Data Communication System: Overview Chevrolet Silverado Classic 2500 HD

Data Communication Schematic Icons

Data Communication Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR DISABLING AND ENABLING . Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs. IMPORTANT: Twisted-pair wires provide an effective shield that helps protect sensitive electronic components from electrical interference. In order to prevent electrical interference from degrading the performance of the connected components, you must maintain the proper specification when making any repairs to the twisted-pair wires shown : The wires must be twisted a minimum of 9 turns per 31 cm (12 in) as measured anywhere along the length of the wires. The outside diameter of the twisted wires must not exceed 6.0 mm (0.25 in)

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Body Control Module (BCM) - C1 Connector & Terminal Parts Information

Body Control Module (BCM) - C1 Terminal Identification

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Body Control Module (BCM) - C2 Connector & Terminal Parts Information

Body Control Module (BCM) - C2 Terminal Identification

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Body Control Module (BCM) - C3 Connector & Terminal Parts Information

Body Control Module (BCM) - C3 Terminal Identification

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Body Control Module (BCM) - C4 Connector & Terminal Parts Information

Body Control Module (BCM) - C4 Terminal Identification

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Body Control Module (BCM) - C5 Connector & Terminal Parts Information

Body Control Module (BCM) - C5 Terminal Identification

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Body Control Module (BCM) - C6 Connector & Terminal Parts Information

Body Control Module (BCM) - C6 Terminal Identification

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Data Link Connector (DLC) Connector & Terminal Parts Information

Data Link Connector (DLC) Terminal Identification

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Splice Pack SP205 Connector & Terminal Parts Information

Splice Pack SP205 Terminal Identification

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Splice Pack SP207 (w/o Y91) Connector & Terminal Parts Information

Splice Pack SP207 (w/o Y91) Terminal Identification

Test Description

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

1. 2: A total loss of communication on high speed GMLAN serial data link should be diagnosed first.
2. 10: The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.

DTC U0100-U0299 (Diesel Engine)

The number below refers to the step number on the diagnostic table.

1. 11: A resistance out of range will indicate one of several specific faults as follows: A high resistance indicates an open or high resistance in either of the high speed GMLAN serial data circuits between C 206 and the modules, including all module internals, circuits between, and module terminal tension. A low resistance indicates a short between the high speed GMLAN serial data circuits, including module internals. Infinite resistance indicates an open between the DLC and C 206 in either of the high speed GMLAN serial data circuits.

DTC U0100-U0299 (HP2)

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

1. 2: A DTC U1001-U1254 Lost Communications with XXX with a history status may indicate the cause of U1000.
2. 3: The modules not communicating are the likely cause of U1000. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
3. 7: The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001-U1254 Lost Communications with XXX for those modules that it was monitoring.
4. 10: The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
5. 13: If all modules are communicating, the module which set U1000 may have done so due to some other condition.
6. 15: The module which set U1000 is the likely cause of the malfunction.

DTC U1000

The number below refers to the step number on the diagnostic table.

1. 7: The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.

DTC U1001-U1254

The number below refers to the step number on the diagnostic table.

1. 4: The hydraulic motor EHPS 42 V battery voltage circuit includes a 125 A EHPS fuse inline, which is part of the 42-volt harness, below the starter/generator control module next to C121.
2. 9: The module which was not communicating may have set Loss of Communication DTCs for those modules that it was monitoring.

DTC U1881-U1899

Symptoms - Data Communications

1. Perform the «Diagnostic System Check - Vehicle»(ref-277883-S07139257572008012100000) , before using the symptom tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data links.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to: «Data Link Communications Description and Operation»(ref-277861-S38191002412008012100000) «Body Control System Description and Operation»(ref-277861-S39953004382008012100000)

The number below refers to the step number on the diagnostic table.

1. 4: If the battery positive voltage and ground circuits of the DLC are functioning properly, the malfunction must be due to the scan tool.

Scan Tool Does Not Power Up

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

1. 2: A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on the class 2 serial data circuit: The audio amplifier (AMP), w/UQ7 and Y91 The body control module (BCM) The communication interface module (OnStar®), w/UE1 The digital radio receiver (DRR), w/U2K The driver door module (DDM) The electronic brake control module (EBCM) The generator battery control module (GBCM) The HVAC control module The hybrid control module (HCM), w/HP2 The inflatable restraint sensing and diagnostic module (SDM) The instrument panel cluster (IPC) The memory seat module (MSM), w/AN3 The passenger door module (PDM) The powertrain/engine control module (PCM/ECM) The radio The rear seat audio (RSA) controller, w/UK6 The rear seat entertainment (RSE) assembly w/U42 The rear wheel steering control module (RWSCM), w/NYS The remote playback device - CD player (CDX), w/U1S The transfer case shift control module (TCSCM), w/NP1/NP8 The transmission control module (TCM), w/M74
2. 3: The following DTCs may be retrieved with a history status, but are not the cause of the present condition. U1300 U1301 U1305
3. 6: A state of health DTC with a history status may be present along with a U1000 or U1255 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
4. 7: Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
5. 10: A poor connection at DLC terminal of the splice pack SP205 would cause this condition but will not set a DTC.
6. 11: An open or a short in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
7. 13: This test isolates the BCM class 2 serial data circuits.
8. 16: The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the splice pack SP207 serial data circuits.
9. 21: This test isolates the rest of the splice pack SP205 serial data circuits.
10. 25: If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
11. 26: The communication malfunction may have prevented diagnosis of the customer complaint.

Scan Tool Does Not Communicate with Class 2 Device

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).

See also:
• Master Electrical Component List