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Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Classic - 4WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Scan Tool Does Not Communicate with High Speed GMLAN Device

Scan Tool Does Not Communicate with High Speed GMLAN Device Diesel

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

High speed GMLAN serial data bus (+)

1

2

1

--

High speed GMLAN serial data bus (-)

1

2

1

--

1. No communication on any high speed GMLAN module.

2. An open in only one high speed GMLAN serial data circuit may allow degraded communication between the modules or no communication with a specific module.

Circuit/System Description

Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The high speed GMLAN serial data bus uses two 120 ohm terminating resistors that are in parallel with the high speed GMLAN (+) and (-) circuits. One of the resistors is connected near the data link connector (DLC) end of the link and the other is internal to the ECM/PCM end of the link. The DLC terminating resistor is not internal to a module. Modules connected to the high speed GMLAN serial data circuits are the transmission control module (TCM), glow plug control module (GPCM), and the engine control module/powertrain control module (ECM/PCM).

Diagnostic Aids
    • Use the Data Link References to identify the high speed GMLAN serial data modules.
    • This test is used for a total high speed GMLAN communication failure. If only 1 module is not communicating and sets no DTC, ensure that the vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.
    • Use the DMM MIN/MAX function to capture/locate intermittent conditions.
    • 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
       - An open in a high speed GMLAN serial data circuit between the DLC and the first splice. This open will cause no communication with the scan tool, and will not effect the module communication on the vehicle.

Reference Information

Schematic Reference

    •  Data Communication Schematics
    •  Control Module References

Connector End View Reference

Master Electrical Component List

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Circuit/System Testing

Automatic Transmission

  1. Ignition OFF, disconnect the harness connector of the GPCM.
  2. Ignition ON, with a scan tool attempt to communicate with the ECM/PCM. Communication should not be available.
    3. ⇒If the ECM/PCM communicates, replace the GPCM.
  3. Disconnect the ECM/PCM. Ignition ON, with a scan tool attempt to communicate with the TCM. Communication should not be available.
    4. ⇒If the TCM communicates, replace the ECM/PCM.
  4. All 3 modules disconnected, test for less than 5 ohms of resistance between the DLC and the TCM on both high speed GMLAN serial data circuits.
    5. ⇒If greater than 5 ohms, repair the data circuit for open/high resistance between the DLC and the first splice.
  5. All 3 modules disconnected, test for infinite resistance between all 4 of the high speed GMLAN serial data (+) and (-) circuits of the TCM.
    6. ⇒If less than infinite resistance, repair the short between the serial data circuits.
  6. Ignition on and all 3 modules disconnected, test for less than 1.0 volt between the high speed GMLAN serial data circuits of the TCM and ground.
    7. ⇒If greater than 1.0 volt, repair the serial data circuit of the TCM for a short to voltage.
  7. All 3 modules disconnected, test for infinite resistance between the high speed GMLAN serial data circuits of the TCM and ground.
    8. ⇒If less than infinite resistance, repair the serial data circuits for a short to ground.
  8. If all circuits test normal, replace the TCM.

Manual Transmission

  1. Ignition OFF, disconnect the harness connector of the GPCM.
  2. Ignition ON, with a scan tool attempt to communicate with the ECM/PCM. Communication should not be available.
    3. ⇒If the ECM/PCM communicates, replace the GPCM.
  3. Test for less than 5 Ohms of resistance between the DLC and the ECM/PCM on both high speed GMLAN serial data circuits.
    4. ⇒If greater than 5 Ohms, repair the data circuit for open/high resistance between the DLC and the first splice.
  4. Both modules disconnected, test for infinite resistance between the high speed GMLAN serial data (+) and (-) circuits of the DLC.
    5. ⇒If less than infinite resistance, repair the short between the serial data circuits.
  5. Ignition on and both modules disconnected, test for less than 1.0 volt between the high speed GMLAN serial data circuits of the DLC and ground.
    6. ⇒If greater than 1.0 volt, repair the serial data circuit for a short to voltage.
  6. Both modules disconnected, test for infinite resistance between the high speed GMLAN serial data circuits of the DLC and ground.
    7. ⇒If less than infinite resistance, repair the serial data circuits for a short to ground.
  7. If all circuits test normal, replace the ECM/PCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Control Module References for module replacement, setup, and programming
    •  GMLAN Wiring Repairs

Scan Tool Does Not Communicate with High Speed GMLAN Device HP2

Circuit Description

Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications on the high speed GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules.

The scan tool communicates with the following modules via the high speed GMLAN:

    • Energy Storage Control Module (ESCM)
    • Starter/Generator Control Module (SGCM)
    • Electro-Hydraulic Power Steering (EHPS) Module

Diagnostic Aids

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

Step

Action

Yes

No

Schematic Reference: Data Communication Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

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

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:
    3. • 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:

    •  Circuit Testing
    •  Connector Repairs
    •  GMLAN Wiring Repairs

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 .

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 and Connector Repairs .

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

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

Go to Step 10

10

Use the scan tool in order to clear the DTCs.

Did you complete the action?

System OK

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