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Scan Tool Does Not Communicate With Class 2 Device: Testing

  1. Connect scan tool to Data Link Connector (DLC). If scan tool powers up, go to next step. If scan tool does not power up, go to SCAN TOOL DOES NOT POWER UP  .
  2. Turn ignition on. Attempt to communicate with each module on class 2 serial data line. If scan tool communicates with one or more modules, go to next step. If scan tool does not communicate with any module, go to step  5 .
  3. Retrieve DTCs for each module. Record DTCs, DTC status and which module set the DTC(s). If any DTCs between DTC U1000 and U1255 are set, go to next step. If any DTCs between DTC U1000 and U1255 are not set, test is complete. Fault may be intermittent.
  4. If DTC U1000 is set, go to DTC U1000 OR U1255: CLASS 2 COMMUNICATION MALFUNCTION  under DIAGNOSTIC TESTS. If DTC U1000 is not set, perform appropriate test. See BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX  table.
  5. Turn ignition off. Disconnect scan tool from DLC. Inspect DLC terminals No. 2 and 5 for poor connections and terminal tension. See Fig 1 . Repair as necessary and go to step  17 . If terminals are okay, go to next step.
  6. Check for open circuit between ground point G102 and DLC terminal No. 5 (Black/White wire). See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair as necessary and go to step  17 . If circuit is okay, go to next step.
  7. Disconnect left Instrument Panel (IP) junction block connector C1. Inspect connector for poor connections and poor terminal tension. Repair as necessary and go to step  17 . If connector is okay, go to next step.
  8. Check for open in Purple wire between DLC terminal No. 2 and left IP junction block harness connector C1 terminal D2. See Fig 1 and Fig 2 . Repair as necessary and go to step  17 . If circuit is okay, go to next step.
  9. Check for open or short between left IP junction block connector C1 (component side) terminals D2, A3 and E3. See Fig 2 . Continuity should exist between all 3 terminals. Repair or replace left IP junction block as necessary. Go to step  17 . If left IP junction block is okay, go to next step.
  10. Turn ignition off. Disconnect BCM harness connectors. Check for short to ground and short to voltage in Purple wire between left IP junction block harness connector C1 terminal D2 and BCM harness connector C3 terminal B2. See Fig 2 and Fig 3 . Repair circuit as necessary and go to step  17 . If circuit is okay, go to next step.
  11. Turn ignition off. Disconnect Sensing and Diagnostic Module (SDM) harness connector. Check for short to ground and short to voltage in Purple wire between left IP junction block harness connector C1 terminal E3 and SDM harness connector terminal A4. Repair circuit as necessary and go to step  17 . If circuit is okay, go to next step.
  12. Turn ignition off. Disconnect Electronic Brake Control Module (EBCM) harness connector. Check for short to ground and short to voltage in Purple wire between left IP junction block harness connector C1 terminal E3 and EBCM harness connector terminal No. 12. Repair circuit as necessary and go to step  17 . If circuit is okay, go to next step.
  13. Turn ignition off. Disconnect Powertrain Control Module (PCM) harness connector. Check for short to ground and short to voltage in Purple wire between left IP junction block harness connector C1 terminal A3 and PCM harness connector C1 terminal No. 59 (2.4L engine) or No. 58 (3.4L engine). Repair circuit as necessary and go to step  17 . If circuit is okay, go to next step.
  14. Turn ignition off. Disconnect Instrument Panel Cluster (IPC) harness connector. Check for short to ground and short to voltage in Purple wire between left IP junction block harness connector C1 terminal A3 and IPC harness connector terminal A9 (on Grand Am) or B1 (on Alero). Repair circuit as necessary and go to step  17 . If circuit is okay, go to next step.
  15. Check for poor connections and terminal tension at connector for each module that is not communicating. Repair connector as necessary and go to step  17 . If connector is okay, go to next step.
  16. Replace module that is not communicating. See appropriate procedure under REMOVAL & INSTALLATION  .
  17. Reconnect all harness connectors. Connect scan tool to DLC. Turn ignition on. Wait 10 seconds. Scan tool may require a power up reset before communication will occur if class 2 serial data line was shorted. Turn off and disconnect scan tool. Reconnect scan tool and retrieve DTCs from each module. Record DTCs and DTC status. If any current DTCs beginning with a "U" are present, go to step  19 . If no current DTCs beginning with a "U" are present, go to next step.
  18. If any DTCs not beginning with a "U" are present, go to next step. If no DTCs not beginning with a "U" are present, go to step  21 .
  19. Perform appropriate diagnostic procedure. See BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX  table. For DTCs not listed, attempt to diagnose malfunctioning system or device by symptom. Go to appropriate article for malfunctioning system or device. Go to next step.
  20. If all DTCs have been diagnosed, go to next step. If any DTCs have not been diagnosed, go to step  19 .
  21. Using scan tool, clear DTCs. System is okay at this time.
Fig 1: Identifying Data Link Connector Terminals
G00016046Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying Left IP Junction Block Harness Connectors & Terminals
G00016048Courtesy of GENERAL MOTORS CORP.
Fig 3: Identifying BCM Connectors & Terminals
G99F08621Courtesy of GENERAL MOTORS CORP.
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