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HOMESERVICE MANUALSCHEVROLET2000CAVALIER BASE, 2D COUPE, AUTOMATIC, 4T40E/MN4REPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L & 2.4LSELF-DIAGNOSTIC SYSTEMON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
2000 Chevrolet Cavalier Base, 2D Coupe, Automatic, 4T40E/MN4

On-Board Diagnostic (OBD) System Check

2000 Chevrolet Cavalier Base, 2D Coupe, Automatic, 4T40E/MN4SECTION On-Board Diagnostic (OBD) System Check
NOTE: Tech 1 or Tech 2 scan tool is required to perform OBD system check.

The OBD system check determines:

  • If Malfunction Indicator Light (MIL) operates.
  • If PCM is operating and can recognize a fault.
  • If any DTCs are stored.

After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the OBD system check, if no codes are indicated and driveability problems still exist, see appropriate TROUBLE SHOOTING - NO CODES article and SCAN TOOL USAGE  .

NOTE: Check for applicable Technical Service Bulletins (TSBs) before proceeding. DO NOT perform the following procedure if driveability conditions are not present. DO NOT turn ignition off during the following procedure or clear DTCs unless instructed to do so.
  1. Connect scan tool. Turn ignition on, with engine off. If scan tool powers up, go to next step. If scan tool does not power up, go to DLC DIAGNOSIS OR NO SCAN TOOL DATA  .
  2. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to DLC DIAGNOSIS OR NO SCAN TOOL DATA  .
  3. Using scan tool, check for DTCs. If any LAST TEST FAIL, HISTORY or MIL request DTCs are present, go to next step. If no DTCs are present, go to step  5 .
  4. Using scan tool, record FREEZE FRAME and FAILURE RECORDS information. Identify DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . After identification, diagnose DTCs. See DIAGNOSTIC TESTS.
  5. Observe MIL. If MIL is illuminated, go to next step. If MIL is not illuminated, go to MIL INOPERATIVE  .
  6. Using scan tool, command MIL off. If MIL turns off, go to next step. If MIL does not turn off, go to MIL ON STEADY  .
  7. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and then stalls, go to NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
  8. Allow engine to idle. During engine warm-up, check ECT, TP, MAP, O2 sensors and IAC valve for proper operation. Compare actual scan tool data with typical scan tool data values. If values are within limits, see appropriate TROUBLE SHOOTING - NO CODES article. If values are not within limits, go to appropriate SYSTEM & COMPONENT TESTING 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.