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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series Commercial (Cutaway) C4/C5 🢒 Preface 🢒 Cautions and Notices 🢒 Diagnostic System Check - Vehicle

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step insures that the battery, and the vehicle primary power and ground systems are functioning correctly.

    2.

  2. Lack of communication may be due to a particular malfunction of a serial data circuit. The link to "Scan Tool does not Communicate with Class 2 Device" will provide a list of modules and the associated data network no communication diagnostic link.

    3.

  3. This step insures that all data link communication DTCs are diagnosed before system level DTCs.

    4.

  4. This step insures that all electronic control unit (ECU) internal DTCs are diagnosed before other system level DTCs.

    5.

  5. This step insures that all device voltage DTCs are diagnosed before other system level DTCs.

Step

Action

Yes

No

1

Perform the following preliminary inspections:

    • Ensure that the battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.
    • Ensure that the battery cables are clean and tight.
    • Inspect for any open fuses. Refer to Power Distribution Schematics and Electrical Center Identification Views .
    • Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the symptom.
    • Ensure that the grounds are clean, tight, and in the correct location. Refer to Ground Distribution Schematics and Power and Grounding Component Views .
    • Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Search for applicable service bulletins.

Did you find and correct the condition?

System OK

Go to Step 2

2

Install a scan tool.

Does the scan tool power up?

Go to Step 3

Go to Scan Tool Does Not Power Up in Computer/Integrating Systems

3

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with all of the control modules on the vehicle. Refer to Scan Tool Does Not Communicate with Class 2 Device in Computer/Integrating Systems for the modules you should expect to observe.

Does the scan tool communicate with all of the expected vehicle control modules?

Go to Step 4

Go to Scan Tool Does Not Communicate with Class 2 Device in Computer/Integrating Systems

4

Attempt to start the engine.

Does the engine crank?

Go to Step 5

Go to Symptoms - Engine Electrical in Engine Electrical

5

Important: For the 7.2L Caterpillar Engine, refer to the appropriate Caterpillar Service Manual.

Attempt to start the engine.

Does the engine start and idle?

Go to Step 6

Go to:

    •  Engine Cranks But Does Not Run in Engine Controls - 6.6L(LLY)
    •  Engine Cranks But Does Not Run in Engine Controls - 7.8L
    •  Engine Cranks But Does Not Run in Engine Controls - 8.1L

6

Important: For the 7.2L Caterpillar Engine, refer to the appropriate Caterpillar Service Manual.

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

Use the appropriate scan tool selections to obtain DTCs for each of the control modules.

Does the scan tool display any DTCs?

Go to Step 7

Go to Symptoms - Vehicle

7

Does the scan tool display any DTCs that begin with a "U"?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 8

8

Important: If any of these DTCs are displayed, diagnose them before diagnosing any other DTCs or symptoms.

Does the scan tool display DTC B1000, B1001, C0550, P0601, P0602, P0603, P0604, P0605, P0606, P1621, P2107, P2108, or P2610?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 9

9

Important: If any of these DTCs are displayed, diagnose them before diagnosing any other DTCs or symptoms.

Does the scan tool display DTC B1372, C0899, C0900, P0562, or P0563?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 10

10

Important: If any of the remaining DTCs are powertrain DTCs, select Capture Info in order to store the powertrain DTC information with a scan tool.

If multiple DTCs are stored, diagnose the DTCs 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.

Diagnose the remaining DTCs.

Go to Diagnostic Trouble Code (DTC) List - Vehicle

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