2003 Hummer H2FACTORY OEM SERVICE PROCEDURE

Engine Electrical Diagnostic System Check

  1. Perform battery inspection test. See BATTERY TESTING & INSPECTION  under ON-VEHICLE TESTING. Go to next step.
  2. Connect scan tool to Data Link Connector (DLC). DLC is located below left side of instrument panel. Turn ignition switch RUN position. If scan tool powers up, go to next step. If scan tool does not power up, perform appropriate test. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  3. Turn ignition switch to RUN position with each module on class 2 serial data circuit. If scan tool communicates with modules, go to next step. If scan tool does not communicate with any module, perform appropriate test. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  4. Using scan tool, select DISPLAY DTCs function for each module on scan tool. Record all DTCs displayed, DTC status and module which set DTC. If scan tool displayed DTCs, go to next step. If scan tool did not display DTCs, repair charging system by symptom. See SYMPTOM INDEX  table under SYSTEM TESTS.
  5. If scan tool displays DTCs which begin with "U", perform appropriate test in accordance with DTC retrieved. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not display DTCs which begin with "U", go to next step.
  6. If scan tool does not display any DTCs which begin with "P", go to next step. If scan tool displays any DTCs which begin with "P", perform appropriate test in accordance with DTC retrieved. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  7. If scan tool displays DTCs which begin with "B", perform appropriate test in accordance with DTC retrieved. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not display DTCs which begin with "B", perform appropriate test in accordance with DTCs retrieved. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  .
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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.

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