMP TESTS article in this section | ||||
| A-6 & A-7, Fuel System Diagnosis | See appropriate BASIC FUEL SYSTEM CHECKS | ||||
| C-1, MAP Sensor | See ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS article in this section | ||||
| C-1, Power Steering Pressure Switch | See ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS article in this section | ||||
| C-1, Park/Neutral Switch | See ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS article in this section | ||||
| C-2, Injector Balance Test (4.3L) | See FUEL CONTROL under FUEL SYSTEM (GAS) in I - SYS/COMP TESTS article in this section | ||||
| C-2, IAC Motor | See IDLE CONTROL SYSTEM under FUEL SYSTEM (GAS) in I - SYS/COMP TESTS article in this section | ||||
| C-3, Canister Purge System | See appropriate EMISSION SYSTEMS & SUB-SYSTEMS in I - SYS/COMP TESTS article in this section. | ||||
| C-4, EST Ignition Check | See C-4, BASIC IGNITION SYSTEM CHECKS (GASOLINE) | ||||
| C-5, ESC Ignition Check | See IGNITION SYSTEM in I - SYS/COMP TESTS article in this section | ||||
| C-6, Air Injection System | See appropriate EMISSION SYSTEMS & SUB-SYSTEMS in I - SYS/COMP TESTS article in this section | ||||
| C-7, EGR System | See appropriate EMISSION SYSTEMS & SUB-SYSTEMS in I - SYS/COMP TESTS article in this section | ||||
| C-8, Torque Converter Clutch | (1) See MISCELLANEOUS ECM CONTROLS in I - SYS/COMP TESTS article in this section | ||||
| C-8, Manual Transmission Shift Lights | (1) See MISCELLANEOUS ECM CONTROLS in I - SYS/COMP TESTS article in this section | ||||
| C-10, A/C Clutch Control | See MISCELLANEOUS ECM CONTROLS in I - SYS/COMP TESTS article in this section | ||||
| C-12, Electric Cooling Fan Control | (2) See MISCELLANEOUS ECM CONTROLS in I - SYS/COMP TESTS article in this section | ||||
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