GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC C Sierra - 2WD (CNG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 Diagnostic System Check - Alternative Fuels (Engine Controls)

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. A module that is operating in the incorrect power mode based on key position may cause other vehicle symptoms and/or DTCs to set. The link to "Power Mode Mismatch" will correct the condition before checking for module DTCs or symptoms.

    4.

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

    5.

  5. This step insures that all ECU internal DTCs are diagnosed before other system level DTCs.

    6.

  6. 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.
    • 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.
    • 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.
    • Ensure that the compressed natural gas (CNG) and gasoline fuel tanks are at least ½ full.

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 in the C/K Pickup Service Manual

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 in the C/K Pickup Service Manual 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 in the C/K Pickup Service Manual

4

Important: 

  1. To ensure that retained accessory power (RAP) mode is inactive (if equipped), open the drivers door during the following step.
  2. The engine may start during the following step. Turn OFF the engine as soon as you have observed the crank power mode.

  1. Access the Power Mode parameter on the scan tool.
  2. Rotate the ignition switch (operate the ignition mode switch) through all positions while observing the Power Mode parameter. Refer to Body Control System Description and Operation in Computer/Integrating Systems in the C/K Pickup Service Manual for a list of the power mode states that correspond with each switch position.

Does the Power Mode parameter reading on the scan tool match the ignition switch position for all switch positions?

Go to Step 5

Go to Power Mode Mismatch in Computer/Integrating Systems in the C/K Pickup Service Manual

5

Attempt to start the engine.

Does the engine crank?

Go to Step 6

Go to Symptoms - Engine Electrical in Engine Electrical in the C/K Pickup Service Manual

6

Attempt to start the engine.

Does the engine start and idle?

Go to Step 7

Go to DTC P1204

7

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

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

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 8

Go to Step 12

8

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

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information in the C/K Pickup Service Manual

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 B1000, B1004, B1007, B1009, C0550, P0601, P0602, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P2108, or P2610?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information in the C/K Pickup Service Manual

Go to Step 10

10

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

Does the scan tool display DTC B1372, B1420, P0562, or P0563?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information in the C/K Pickup Service Manual

Go to Step 11

11

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

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, evaporative emission (EVAP) system DTCs, and fuel trim DTCs.

Does the scan tool display DTC P0005, P0148, P0171, P0172, P0174, P0175, P0182, P0183, P0186, P0187, P0188, P0191, P0192, P0193, P0200, P0300, P0611, P1020, P1021-P1028, P1204, P1207, P1209, P1431, P1432, P1433, P2146, or P2665?

Go to Diagnostic Trouble Code (DTC) List

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information in the C/K Pickup Service Manual

12

Is the vehicle equipped with the dedicated CNG fuel option (KL8)?

Go to Step 14

Go to Step 13

13
  1. Start and idle the engine.
  2. Force a switch over to gasoline operation with the scan tool in the Alternative Fuels special functions, output controls menu.

Does the engine continue to idle?

Go to Step 14

Go to Engine Cranks But Does Not Run in Engine Controls in the C/K Pickup Service Manual

14

Is the customers concern with inspection/maintenance (I/M) testing?

Go to Inspection/Maintenance (I/M) System Check in Engine Controls - 4.8L, 5.3L, and 6.0L in the C/K Pickup Service Manual

Go to Step 15

15

Is the customers concern with a driveability symptom while operating on CNG fuel?

Go to Symptoms - Engine Controls

Go to Symptoms - Vehicle in Vehicle DTC Information in the C/K Pickup Service Manual