GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls - 6.6L (LB7) 🢒 Diagnostic System Check - Instrument Cluster

Test Description

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

  1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

    2.

  2. The symptom list in Symptoms will determine the correct diagnostic procedure to use.

    3.

  3. The presence of DTCs which begin with "U" indicate that loss of class 2 communications has occurred.

Step

Action

Yes

No

1

Install a scan tool.

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up in Data Link Communications

2

  1. Turn the ignition ON, with the engine OFF.
  2. Attempt to establish communication with the following control modules:
    3. • Engine Control Module (ECM) - LB7, LLY and LG4
    • Hydraulic 4WAL 4 Sensor
    • Instrument Panel Cluster (IPC)
    • Powertrain Control Module (PCM) - L18
    • Serial Data Gateway
    • Supplemental Inflatable Restraint (SIR)
    • Transmission Control Module (TCM)

Does the scan tool communicate with the control modules listed above?

Go to Step 3

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

3

Select the display DTC function on the scan tool for the following control modules:

    • Engine Control Module (ECM) - LB7, LLY and LG4
    • Hydraulic 4WAL 4 Sensor
    • Instrument Panel Cluster (IPC)
    • Powertrain Control Module (PCM) - L18
    • Serial Data Gateway
    • Supplemental Inflatable Restraint (SIR)
    • Transmission Control Module (TCM)

Does the scan tool display any DTCs?

Go to Step 4

Go to Symptoms - Instrument Panel, Gages and Console

4

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

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

Go to Step 5

5

Does the scan tool display DTC B1000?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 6

6

Does the scan tool display DTC B1325, P0562, P0563, P0621, P0622, P1637 or P1638?

Go to Diagnostic Trouble Code (DTC) List in Engine Electrical

Go to Diagnostic Trouble Code (DTC) List