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HOMESERVICE MANUALSOLDSMOBILE2004BRAVADA RWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 6 (ANTI-LOCK BRAKE SYSTEM - 4WAL)SYMPTOM TESTSTEST C: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE
2004 Oldsmobile Bravada RWD

Test C: Scan Tool Does Not Communicate With Class 2 Device

2004 Oldsmobile Bravada RWDSECTION Test C: Scan Tool Does Not Communicate With Class 2 Device
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2001 GMC Savana Special, 2001 GMC Savana Camper Special, 2001 GMC Savana, 2001 Chevrolet Chevy Express, and 2000 GMC Savana Special. However, it is still accessible from the selected car via links, so may be relevant.
  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, diagnose data link connector circuit. See DATA LINK CONNECTOR article in WIRING DIAGRAMS.
  2. Turn ignition off, with engine off. Using scan tool, attempt to communicate with each module on the class 2 serial data circuit. If scan tool communicates with any module on the class 2 serial data circuit, go to next step. If scan tool does not communicate with any module on the class 2 serial data circuit, go to step  6 .
  3. Using scan tool, select display DTCs function for each module. Record all of displayed DTCs, DTC status and module which set the DTC. If recorded DTCs are in the range of U1000 to U1255, go to next step. If recorded DTCs are not DTC U1000 to U1255, go to step  5 .
  4. If DTC U1000 or U1255 is the only DTC displayed, go to next step. If DTC U1000 or U1255 is not displayed, go to DTC U1001-U1254 in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  5. Diagnose and repair DTC U1001-U1254. Go to appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  6. Turn ignition off. Disconnect scan tool from DLC. Check for poor connections at DLC terminals No. 2 and 5. Repair as necessary. If connections are okay, go to next step.
  7. Check for open in DLC ground circuits. Repair as necessary. After repairs, go to next step.
  8. Disconnect EBCM harness connector C1. Check class 2 serial data circuit (Purple wire) for an open between DLC terminal No. 2 and EBCM harness connector C1 terminal "G" (Purple wire). Repair as necessary. If circuit is okay, go to next step.
  9. Leave EBCM disconnected. Turn ignition on, with engine off. Using scan tool, attempt to establish communications with Vehicle Control Module (VCM) or Powertrain Control Module (PCM). If scan tool communicates with PCM/VCM, go to step  11 . If scan tool does not communicate with PCM/VCM, go to next step.
  10. Turn ignition off. Disconnect PCM or VCM harness connector. Turn ignition on, with engine off. Using scan tool, attempt to establish communications with Passlock(R) module. If scan tool communicates with module, go to step  12 . If scan tool does not communicate with module, go to step  13 .
  11. Check for poor connections at EBCM harness connector. Repair as necessary. After repairs, go to step  17 . If connections are okay, go to step  14 .
  12. Check for poor connections at PCM/VCM harness connector. Repair as necessary. After repairs, go to step  17 . If connections are okay, go to step  15 .
  13. Check for poor connections at Passlock(R) module. Repair as necessary. After repairs, go to step  17 . If connections are okay, go to step  16 .
  14. Replace EBCM. After replacing EBCM, go to step  17 .
  15. Replace PCM/VCM. After replacing PCM/VCM, go to step  17 .
  16. Replace Passlock(R) module. After replacing module, go to next step.
  17. Reconnect all disconnected modules and connectors. Install scan tool. Turn ignition on, with engine off. Wait 10 seconds. Scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn off or disconnect scan tool prior to performing this test. Using scan tool, select display DTCs function for each module. Record all of displayed DTCs and DTC status. If any recorded DTCs begin with a "U" and with a current status, go to step  19 . If recorded DTCs does not begin with a "U" or is not a current status, go to next step.
  18. If any of recorded DTCs do not begin with a "U", go to next step. If no DTCs are recorded, clear DTCs using scan tool.
  19. Diagnose affected DTCs. After repairs, clear DTCs using scan tool.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.