LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Pontiac >> 2003 >> Sunfire Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 2.2L >> Self-Diagnostic System >> Diagnostic System Check - Engine Controls >> Diagnostic Procedures
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedures

NOTE: DO NOT perform this test if no driveability condition exists. Search for applicable bulletins before proceeding with the diagnosis. DO NOT turn OFF ignition when performing this diagnostic test procedure. DO NOT clear the DTCs unless the diagnostic instructs you to do so. If there is a condition with the starter system, diagnose starter system. See appropriate STARTERS article in STARTING & CHARGING SYSTEMS. Ensure battery is fully charged and cables are clean and tight. Ensure PCM grounds are clean, tight, and in proper location.
  1. Install scan tool. Does scan tool power up? If yes, go to next step. If no, perform SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
    2. NOTE: If using a Tech 2 scan tool, obtain the information using the Class 2 Message Monitor feature.
  2. Turn ignition switch to RUN position, engine off. Using scan tool, attempt to establish communication with the Body Control Module (BCM), Electronic Brake Control Module (EBCM), Instrument Panel Cluster (IPC), Powertrain Control Module (PCM) and Sensing and Diagnostic Module (SDM). Does scan tool communicate with all the control modules? If yes, go to next step. If no, perform SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  3. Attempt to start engine. Does engine start and idle? If yes, go to next step. If no, go to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
  4. Using scan tool, select the DTC display function for the BCM, EBCM, BCM, PCM and SDM. Does scan tool display any DTCs? If yes, go to next step. If no, go to step  9.
  5. Using scan tool, select CAPTURED INFO to store the powertrain DTC information. When complete, go to next step.
  6. Does scan tool display DTCs which begin with a "U"? If yes, go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  7. Were any of PCM DTCs P0601, P0602 or P1621 set? If yes, go to DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683 OR P2610: ECU MALFUNCTION  under DIAGNOSTIC TESTS. If no, go to next step.
  8. Does scan tool display DTC P0562, P0563, P0621 or P0622? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  9. Is customer's concern with the automatic transmission? If yes, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If no, go to next step.
  10. Is customer's concern with the Inspection/Maintenance (I/M) testing? If yes, go to INSPECTION/MAINTENANCE SYSTEM CHECK  under DRIVE CYCLES. If no, go to next step.
  11. Check for the following symptoms:
    • Hard start.
    • Surges/chuggles.
    • Lack of power, sluggishness, or sponginess.
    • Detonation/spark knock.
    • Hesitation, sag, stumble.
    • Cuts out/misses.
    • Poor fuel economy.
    • Rough, unstable, or incorrect idle and stalling.
    • Dieseling/run-on.
    • Backfire.
    • MIL inoperative. For repair, see MIL INOPERATIVE  under SYSTEM TESTS.
    • MIL always on. For repair, see MIL ALWAYS ON  under SYSTEM TESTS.
    Repair as necessary. If no problem is found, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.
scientia non olet · About LEMON Manuals