GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Cobalt 🢒 Power and Signal Distribution 🢒 Data Communications 🢒 Diagnostic System Check - Vehicle
  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. Refer to Battery Inspection/Test .
    • Ensure that the battery cables are clean and tight.
    • Inspect for any open fuses. Refer to Power Distribution Schematics and Electrical Center Identification Views .
    • Ensure that the grounds are clean, tight, and in the correct location. Refer to Ground Distribution Schematics and Harness Routing Views .
    • 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. Refer to Data Link References for information on the modules you should expect to communicate.
    4. ⇒If the scan tool does not communicate with one or more of the expected control modules, refer to Data Link References .

    Important: Open the drivers door to ensure retained accessory power mode (RAP) is inactive during this test. The engine may start during this test. Turn the engine OFF as soon as the crank power mode has been observed.

  4. With a scan tool, access the body control module power mode data display list. Operate the ignition switch through all positions while observing the power mode data parameters.

    5. Verify that all the power mode parameters displayed correspond to the ignition key positions. Refer to Power Mode Description and Operation for information on the power mode states that correspond to each ignition switch position.

    ⇒If any of the power mode parameters do not match in any ignition switch position, refer to Power Mode Mismatch .
  5. Ignition ON, view the security indicator. The security indicator should not remain illuminated after the vehicle bulb check has completed.
    6. ⇒If the security indicator remains illuminated after the bulb check, refer to Diagnostic Trouble Code (DTC) List - Vehicle and diagnose any of the following theft deterrent DTCs set as current:
    ⇒B1000, B302A, B3031, B3055, B3060, B3935, B3976, P0513, P0633, P1629, P1631, or P1632.
  6. Attempt to start the engine. Verify that the engine cranks.
    7. ⇒If the engine does not crank, refer to Symptoms - Engine Electrical .
  7. Attempt to start the engine. Verify the engine starts and runs.
    8. ⇒If the engine does not start and run, refer to one of the following:
    •  Engine Cranks But Does Not Run for the 2.0L engine
    •  Engine Cranks But Does Not Run for the 2.2L (L61) engine
    •  Engine Cranks But Does Not Run for the 2.4L engine

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

    Important: If any DTCs are Powertrain related DTCs, select Capture Info in order to store the DTC information with the scan tool. If multiple Powertrain DTCs are stored, diagnose them in the following order:

    1. Component level DTCs; such as sensor DTCs, solenoid DTCs, and relay DTCs.

    2. System level DTCs; such as misfire DTCs, EVAP system DTCs, and fuel trim DTCs.

  8. Advance to the List All DTCs screen on the scan tool selections to obtain DTCs from each of the vehicle modules. Verify there are no DTCs reported from any module.
    9. ⇒If any DTCs are present, refer to Diagnostic Trouble Code (DTC) List - Vehicle and diagnose any current DTCs in the order the DTCs are displayed on the scan tool.
  9. If the customer concern is related to inspection/maintenance (I/M) testing, refer to one of the following:
    10. •  Inspection/Maintenance (I/M) System Check for the 2.0L engine
    •  Inspection/Maintenance (I/M) System Check for the 2.2L (L61) engine
    •  Inspection/Maintenance (I/M) System Check for the 2.4L engine
    ⇒If none of the previous tests or inspections addresses the concern, refer to Symptoms - Vehicle .