2003 Hummer H2FACTORY OEM SERVICE PROCEDURE

Diagnostic System Check - Engine Electrical: Notes

  1. Did you perform the Battery Inspection/Test? If yes, go to next step. If no, go to BATTERY INSPECTION/TEST (NON-HP2) .
  2. Install a scan tool. Does the scan tool power up? If yes, go to step  4. If no, go to SCAN TOOL DOES NOT POWER UP .
    3. NOTE: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.
  3. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter. Does the ignition switch parameter reading match the ignition switch position for all switch positions? If yes, go to next step. If no, go to POWER MODE MISMATCH .
  4. Turn ON the ignition, with the engine OFF. Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature. Does the scan tool communicate with any module on the class 2 serial data circuit? If yes, go to next step. If no, go to Scan Tool Does Not Communicate with Class 2 Device in BODY CONTROL MODULES
  5. Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules have DTCs set. Record all of the displayed DTCs the DTC status and the module which set the DTC. Does the scan tool display any DTCs? If yes, go to next step. If no, go to SYMPTOMS - ENGINE ELECTRICAL .
  6. Does the scan tool display any DTC beginning with "U"? If yes, go to Diagnostic Trouble Code (DTC) List . If no, go to next step.
  7. Does the scan tool display any DTC beginning with "P"? If yes, go to Powertrain DTC list in Engine Controls . If no, go to next step.
  8. Does the scan tool display any DTC beginning with "B"? If yes, go to Diagnostic Trouble Code (DTC) List .
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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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