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Data Link Communications System Cadillac Escalade GMT400

Communication Devices 22 illustrations ~5142 words

DESCRIPTION & OPERATION

WARNINGVehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in AIR BAG RESTRAINT SYSTEMS article.
CAUTIONWhen battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

The Data Link Connector (DLC) is used as an access point for different vehicle diagnostic and programming functions involving the use of a scan tool.

UART DATA LINE

The UART serial data communication relies on a 5-volt digital signal for the exchange of data between different control modules and a scan tool. When the ignition is in RUN and there is no data transmission, there is a constant 5 volts on the data line. Communication on the line brings the voltage to zero volts. The supplemental restraint Sensing and Diagnostic Module (SDM) communicates on the UART data line.

CLASS 2 DATA LINE

Modules on the class 2 data line transmit state of health messages every two seconds to indicate proper functioning to other modules on the data line. Some modules recognize when other modules are not communicating. A Diagnostic Trouble Code (DTC) may be stored by a module that detects 5 seconds of non-communication from another module. Data line DTCs begin with the letter "U" and may be caused by faulty data line wiring, faulty module power or ground, or a faulty control module.

ENTERTAINMENT & COMFORT BUS

The entertainment and comfort bus allows the radio receiver to communicate with a scan tool when connected to the DLC.

REMOTE CONTROL DOOR LOCK RECEIVER PROGRAMMING

The remote control door lock receiver may be programmed by a scan tool when connected to the DLC.

SELECTABLE TRANSFER CASE CONTROL MODULE

The selectable Transfer Case Control Module (TCCM) has limited self-diagnostic capabilities and may be accessed by a scan tool when connected to the DLC.

COMPONENT LOCATIONS

ComponentLocation (Fig. No.)
Data Link ConnectorUnder Driver Side Of Instrument Panel Mounted To Bottom Of Knee Bolster (Scheme 1)
Electric Brake Control ModuleNear Master Brake Cylinder At Driver Front Wheel House (Scheme 2)
Electronic Variable Orifice/Passlock™ ModuleUnder Center Of Instrument Panel (Scheme 3)
Inflatable Restraint Sensing & Diagnostic Module (SDM)Under Driver Seat (Scheme 4)
Instrument Panel Fuse BlockLower Driver Side Of Instrument Panel (Scheme 5)
Powertrain Control ModuleUnder Passenger Side Of Instrument Panel (Scheme 6)
RadioCenter Of Instrument Panel (Scheme 7)
Remote Control Door Lock ReceiverUnder Center Of Instrument Panel, Right Of Knee Bolster (Scheme 8)
Transfer Case Control Module (A/T 4WD)Under Driver Side Of Instrument Panel Near Convenience Center (Scheme 9)
Transfer Case Shift Control ModuleUnder Driver Side Of Instrument Panel Near Convenience Center (Scheme 10)
Vehicle Control ModuleEngine Compartment, Near ECBM (Scheme 2)
C100Driver Rear Of Engine Compartment At Bulkhead (Scheme 5)
C200Behind Passenger Side Of Instrument Panel, In Foam Wrap ( (Scheme 11) or (Scheme 12) )
C231Instrument Panel Harness To Inflatable Restraint Harness (Scheme 13)
C239 (Luxury Models)Instrument Panel Harness Inline To Crossbody Harness, Next To C230
C298Behind Driver Side Of Instrument Panel, Near Convenience Center ( (Scheme 10) & (Scheme 13) )
G103 (Gasoline Engine)Top Front Center Of Engine, Near Thermostat Housing (Scheme 14)
G104 (5.0L/5.7L)Rear Side Of Passenger Cylinder Head (Scheme 15)
G104 (6.5L Diesel)Top Rear Side Of Passenger Cylinder Head (Scheme 16)
G104 (7.4L)Rear Side Of Engine Block, Below Passenger Cylinder Head (Scheme 14)
G200Behind Driver Side Of Instrument Panel, On Tie Bar Below Fuse Block (Scheme 5)
S150Engine Harness, Near EBCM Breakout
S204Instrument Panel Harness, Near C100 Towards DLC
S215Instrument Panel Harness, Near Instrument Cluster Breakout Towards Radio Connectors
S272Instrument Panel Harness, Near Auxiliary Power Outlet Breakout
S280Instrument Panel Harness, Near DLC Breakout

COMPONENT LOCATIONS

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PRELIMINARY INSPECTION

Verify customer complaint by operating suspected system. Visually inspect for obvious signs of mechanical and electrical damage. Inspect for blown fuses and damaged relays. Inspect for loose or corroded connections, damaged wiring harnesses and/or switches. Check for a broken or partially broken wire inside insulation, which could cause system malfunction but prove good in a continuity/voltage check with system disconnected. Ensure any aftermarket electronic equipment is properly installed. If fault is found, repair as necessary. If no fault is found, perform self-diagnostics. See SELF-DIAGNOSTIC SYSTEM .

RETRIEVING & CLEARING DTCS

Connect scan tool to Data Link Connector (DLC). To retrieve DTCs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK .

DIAGNOSTIC SYSTEM CHECK

The diagnostic system check determines

  1. If Malfunction Indicator Light (MIL) operates.
  2. If PCM is operating and can recognize a fault.
  3. If any DTCs are stored.
  1. Using scan tool, attempt to make contact with any of the modules on the vehicle. If the main menu appears on the scan tool, go to next step. If the screen is blank or there is no power to the scan tool, see «SCAN TOOL INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__scan-tool-inoperative) under SYSTEM TESTS.
  2. Select "diagnostics circuit check, class 2 DTC check" on the main menu. The scan tool should list the PCM/VCM, ABS/TCS, VTD/EVO and ATCM (if the vehicle has an automatic transfer case). If the scan tool lists all modules, go to next step. If some or all of the modules are not listed, see «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DATA LINE»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__scan-tool-does-not-communicate-with) under SYSTEM TESTS.
  3. Select "body diagnostics" on the scan tools menu. Select "SIR UART data line information". Access any DTCs that may be present. If no DTCs are present, go to next step. If any DTCs are present, diagnose as necessary. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-trouble-code-definitions) . If there is no communication with the scan tool, see «SCAN TOOL DOES NOT COMMUNICATE WITH UART DATA LINE»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__scan-tool-does-not-communicate-with) under SYSTEM TESTS.
  4. Select "body diagnostics" on the scan tools menu. Select "E and C data line" and access any DTCs that may be present. If no DTCs are present, go to next step. If any DTCs are present, diagnose as necessary. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-trouble-code-definitions) . If there is no communication with the scan tool, see «SCAN TOOL DOES NOT COMMUNICATE WITH ENTERTAINMENT & COMFORT DATA LINE»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__scan-tool-does-not-communicate-with) under SYSTEM TESTS.
  5. Establish communication with the EBCM. If the vehicle is 15,000 GVW or more, access any DTCs that may be present. If no DTCs are present, go to next step. If any DTCs are present, diagnose as necessary. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-trouble-code-definitions) . If there is no communication with the scan tool, see «SCAN TOOL DOES NOT COMMUNICATE WITH EBCM»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__scan-tool-does-not-communicate-with) under SYSTEM TESTS.
  6. Establish communication with the PCM/VCM. Access any DTCs that may by present. If no DTCs are present, go to next step. For DTC U1026, see «DTC U1026: LOSS OF TRANSFER CASE SHIFT CONTROL MODULE CLASS 2 COMMUNICATION»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system) under DIAGNOSTIC TESTS. For DTC U1041 see «DTC U1041: LOSS OF EBCM COMMUNICATION»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system) under DIAGNOSTIC TESTS. For DTC U1192 see «DTC U1192: LOSS OF EVO/PASSLOCK™ CLASS 2 COMMUNICATION»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system) under DIAGNOSTIC TESTS. If there is no communication with the scan tool, see «SCAN TOOL DOES NOT COMMUNICATE WITH PCM»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__scan-tool-does-not-communicate-with) or «SCAN TOOL DOES NOT COMMUNICATE WITH VCM»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__scan-tool-does-not-communicate-with) under SYSTEM TESTS.
  7. Establish communication with the ATCM. Access any DTCs that may be present. If no DTCs are present, go to next step. For DTC U1016, see «DTC U1016: LOSS OF COMMUNICATIONS WITH PCM/VCM»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system) under DIAGNOSTIC TESTS. For DTC U1041, see «DTC U1041: LOSS OF EBCM COMMUNICATION»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system) under DIAGNOSTIC TESTS.
  8. Establish communication with the EVO/Passlock™ module. Access any DTCs that may be present. For DTC U1016, see «DTC U1016: LOSS OF COMMUNICATIONS WITH PCM/VCM»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system) . For DTC U1255, see «DTC U1255: SERIAL DATA LINE MALFUNCTION»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system) .

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DTC (1)Description
U1016Loss Of Communications With PCM
U1026Loss Of Transfer Case Shift Control Module Class 2 Communication
U1041Loss Of EBCM Communication
U1192Loss Of EVO/Passlock™ Class 2 Communication
U1255Serial Data Line Malfunction
(1) Perform appropriate test under DIAGNOSTIC TESTS . Codes listed in this table are only for testing covered in this article. For a complete list of codes, see appropriate SELF-DIAGNOSTICS INTRODUCTION article in ENGINE PERFORMANCE.
(1)Perform appropriate test under DIAGNOSTIC TESTS . Codes listed in this table are only for testing covered in this article. For a complete list of codes, see appropriate SELF-DIAGNOSTICS INTRODUCTION article in ENGINE PERFORMANCE.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

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Scheme 17: CONNECTOR IDENTIFICATION
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DTC Parameters

  1. Ignition is active.
  2. Communication was present between EVO/Passlock™ module and PCM/VCM for more than one second, then lost for more than 5 seconds.
  3. The PCM/VCM has not received a valid state of health message from the EVO/Passlock™ module.

Action Taken When DTC U1016 Is Set

  1. EVO/Passlock™ module stores DTC U1016.
  2. If ignition was OFF, vehicle will not start.
  3. If engine was running, vehicle will start again. Security indicator will remain lit.

Diagnostic Procedure (PCM - Diesel)

  1. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  2. If communication cannot be established with PCM, go to next step. If communications are established with PCM, go to step 6 .
  3. Turn ignition to OFF. Remove scan tool from DLC. Disconnect connector C3 from PCM. Check for continuity with DVOM between PCM connector terminal C8 and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 5 .
  4. Replace PCM. See «REMOVAL, OVERHAUL & INSTALLATION - TRUCKS»(/cadillac/escalade/gmt400-1998-2000/remont/removal-installation/#engine-controls-removal-installation-trucks) in ENGINE PERFORMANCE article. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  5. Repair open in Purple 1807 circuit wiring between PCM and DLC. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  6. Establish communication with transfer case shift control module. If communication can be established, go to next step. If communication cannot be established, go to step 8 .
  7. Establish communication with EVO/Passlock™ module. If communication can be established, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.. If communication cannot be established, go to step 11 .
  8. Turn ignition to OFF. Remove scan tool from DLC. Disconnect C1 from the transfer case shift control module. Check for continuity with DVOM between transfer case shift control module connector terminal E9 and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 10 .
  9. Replace transfer case shift module. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  10. Repair open or resistance in Purple 1807 circuit wiring between transfer case shift control module and S280. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  11. Turn ignition to OFF. Remove scan tool from DLC. Disconnect the connector from the EVO/Passlock™ module. Check for continuity with DVOM between EVO/Passlock™ module connector terminal B4 and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 13 .
  12. Replace EVO/Passlock™ module. See appropriate ANTI-THEFT SYSTEMS article.
  13. Repair open or resistance in Purple 1807 circuit wiring between EVO/Passlock™ module and S280. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

If the DTC is in "history" only, the fault may be intermittent. Wiggling the wires and connectors may cause the fault to appear. The EVO/Passlock™ module will move the DTC from "current" to "history" on the next ignition cycle if the conditions causing the fault no longer exist. All EVO/Passlock™ module DTCs will be cleared after 100 ignition cycles if no codes are active. DTCs may be cleared manually with a scan tool.

Diagnostic Procedure (VCM - Gasoline)

  1. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  2. If communication cannot be established with VCM, go to next step. If communications are established with VCM, go to step 6 .
  3. Turn ignition to OFF. Remove scan tool from DLC. Disconnect connector C4 from VCM. Check for continuity with DVOM between VCM connector terminal No. 11 and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 5 .
  4. Replace VCM. See «REMOVAL, OVERHAUL & INSTALLATION - TRUCKS»(/cadillac/escalade/gmt400-1998-2000/remont/removal-installation/#engine-controls-removal-installation-trucks) in ENGINE PERFORMANCE. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  5. Repair open in Purple 1807 circuit wiring between VCM and DLC. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  6. Establish communication with transfer case shift control module. If communication can be established, go to next step. If communication cannot be established, go to step 8 .
  7. Establish communication with EVO/Passlock™ module. If communication can be established, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. If communication cannot be established, go to step 11 .
  8. Turn ignition to OFF. Remove scan tool from DLC. Disconnect C1 from the transfer case shift control module. Check for continuity with DVOM between transfer case shift control module connector terminal E9 and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 10 .
  9. Replace transfer case shift module. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  10. Repair open or resistance in Purple 1807 circuit wiring between transfer case shift control module and S280. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  11. Turn ignition to OFF. Remove scan tool from DLC. Disconnect the connector from the EVO/Passlock™ module. Check for continuity with DVOM between EVO/Passlock™ module connector terminal B4 and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 13 .
  12. Replace EVO/Passlock™ module. See appropriate ANTI-THEFT SYSTEMS article.
  13. Repair open or resistance in Purple 1807 circuit wiring between EVO/Passlock™ module and S280. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

If the DTC is in "history" only, the fault may be intermittent. Wiggling the wires and connectors may cause the fault to appear. The EVO/Passlock™ module will move the DTC from "current" to "history" on the next ignition cycle if the conditions causing the fault no longer exist. All DTCs will be cleared after 100 ignition cycles if no codes are active. DTCs may be cleared manually with a scan tool.

Description

The PCM/VCM monitors the class 2 serial data circuit for communications from the transfer case shift control module.

If the transfer case shift control module is not communicating with the PCM/VCM, DTC U1026 will be stored in memory. This DTC will not set unless the PCM/VCM has first established communications with the transfer case shift control module, and can only diagnose an open or intermittent connection from the transfer case shift control module to S280. DTC U1026 does not light the Malfunction Indicator Light (MIL).

Diagnostic Procedures

Note. Do not clear DTCs without first recording freeze frame and failure records data. This information will be erased when the DTCs are cleared.

  1. Perform powertrain OBD system test. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-control-system-tests-wcodes-introduction__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION - GASOLINE - EXCEPT METRO, PRIZM & TRACKER article in ENGINE PERFORMANCE.
  2. Connect a scan tool and turn the ignition to ON. Do not start the engine. Establish communication with the transfer case shift control module. If the transfer case shift control module communicates with the scan tool, go to next step. If the transfer case shift control module cannot communicate with the scan tool, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  3. Check the class 2 data circuit for an open between the PCM/VCM and the transfer case shift control module, a short to ground, a short to voltage or loose or damaged terminals on the DLC, PCM/VCM or the transfer case shift control module. If there is no fault with the wiring or connectors, go to next step. If there is any fault with the wiring or connectors, repair and go to step 5 .
  4. Turn ignition to OFF. Connect any components or connectors that were disconnected. Save freeze frame and failure records data and clear all DTCs with the scan tool. Turn ignition OFF for 15 seconds. Operate the vehicle under the conditions indicated in the failure records. If DTC U1026 does not reset, fault is intermittent. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  5. Turn ignition OFF. Connect any components or connectors that were disconnected. Clear all DTCs with the scan tool. If any DTCs are displayed, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

The DTC will clear after 40 consecutive ignition cycles if there are no failures of any non-emissions related diagnostic tests, if power to the PCM/VCM is interrupted. DTCs can be manually cleared with a scan tool.

If the PCM/VCM has established communications with the EBCM and received a state of health message during the present ignition cycle and then loses communication or does not receive a state of health message for five seconds, DTC U1041 will be stored in the PCM/VCM memory. DTC U1041 does not light the MIL.

Diagnostic Procedure

  1. Ensure transfer case diagnostic system is functioning properly.
  2. Inspect all related wiring and connections, including connections at the PCM/VCM and transfer case shift control module. Check for: Backed out terminals. Faulty mating of connectors. Deformed or damaged terminals. Faulty terminal-to-wiring connections. Damaged wiring harnesses. Corrosion.
  3. If the PCM/VCM is communicating with the scan tool and both PCM/VCM and transfer case shift control module have stored DTC U1041, check the Purple 1807 circuit wire between the ECBM and S150 for an open.
  4. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

The PCM/VCM will move the DTC from "current" to "history" on the next ignition cycle. If the PCM/VCM receives communication from the EBCM for the next 40 consecutive ignition cycles, the DTC will clear. DTCs may be cleared manually with a scan tool.

The EVO/Passlock™ module sends a security password when its ignition 1 input becomes active and includes its source ID with a fuel continue or fuel disable password. The PCM/VCM learns the source ID, monitors state of health messages and replies to the EVO/Passlock™ module with a security status ID. The EVO/Passlock™ module learns the PCM/VCM ID, monitors state of health messages and acknowledges receipt of the PCM/VCM security status message.

If the PCM/VCM has established communications with the EVO/Passlock™ module and received a state of health message during the present ignition cycle and then loses communication or does not receive a state of health message for 5 seconds, DTC U1192 will be stored in the PCM/VCM memory.

Action Taken When DTC U1192 Is Set

When a failure occurs after the PCM/VCM receives a fuel continue password

  1. The vehicle will start.
  2. The PCM/VCM will continue to enable fuel delivery in the "fuel enabled after security fault mode" until the fault is corrected and a valid password is received from the EVO/Passlock™ module. If the fault is corrected and the PCM/VCM receives a valid password, fuel delivery is enabled. The "fail enable active" bit in the PCM/VCM security status ID will now be false and the "fuel continue state" bit will be true.
  3. DTC U1192 will be stored in the PCM/VCM memory. DTC U1192 will not light the MIL.

When a failure occurs with the ignition OFF or before the PCM/VCM has received a security password from the EVO/Passlock™ module during cranking

  1. The vehicle will not start, or stalls shortly after starting.
  2. The PCM/VCM disables fuel delivery until the fault is corrected and a valid password is received from the EVO/Passlock™ module. Fuel delivery is disabled for the current ignition cycle.
  3. DTC U1192 will be stored in the PCM/VCM memory. DTC U1192 will not light the MIL.
  1. Perform powertrain OBD system test. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-control-system-tests-wcodes-introduction__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION - GASOLINE - EXCEPT METRO, PRIZM & TRACKER article in ENGINE PERFORMANCE.
  2. Connect a scan tool to the DLC. Turn the ignition to RUN. If communication can be established with PCM/VCM, go to next step. If communication cannot be established with PCM/VCM, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  3. Turn ignition OFF. Disconnect EVO/Passlock™ module connector and scan tool from DLC. Check the resistance with DVOM between EVO/Passlock™ module connector terminal B4 and DLC connector terminal No. 2. If the resistance is 0-5 ohms, go to next step. If resistance is greater than 5 ohms, go to step 5 .
  4. Replace EVO/Passlock™ module. See appropriate ANTI-THEFT SYSTEMS article. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  5. Repair fault in Purple 1807 circuit wiring between EVO/Passlock™ module and S280. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

The PCM/VCM will move the DTC from "current" to "history" on the next ignition cycle if the fault is not present. If the PCM/VCM establishes communication with the EVO/Passlock™ module and the fault does not occur for 40 consecutive ignition cycles, the DTC will clear. DTCs may be cleared manually with a scan tool.

Diagnostic Aids

Note. Do not clear the DTC unless directed by a diagnostic procedure. Clearing the DTC will also clear freeze frame and failure records information.

  1. Ensure that none of the issues in bulletins TECHNICAL SERVICE BULLETIN dated June 2001 and TECHNICAL SERVICE BULLETIN dated September 2001 are causing symptoms associated with DTC U1192.
  2. Carefully inspect all wiring and connectors for any fault.
  3. If the class 2 serial data line is shorted to ground or voltage, communication with all modules on the data line will be disrupted. After repairing the fault causing DTC U1192, ensure all modules that have loss of communications DTCs stored in them are cleared.
  4. A scan tool diagnostic circuit check status of "active" indicates that a module is communicating with the scan tool. An "inactive" status indicates that a module previously communicated with the scan tool but is not currently communicating. If a module is not listed, the module has not communicated with the scan tool. Applicable modules are listed in «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

This circuit handles all class 2 communication between all modules and between the modules and a scan tool.

If the ignition is active and communication with the DLC and other modules is lost, or has been lost due to intermittent connection, DTC U1255 will be stored in the EVO/Passlock™ memory.

Action Taken When DTC U1255 Is Set

If the ignition was OFF when the DTC was set, the vehicle will not start. If the engine was running when the DTC was set, the vehicle will start again but the security indicator will be lit.

  1. Ensure Passlock™ system is functioning properly. See SYSTEM CHECK in appropriate ANTI-THEFT SYSTEMS article.
  2. Turn the ignition to ON. Connect a scan tool. If communication can be established with the PCM/VCM, go to next step. If communication cannot be established with PCM/VCM, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  3. Turn ignition OFF. Disconnect the EVO/Passlock™ module. Check the resistance with DVOM between EVO/Passlock™ module connector terminal B4 and DLC terminal No. 2. If the resistance is 0-5 ohms, go to next step. If the resistance is greater than 5 ohms, go to step 5 .
  4. Replace the EVO/Passlock™ module. See appropriate ANTI-THEFT SYSTEMS article. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  5. Repair Fault in Purple 1807 circuit wiring between EVO/Passlock™ module and DLC. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

If the DTC is in "history" only, the fault may be intermittent. Wiggling the wires and connectors may cause the fault to appear. The EVO/Passlock™ module will move the DTC from "current" to "history" on the next ignition cycle if the conditions causing the fault no longer exist. All EVO/Passlock™ module DTCs will be cleared after 100 ignition cycles if no codes are active. DTCs may be cleared manually with a scan tool.

SCAN TOOL INOPERATIVE

  1. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  2. Ensure scan tool is operating correctly by connecting scan tool to a different vehicle. If scan tool is functioning properly, return to original vehicle and go to next step. If scan tool is malfunctioning, refer to scan tool owners manual.
  3. Ensure ignition is OFF. Connect a test lamp between DLC terminal No. 16 and ground. If the test lamp lights, go to next step. If the test light does not light, go to step 6 .
  4. Connect a test lamp between DLC terminals No. 16 and 4, then between DLC terminals No. 16 and 5. If the test lamp lights on both tests, go to next step. If the test lamp does not light on both tests, go to step 7 .
  5. Inspect the DLC power and ground circuits for intermittent or poor connections. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  6. Repair open in the Orange 840 circuit wiring between the AUX POWER fuse and the DLC. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  7. Repair open in the Black 150 circuit or the Black/White 451 circuit wiring between ground and the DLC. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

SCAN TOOL DOES NOT COMMUNICATE WITH EBCM

  1. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ignition OFF. Disconnect scan tool from DLC. Disconnect C1 from EBCM. Check for continuity with DVOM between EBCM terminal "F" and DLC terminal No. 12. If there is continuity, go to next step. If there is no continuity, go to step 4 .
  3. Replace EBCM. See ANTI-LOCK - 4WAL - RWD TRUCKS - EXCEPT 1999 SIERRA & SILVERADO article in BRAKES. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  4. Repair open or resistance in Tan/White 799 circuit wiring between EBCM and DLC. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

SCAN TOOL DOES NOT COMMUNICATE WITH UART DATA LINE

  1. Perform SIR diagnostic system check. See «SIR DIAGNOSTIC SYSTEM CHECK»(ref-142593-S34509597912002081200000) under DIAGNOSTIC TESTS in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  2. Turn ignition to RUN. Measure voltage with DVOM between DLC terminals No. 4 and 9. If voltage is less than 5 volts, go to next step. If voltage is greater than 5 volts, go to step 5 . If voltage is 5 volts, perform SIR diagnostic system check. See «SIR DIAGNOSTIC SYSTEM CHECK»(ref-142593-S34509597912002081200000) under DIAGNOSTIC TESTS in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  3. Turn ignition to OFF. Check for continuity using DVOM between ground and DLC terminal No. 9. If there is continuity, go to next step. If there is no continuity, go to step 7 .
  4. Repair short to ground in Tan 800 circuit wiring between SDM and DLC. Perform SIR diagnostic system check. See «SIR DIAGNOSTIC SYSTEM CHECK»(ref-142593-S34509597912002081200000) under DIAGNOSTIC TESTS in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  5. Disconnect SDM connector. Turn ignition to RUN. Check voltage using DVOM between ground and DLC terminal No. 9. If voltage is greater than 0 volts, go to next step. If voltage is 0 volts, go to step 7 .
  6. Repair short to voltage in Tan 800 circuit wiring between SDM and DLC. Perform SIR diagnostic system check. See «SIR DIAGNOSTIC SYSTEM CHECK»(ref-142593-S34509597912002081200000) under DIAGNOSTIC TESTS in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  7. Perform SDM integrity check. See «SDM INTEGRITY CHECK»(ref-142593-S10713644332002081200000) under DIAGNOSTIC TESTS in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS. If SDM checks faulty, replace SDM. See «REMOVAL & INSTALLATION»(ref-142593-S11833764142002081200000) in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.

SCAN TOOL DOES NOT COMMUNICATE WITH VCM

  1. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ignition RUN. If MIL lights, go to next step. If MIL does not light, perform powertrain OBD system test. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/testing-diagnostics/#engine-control-system-tests-wcodes-introduction__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION - GASOLINE - EXCEPT METRO, PRIZM & TRACKER article in ENGINE PERFORMANCE.
  3. Select "powertrain diagnostics" on scan tool main menu. If scan tool indicates "no data communication with vehicle" go to next step. If scan tool does not indicate "no data communication with vehicle" perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  4. Select "chassis diagnostics" on scan tool main menu. If scan tool can communicate with EBCM, go to next step. If scan tool cannot communicate with EBCM, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  5. Turn ignition OFF. Disconnect connector C4 from VCM. Check for continuity with DVOM between VCM connector terminal No. 11 and S150. If there is no continuity, go to next step. If there is continuity, go to step 7 .
  6. Repair open or resistance in Purple 1807 circuit wiring between VCM connector terminal 11 and S150. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  7. Replace VCM. See «REMOVAL, OVERHAUL & INSTALLATION - TRUCKS»(/cadillac/escalade/gmt400-1998-2000/remont/removal-installation/#engine-controls-removal-installation-trucks) article in ENGINE PERFORMANCE article. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

SCAN TOOL DOES NOT COMMUNICATE WITH PCM

  1. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ignition RUN. If ABS indicator lights, go to next step. If ABS indicator does not light, perform ABS diagnostic system test. See «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/anti-locktraction-control/#anti-lock-brake-system__diagnostic-system-check) under DIAGNOSIS & TESTING in ANTI-LOCK - 4WAL - RWD TRUCKS - EXCEPT 1999 SIERRA & SILVERADO article in BRAKES.
  3. Select "chassis diagnostics" on scan tool main menu. If scan tool can communicate with EBCM, go to next step. If scan tool cannot communicate with EBCM, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  4. Select "powertrain diagnostics" on scan tool main menu. If scan tool cannot communicate with PCM, go to next step. If scan tool can communicate with PCM, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  5. Turn ignition OFF. Disconnect connector C3 from PCM. Check for continuity with DVOM between PCM connector terminal C8 and splice S150. If there is continuity, go to next step. If there is no continuity, go to step 7 .
  6. Replace PCM. See «REMOVAL, OVERHAUL & INSTALLATION - TRUCKS»(/cadillac/escalade/gmt400-1998-2000/remont/removal-installation/#engine-controls-removal-installation-trucks) article in ENGINE PERFORMANCE article. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  7. Repair open or resistance in Purple 1807 circuit wiring between EBCM and S107. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DATA LINE

  1. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  2. Disconnect scan tool from DLC. Turn ignition to RUN. Check voltage with DVOM between DLC terminals No. 2 and 4. If voltage is greater than 7 volts, go to next step. If voltage is not greater than 7 volts, go to step 10 .
  3. Turn ignition OFF. Disconnect C100. Check voltage with DVOM between DLC terminals No. 2 and 4. If voltage is not greater than 7 volts, go to next step. If voltage is greater than 7 volts, go to step 6 .
  4. Turn ignition OFF. Connect C100. Disconnect EBCM connector C1. Check voltage with DVOM between DLC terminals No. 2 and 4. If voltage is greater than 7 volts, go to next step. If voltage is not greater than 7 volts, go to step 18 .
  5. Turn ignition OFF. Disconnect PCM/VCM. Check voltage with DVOM between DLC terminals No. 2 and 4. If voltage is greater than 7 volts, go to step 8 . If voltage is not greater than 7 volts, go to step 18 .
  6. Turn ignition OFF. Disconnect EVO/Passlock™ module. Check voltage with DVOM between DLC terminals No. 2 and 4. If voltage is greater than 7 volts, go to next step. If voltage is not greater than 7 volts, go to step 18 .
  7. Turn ignition OFF. Disconnect transfer case shift module connector C1. Check voltage with DVOM between DLC terminals No. 2 and 4. If voltage is greater than 7 volts, go to step 9 . If voltage is not greater than 7 volts, go to step 18 .
  8. Repair short to voltage in Purple 1807 circuit wiring between C100 and EBCM and PCM/VCM. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) .
  9. Repair short to voltage in Purple 1807 circuit wiring between DLC and EVO/Passlock™ module, C100 and transfer case shift module. Connect C100. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  10. Turn the ignition OFF. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  11. Disconnect C100. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is no continuity, go to next step. If there is continuity, go to step 14 .
  12. Reconnect C100. Disconnect EBCM connector C1. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 18 .
  13. Disconnect the PCM/VCM. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is continuity, go to step 16 . If there is no continuity, go to step 18 .
  14. Disconnect EVO/Passlock™ module. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is continuity, go to next step. If there is no continuity, go to step 18 .
  15. Disconnect transfer case shift control module connector C1. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is continuity, go to step 17 . If there is no continuity, go to step 18 .
  16. Repair short to ground in Purple 1807 wiring between C100 and EBCM and PCM/VCM. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  17. Repair short to ground in Purple 1807 wiring between DLC and EVO/Passlock™ module, C100 and transfer case shift control module. Connect C100. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
  18. Replace module most recently disconnected. Perform «DIAGNOSTIC SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/communication-devices/#data-link-communications-system__diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

SCAN TOOL DOES NOT COMMUNICATE WITH ENTERTAINMENT & COMFORT DATA LINE

Turn ignition OFF. Disconnect scan tool and radio connector C2. Check for continuity between radio connector terminal No. 15 and DLC terminal No. 14. If there is continuity, replace radio. If there is no continuity, repair open or cause of resistance in Dark Green 835 circuit wiring between radio and DLC.

Computer Data Lines (Escalade, Pickup, Suburban). Scheme 22

Scheme 22: Computer Data Lines (Escalade, Pickup, Suburban)
Scheme 22: Computer Data Lines (Escalade, Pickup, Suburban)