Sierra 3500 2WD V8-6.0L (2008)
communication between the high and low speed serial data busses. The low speed GMLAN serial data circuit must also be operational for vehicle
starting.
Diagnostic Aids
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Use the Data Link References to identify the high speed GMLAN serial data modules.
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This test is used for a total high speed GMLAN communication failure. If only one module is not communicating and sets no DTC, ensure that the
vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.
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An open in the DLC ground circuit terminal 5 will allow the scan tool to operate to set up the vehicle on the tool and then not communicate with
the vehicle. When the scan tool is to the point of communicating with the vehicle, a message on the scan tool will indicate "no CANdi module
detected" and will not communicate.
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The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus.
The following conditions may cause a total loss of high speed GMLAN data communication:
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A short between high speed GMLAN (+) and high speed GMLAN (-) circuits
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Any of the high speed GMLAN serial data circuits shorted to ground or voltage
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A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits
Circuit/System Testing
1. Test for less than 1 ohm between the DLC ground circuit terminal 5 and ground.
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If greater than 1 ohm, test the ground circuit for open/high resistance.
2. Ignition OFF, disconnect the harness connector of the BCM.
3. Ignition ON, test for B+ between each voltage input circuit of the BCM and ground.
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If less than specified, test each voltage output circuit of the BCM for a short to ground, and each voltage input circuit of the BCM for a short to
ground or and open/high resistance. If the circuits test normal, replace the faulty module.
4. Test for less than 1 ohm between each ground circuit of the BCM and ground.
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If greater than the specified range, repair the ground circuit for an open/high resistance.
5. Attempt to communicate with the electronic brake control module (EBCM). Communication should not be available.
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If communication is established, test or replace the resistor.
6. Ignition OFF, disconnect the harness connector of the suspension control module.
7. Attempt to communicate with the EBCM. Communication should not be available.
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If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the
suspension control module and the terminator resistor. If the circuits test normal, replace the suspension control module.
8. Ignition OFF, disconnect the harness connector of the distance sensing cruise control module.
9. Attempt to communicate with the EBCM. Communication should not be available.
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If communication is established, replace the cruise control module.
10. Ignition OFF, disconnect the harness connector of the vehicle communication interface module (VCIM).
11. Attempt to communicate with the EBCM. Communication should not be available.
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If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the between
the VCIM and the suspension control module. If the circuits test normal, replace the VCIM.
12. Ignition OFF, disconnect harness connector C3 of the BCM.
13. Test for infinite resistance between the serial data circuits of BCM harness connector C3 terminal 8 and ground and between BCM harness
connector C3 terminal 9 and ground.
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If less than the specified range, test the circuit for a short to ground.
14. Ignition OFF, disconnect the harness connector of the ECM. Connect harness connector C3 of the BCM.
15. Attempt to communicate with the EBCM. Communication should not be available.
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If communication is established, replace the ECM.
