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Data Link Communications System - Old Style: Diagnosis GMC Yukon Denali

Communication Devices 5 illustrations ~2842 words

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 .

SELF DIAGNOSTIC SYSTEM

WARNINGVehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see AIR BAG RESTRAINT SYSTEMS - WITH SIDE AIR BAG or AIR BAG RESTRAINT SYSTEMS - WITHOUT SIDE AIR article in RESTRAINTS.

For information on how to retrieve and clear DTCs, see scan tool instruction manual and SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - GASOLINE or SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - DIESEL article in ENGINE PERFORMANCE.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DTC (1)Description
U1016 (2)Loss Of Communications With PCM/VCM
U1026 (3)Loss Of Automatic Transfer Case Control Module Class 2 Communication
U1041 (3)Loss Of EBCM Communication
U1192 (3)Loss Of EVO/Passlock™ Class 2 Communication
U1255 (2)Serial Data Line Malfunction
U1300 (4)Class 2 Data Line Voltage Is Low
U1301 (4)Class 2 Data Line Voltage Is High
U1500Inter-Device Dedicated Bus 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 SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - GASOLINE or SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - DIESEL article. (2) For diagnostic procedures, see DIAGNOSTIC TESTS in appropriate ANTI-THEFT SYSTEMS article. (3) For diagnostic procedures, see SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - GASOLINE or SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - DIESEL article. (4) For diagnostic procedures, see DIAGNOSTIC TESTS in BODY CONTROL MODULES - ESCALADE, TAHOE & YUKON DENALI article.
(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 SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - GASOLINE or SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - DIESEL article.
(2)For diagnostic procedures, see DIAGNOSTIC TESTS in appropriate ANTI-THEFT SYSTEMS article.
(3)For diagnostic procedures, see SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - GASOLINE or SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - DIESEL article.
(4)For diagnostic procedures, see DIAGNOSTIC TESTS in BODY CONTROL MODULES - ESCALADE, TAHOE & YUKON DENALI article.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE

See TEST C: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in ANTI-LOCK article in BRAKES (for Cab & Chassis & Pickup) or SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in BODY CONTROL MODULES article (for Escalade, Tahoe Limited & Z71 & Yukon Denali).

SCAN TOOL INOPERATIVE

The data link connector (DLC) provides operating power for the scan tool at terminal 16 (battery positive voltage) and at terminal 4 (ground). The DLC provides the class 2 serial data signal at terminal 2 and signal ground at terminal 5. The scan tool will power up with the ignition off. Many modules, however, will not communicate unless the body control module (BCM) detects that the ignition is on and sends the appropriate power mode message.

  1. Test the battery positive voltage circuit of the DLC for an open or a short to ground. If there is no fault, go to next step.
  2. Test the ground circuit at terminal 4 of the DLC for an open or a short to ground. If there is no fault, go to next step.
  3. Inspect for poor connections at terminals 4 and 16 of the DLC. If there is no fault, go to next step.
  4. The scan tool may be malfunctioning. Refer to the scan tool user guide.

SCAN TOOL DOES NOT COMMUNICATE WITH EBCM

  1. Perform anti-lock brake system diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK»(ref-63582-S33427129072001021700000) in ANTI-LOCK BRAKES article.
  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 «ELECTRONIC BRAKE CONTROL MODULE»(ref-63582-S00307899012001021700000) in ANTI-LOCK article in BRAKES. Perform anti-lock brake system diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK»(ref-63582-S33427129072001021700000) in ANTI-LOCK article in BRAKES.
  4. Repair open or resistance in Tan/White 799 circuit wiring between EBCM and DLC. Perform anti-lock brake system diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK»(ref-63582-S33427129072001021700000) in ANTI-LOCK article in BRAKES.

SCAN TOOL DOES NOT COMMUNICATE WITH UART DATA LINE

  1. Perform SIR diagnostic system check. See «SIR DIAGNOSTIC SYSTEM CHECK»(ref-97269-S03737713362001043000000) in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS.
  2. Turn ignition to RUN. Measure voltage with DVOM between DLC terminal Nos. 4 and 9. If voltage is less than 4-5 volts, go to next step. If voltage is greater than 4-5 volts, go to step 5 . If voltage is 4-5 volts, perform SIR diagnostic system check. See «SIR DIAGNOSTIC SYSTEM CHECK»(ref-97269-S03737713362001043000000) in AIR BAG RESTRAINT SYSTEMS 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 not 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-97269-S03737713362001043000000) in AIR BAG RESTRAINT SYSTEMS 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-97269-S03737713362001043000000) in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS.
  7. Perform SDM integrity check. See «SDM INTEGRITY CHECK»(ref-97269-S05104093682001043000000) in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS. If SDM checks faulty, replace SDM. See «SENSING & DIAGNOSTIC MODULE (SDM)»(ref-97269-S30301542612001043000000) in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS. Perform SIR diagnostic system check. See «SIR DIAGNOSTIC SYSTEM CHECK»(ref-97269-S03737713362001043000000) in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS.

SCAN TOOL DOES NOT COMMUNICATE WITH VCM

  1. Turn ignition RUN. If MIL lights, go to next step. If MIL does not light, perform powertrain OBD system test. See appropriate OBD SYSTEM TEST in SELF DIAGNOSTICS INTRODUCTION article.
  2. 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", see «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(ref-147986-S29256757302002091900000) .
  3. Select "chassis diagnostics" on scan tool main menu. If scan tool can communicate with EBCM, go to next step. If scan tool can not communicate with EBCM, perform anti-lock brakes diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK»(ref-63582-S33427129072001021700000) in appropriate ANTI-LOCK article in BRAKES.
  4. 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 6 .
  5. Repair open or resistance in Purple 1807 circuit wiring between VCM connector terminal No. 11 and S150. Perform powertrain OBD system test. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-9430-S38744735792000102300000) in SELF DIAGNOSTICS - GASOLINE or «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-3911-S11171477082000052300000) in SELF DIAGNOSTICS - DIESEL article in TESTING & DIAGNOSIS in ENGINE PERFORMANCE.
  6. Replace VCM. See «POWERTRAIN CONTROL MODULE»(ref-4644-S31636836302000071100000) in REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Perform powertrain OBD system test. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-9430-S38744735792000102300000) in SELF DIAGNOSTICS - GASOLINE or «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-3911-S11171477082000052300000) in SELF DIAGNOSTICS - DIESEL article in TESTING & DIAGNOSTICS in ENGINE PERFORMANCE.

SCAN TOOL DOES NOT COMMUNICATE WITH PCM

  1. Turn ignition RUN. If ABS indicator lights, go to next step. If ABS indicator does not light, perform ABS diagnostic system test. See appropriate «DIAGNOSTIC SYSTEM CHECK»(ref-63582-S33427129072001021700000) in ANTI-LOCK article in BRAKES.
  2. Select "chassis diagnostics" on scan tool main menu. If scan tool can communicate with EBCM, go to next step. If scan tool can not communicate with EBCM, see «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(ref-147986-S29256757302002091900000) .
  3. 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, see «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(ref-147986-S29256757302002091900000) .
  4. Turn ignition OFF. Disconnect connector C3 from PCM. Check for continuity with DVOM between PCM connector terminal No. C8 and S150. If there is continuity, go to next step. If there is no continuity, go to step 6 .
  5. Replace PCM. See «POWERTRAIN CONTROL MODULE»(ref-4644-S31636836302000071100000) in REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Perform powertrain OBD system test. See appropriate «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-9430-S38744735792000102300000) in SELF DIAGNOSTICS - GASOLINE or «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-3911-S11171477082000052300000) in SELF DIAGNOSTICS - DIESEL article in TESTING & DIAGNOSTICS in ENGINE PERFORMANCE.
  6. Repair open or resistance in Purple 1807 circuit wiring between EBCM and S107. Perform powertrain OBD system test. See appropriate «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-9430-S38744735792000102300000) in SELF DIAGNOSTICS - GASOLINE or «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-3911-S11171477082000052300000) in SELF DIAGNOSTICS - DIESEL in TESTING & DIAGNOSTICS in ENGINE PERFORMANCE.

SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DATA LINE

  1. Disconnect scan tool from DLC. Turn ignition to RUN. Check voltage with DVOM between DLC terminal Nos. 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 9 .
  2. Turn ignition OFF. Disconnect C100. Check voltage with DVOM between DLC terminal Nos. 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 5 .
  3. Turn ignition OFF. Connect C100. Disconnect EBCM connector C1. Check voltage with DVOM between DLC terminal Nos. 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 17 .
  4. Turn ignition OFF. Disconnect PCM/VCM. Check voltage with DVOM between DLC terminal Nos. 2 and 4. If voltage is greater than 7 volts, go to step 7 . If voltage is not greater than 7 volts, go to step 17 .
  5. Turn ignition OFF. Disconnect EVO/Passlock™ module. Check voltage with DVOM between DLC terminal Nos. 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 17 .
  6. Turn ignition OFF. Disconnect transfer case shift module connector C1. Check voltage with DVOM between DLC terminal Nos. 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 17 .
  7. Repair short to voltage in Purple 1807 circuit wiring between C100 and EBCM and PCM/VCM. Perform diagnostic system check for EBCM and PCM/VCM. See «DIAGNOSTIC SYSTEM CHECK»(ref-63582-S33427129072001021700000) in ANTI-LOCK BRAKES and «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-9430-S38744735792000102300000) in SELF DIAGNOSTICS - GASOLINE or «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-3911-S11171477082000052300000) in SELF DIAGNOSTICS - DIESEL in TESTING & DIAGNOSTICS in ENGINE PERFORMANCE.
  8. 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 for EVO/Passslock™ module and transfer case shift module. See «DIAGNOSTIC SYSTEM CHECK»(ref-3748-S06767826942000051200000) in ANTI-THEFT SYSTEMS article and «TRANSFER CASE SYSTEM CHECK»(ref-91302-S04636611162001030700000) in TRANSFER CASE article in TRANSAXLE/TRANSMISSION.
  9. 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 not continuity, perform diagnostic system check for all modules on 1807 circuit. See appropriate DIAGNOSTIC SYSTEM CHECK section or article.
  10. Disconnect C100. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is not continuity, go to next step. If there is continuity, go to step 13 .
  11. 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 not continuity, go to step 17 .
  12. Disconnect the PCM/VCM. Check for continuity with DVOM between ground and DLC terminal No. 2. If there is continuity, go to step 15 . If there is not continuity, go to step 17 .
  13. 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 not continuity, go to step 17 .
  14. 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 16 . If there is not continuity, go to step 17 .
  15. Repair short to ground in Purple 1807 wiring between C100 and EBCM and PCM/VCM. Perform diagnostic system check for EBCM and PCM/VCM. See «DIAGNOSTIC SYSTEM CHECK»(ref-63582-S33427129072001021700000) in appropriate ANTI-LOCK article in BRAKES and «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-9430-S38744735792000102300000) in SELF DIAGNOSTICS - GASOLINE or «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-3911-S11171477082000052300000) in SELF DIAGNOSTICS - DIESEL article in TESTING & DIAGNOSTICS in ENGINE PERFORMANCE.
  16. 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 for EVO/Passlock™ module and transfer case shift control module. See «DIAGNOSTIC SYSTEM CHECK»(ref-3748-S06767826942000051200000) in ANTI-THEFT SYSTEMS and «TRANSFER CASE SYSTEM CHECK»(ref-91302-S04636611162001030700000) in TRANSFER CASE article in TRANSAXLE/TRANSMISSION.
  17. Replace module most recently disconnected. Perform diagnostic system check for all modules on 1807 circuit. See Appropriate DIAGNOSTIC SYSTEM CHECK in appropriate system article.

SCAN TOOL DOES NOT COMMUNICATE WITH ENTERTAINMENT & COMFORT DATA LINE

  1. Ensure audio system functions properly.
  2. Test the entertainment & comfort data circuit for an open or high resistance. If there is no fault, go to next step.
  3. Disconnect the vehicle interface module (VIU). With the scan tool, attempt to communicate with the radio. If communication can not be established with the radio, go to next step. If communication can be established with the radio, go to step 5 .
  4. Replace the radio.
  5. Replace the VIU. The VIU must be reprogrammed. Contact the OnStar® Dealer Support line by pressing the OnStar® button twice. The 10-digit STID number recorded will be needed by the OnStar® Dealer Support line. Go to next step.

Scheme 1

Scheme 1: CONNECTOR IDENTIFICATION
Scheme 1: CONNECTOR IDENTIFICATION

DIAGNOSTIC TESTS

WARNINGVehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see AIR BAG RESTRAINT SYSTEMS - WITH SIDE AIR BAG or AIR BAG RESTRAINT SYSTEMS - WITHOUT SIDE AIR article in RESTRAINTS.

DTC Parameters

The Vehicle Interface Unit (VIU) will run this test every 300 ms. The DTC U1500 is set when the VIU detects no communication between the VIU and the Vehicle Communication Unit (VCU). The ignition must be in the RUN or ACC position. Battery voltage must be between 9.5 and 15.5 volts.

Action Taken When DTC U1500 Is Set

When DTC U1500 is current the VIU does not communicate with the VCU. No calls can be placed.

Diagnostic Procedure

  1. Connect scan tool. If scan tool does not power up, see «SCAN TOOL DOES NOT POWER UP»(ref-9118-S26580573542000100500000) in BODY CONTROL MODULES article. Turn ON the ignition, with the engine OFF. Attempt to establish communication with the Vehicle Interface Unit (VIU). If scan tool does not communicate with VIU, see «DTC U1XXX: LOSS OF XXX COMMUNICATION»(ref-9118-S22748180292000100500000) in BODY CONTROL MODULES article. Select the "Vehicle Interface Unit (VIU) display DTCs" function on the scan tool. If scan tool displays any DTCs with a "U" prefix, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-147986-S19621467602002092000000) . If scan tool displays other DTCs, diagnose accordingly.
  2. Turn the ignition OFF. Disconnect the VCU connector. Turn ON the ignition, with the engine OFF. Measure the voltage from the RTN serial data circuit to a good ground. If voltage is greater than 0.04 V, go to next step. If voltage is equal to or less than 0.04 V, go to step 6 .
  3. Measure the voltage from the CMP serial data circuit to a good ground. If voltage is greater than 5 V, go to next step. If voltage is not greater than 5 V, go to step 7 .
  4. Measure the voltage from the TRU serial data circuit to a good ground. If voltage is greater than 5 V, go to next step. If voltage is not greater than 5 V, go to step 8 .
  5. Measure the voltage from the battery positive voltage circuit from the VIU to the VCU to a good ground. If the voltage is not greater than 10 V, go to step 9 . If the voltage is greater than 10 V, go to step 10 .
  6. Test the RTN serial data circuit for a short to ground. If there is not a short to ground, go to step 12 . If there is a short to ground, repair and go to step 13 .
  7. Test the CMP serial data circuit for a short to ground. If there is not a short to ground, go to step 12 . If there is a short to ground, repair and go to step 13 .
  8. Test the TRU serial data circuit for a short to ground. If there is not a short to ground, go to step 12 . If there is a short to ground, repair and go to step 13 .
  9. Test the battery positive voltage circuit for an open. If there is not an open, go to step 12 . If there is an open, repair and go to step 13 .
  10. Test the RTN serial data, CMP serial data and TRU serial data lines for a short to voltage. If there is no short to voltage, go to next step. If there is a short to voltage, repair and go to step 13 .
  11. Replace the VCU. The VCU must be reprogrammed. Press and hold the "end call" button, which is a black button with a white dot. The OnStar® status light will change from green to red to green. Contact the OnStar® Dealer support line by pressing the blue OnStar® button twice. The 11-digit ESN number will be needed by the OnStar® advisor. Go to step 13 .
  12. Replace the VIU. The VIU must be reprogrammed. Contact the OnStar® Dealer Support line by pressing the OnStar® button twice. The 10-digit STID number recorded will be needed by the OnStar® Dealer Support line. Go to next step.
  13. Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. If DTC U1500 does not reset, system is okay. If DTC U1500 does reset, go to step 2 .

Identifying Computer Data Lines. Scheme 2

Scheme 2: Identifying Computer Data Lines
Scheme 2: Identifying Computer Data Lines

Scheme 3

Scheme 3
Scheme 3

Scheme 4

Scheme 4
Scheme 4

Scheme 5

Scheme 5
Scheme 5

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