GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 2008 🢒 Unit Repair 🢒 Engine 🢒 Engine Controls and Fuel - LS Engines 🢒 Powertrain On Board Diagnostic (OBD) System Check
  1. Verify that none of the following preliminary inspections/tests reveal the cause of the vehicle concern before beginning diagnosis:
    2. • Ensure that the battery is fully charged.
    • Ensure that the battery cables are clean and tight.
    • Inspect for any open fuses. Refer to Engine Controls Schematics .
    • Ensure that the grounds are clean, tight, and in the correct location.
    • Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the concern. This would include checking to ensure that all connections/connectors are fully seated and secured.
    • Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories .
    • Search for applicable service bulletins.
    ⇒If the preceding inspections/tests resolve the concern, go to Diagnostic Repair Verification .
  2. Install a scan tool. Verify that the scan tool powers up.
    3. ⇒If the scan tool does not power up, refer to Scan Tool Does Not Power Up .
  3. Ignition ON, Engine OFF, verify communication with all of the control modules on the vehicle.
    4. ⇒If the scan tool does not communicate with one or more of the expected control modules, refer to Scan Tool Does Not Communicate with CAN Device .
  4. Attempt to start the engine. Verify that the engine cranks.
    5. ⇒If the engine does not crank, repair the starting system.
  5. Attempt to start the engine. Verify the engine starts and idles.
    6. ⇒If the engine does not start and idle, refer to Engine Cranks But Does Not Run .

    Important: Do not clear any DTCs unless instructed to do so by a diagnostic procedure.

  6. Use the appropriate scan tool selections to obtain DTCs from the vehicle module. Verify there are no DTCs reported from the control module.
    7. ⇒If any DTCs are present, refer to Diagnostic Trouble Code (DTC) List and diagnose any current DTCs in the following order:
    6.1. DTC 51.
    6.2. Component level DTCs.
    6.3. System level DTCs.
    6.4. Any remaining DTCs.
    ⇒If none of the previous tests or inspections addresses the concern, refer to Symptoms - Engine Controls .