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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 663 (COMPUTER/INTEGRATING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH HIGH SPEED GMLAN DEVICEDIAGNOSTIC AIDS
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Diagnostic Aids

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Diagnostic Aids
WARNING: This page is about a different car, the 2006 GMC Sierra, 2006 GMC Cab & Chassis Sierra, 2006 Chevrolet Silverado, and 2006 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: The tool communication with the modules connected only to high speed GMLAN data link requires the use of the CANdi module. Due to configuration of this vehicle, they may be communication DTCs set against modules that are able to communicate with the scan tool.

The following conditions may cause a total loss of high speed GMLAN data communication:

  • A short between high speed GMLAN (+) and high speed GMLAN (-) circuits
  • Any of the high speed GMLAN serial data circuits shorted to ground or voltage
  • A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits
Scan Tool Does Not Communicate with High Speed GMLAN Device

Step Action Yes No
Schematic Reference: Data Link Connector (DLC) Schematics 
Connector End View Reference: Master Electrical Component List in Wiring Systems
1 Did you perform the Diagnostic System Check - Vehicle? Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
  1. Turn ON the ignition, with the engine OFF.
  2. Retrieve DTCs from the powertrain control module (PCM).
Did you record any DTCs in the range of U1881 to U1899?		 Go to DTC U1881-U1899  Go to Step 3 
3 Did you record any DTCs in the range of U0100 to U0299? Go to DTC U0100-U0299 (Diesel Engine)  or DTC U0100-U0299 (HP2)  Go to Step 4 
4 Attempt to communicate with the following modules:
  • Energy storage control module (ESCM)
  • Starter/Generator control module (SGCM)
  • Electro-hydraulic power steering (EHPS)

Does the scan tool communicate with all listed modules?		 Go to Step 5  Go to Step 6 
5
IMPORTANT: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.
  1. Disconnect the scan tool from the data link connector (DLC).
  2. Test the high speed GMLAN serial data circuits for:
    • an intermittent short to ground
    • an intermittent short to voltage
    • an intermittent short between high speed GMLAN (+) and (-) circuits
    • an intermittent open on any of the circuits
Refer to the following in Wiring Systems:Did you find and correct the condition?		 Go to Step 10  Go to Diagnostic Aids
6
  1. Turn OFF the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections at the DLC terminals 6 and 14. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 8  Go to Step 7 
7
  1. Disconnect the SGCM.
  2. Repair the high speed GMLAN serial data circuits between DLC connector and SGCM for an open. Refer to GMLAN Wiring Repairs andConnector Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 8  -
8
  1. Reconnect all of the disconnected modules.
  2. Install a scan tool.
  3. Turn ON the ignition, with the engine OFF.
  4. Select the Display DTCs function for each module.
  5. Record all of the displayed DTCs and the DTC status.
Did you record any DTCs which begin with a "U" and with a current status?		 Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information Go to Step 9 
9 Did you record any DTCs which do not begin with a "U"? Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information Go to Step 10 
10 Use the scan tool in order to clear the DTCs.
Did you complete the action?		 System OK -
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.