Computer/integrating Systems: Overview Chevrolet Uplander I

Computer/Integrating Systems 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 ZONES . Failure to observe the correct procedure could cause deployment of the SIR components, personal injury or unnecessary SIR system repairs

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Computer/Integrating Systems Connector End Views

Body Control Module (BCM) C1

Test Description

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

1. 3: If DTC B1001 is set as current, reprogram the module.

DTC B1001

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

1. 3: This step tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the ignition 1 circuit in the OFF position.
2. 4: This step tests the wiring of the ignition 1 circuit for a short to ground or voltage.
3. 5: This step tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the ignition 1 circuit in the Run and Crank switch positions. Care must be taken as the engine may crank during this test.

DTC B1370

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

1. 3: This step tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the ignition 3 circuit in the OFF position.
2. 4: This step tests the wiring of the ignition 3 circuit for a short to ground or voltage.
3. 5: This step tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the ignition 3 circuit in the Run and Crank switch positions. Care must be taken as the engine may crank during this test.

DTC B1380

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

1. 3: This step tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the crank circuit in the OFF position.
2. 4: This step tests the wiring of the crank circuit for a short to ground or voltage.
3. 5: This step tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the crank circuit in the Crank switch position. Care must be taken as the engine may crank during this test.

DTC B1385

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

1. 2: Listen for an audible click when the IGN 1 relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.
2. 3: This step verifies that the BCM is providing voltage to the IGN 1 relay.
3. 4: This step tests for an open in the ground circuit to the IGN 1 relay.
4. 5: This step tests if voltage is constantly being applied to the IGN 1 relay.

DTC B1428

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

1. 2: Listen for an audible click when the RUN relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3: This step tests for voltage at the coil side of the RUN relay.
3. 4: This step verifies that the BCM is providing ground to the RUN relay.
4. 5: This step tests the control circuit side of the RUN relay for faults.
5. 10: After replacement of the BCM you must calibrate the new module for proper operation.

DTC B1433

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

1. 2: Listen for an audible click when the RAP relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.
2. 3: This step tests for voltage at the coil side of the RAP relay. The RAP fuse supplies power to the coil side of the RAP relay.
3. 4: This step verifies that the BCM is providing ground to the RAP relay.
4. 5: This step tests the control circuit side of the RAP relay for faults that cause both B1475 RAP DTC.
5. 10: After replacement of the BCM you must calibrate the new module for proper operation.

DTC B1475

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

1. 1: A Lost Communication with XXX DTC with a history status may indicate the cause of U1000.
2. 2: The module that is not communicating is the likely cause of U1000 or U1255 being set.
3. 5: The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
4. 6: The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
5. 7: The module that was not communicating may have set Lost Communication with XXX DTCs for those modules that the module was monitoring.
6. 11: The modules that communicate indicate the module that cannot communicate. You must clear the DTC from the modules in order to avoid future misdiagnosis.
7. 13: If all modules are communicating, the module that set U1000 may have done so due to some other condition.
8. 14: The module that set U1000 is the likely cause of the malfunction.

DTC U1000 and U1255

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

1. 1: A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.
2. 2: A module which loses ground during an ignition cycle will cause other modules to set Lost Communication DTCs.
3. 3: The malfunction is due to an open in the class 2 serial data circuit or an open in the module.
4. 7: The module which was not communicating may have set Lost Communication DTCs for those modules that it was monitoring.
5. 9: The modules which can communicate indicate the module which cannot communicate. You must clear the DTCs from these modules to avoid future misdiagnosis.

DTC U1001-U1254

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 loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
2. 4: The following DTCs may be retrieved with a history status. These DTCs 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 with a current status. This indicates that the malfunction occurred when the ignition was ON.
4. 10: Normal class 2 serial data communication cannot take place until the power mode master (PMM) module sends the appropriate power mode message. If the PMM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
5. 12: This step uses the loss of communications with a class 2 serial data circuit to locate the probable malfunction. On vehicles equipped with a digital radio receiver (DRR), the DRR must be isolated from the sensing and diagnostic module (SDM) to evaluate the condition of that class 2 serial data circuit branch. The following modules communicate on the class 2 serial data circuit: Driver information center (DIC) DRR Electronic brake control module (EBCM) Instrument panel cluster (IPC) Head-up display (HUD) HVAC Powertrain control module (PCM) Radio Vehicle communication interface module (VCIM) SDM
6. 17: If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.
7. 18: The communication concern may have prevented diagnosis of the customer complaint.

Scan Tool Does Not Communicate with Class 2 Device

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

1. 6: This step tests for battery voltage on the incorrect signal circuits.
2. 7: This step tests for no battery voltage on the required signal circuits.
3. 8: If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
4. 9: This step eliminates open circuits as the cause of the malfunction.

Power Mode Mismatch

Body Control System Description and Operation

The body control system consists of the body control module (BCM) and its associated controls. Battery positive voltage is provided to the BCM from the TURN/HAZ fuse and the CHMSL/BKUP fuse in the fuse block instrument panel (I/P). The module grounds are wired to ground G200, G201 and G301. The BCM is wired to the class 2 serial data communication bus as well as discrete input and output terminals to control the functions of the vehicles body.

Power Mode Description and Operation

Power to many of this vehicle's circuits are controlled by the module that is designated the Power Mode Master (PMM). This vehicle's PMM is the Body Control Module (BCM). The PMM controls which power mode (Run, Accessory, Crank, Retained Accessory Power or Off) is active.

See also:
• Master Electrical Component List